Abstract

Optical polarization characteristics and light extraction behavior of deep-ultraviolet (DUV) light-emitting diode (LED) flip-chip with full-spatial omnidirectional reflector (FSODR) have been investigated. FSODR is fabricated to be simultaneously covered on the whole flip-chip, except the sapphire surface. It is found that the FSODR greatly enhance both transverse-electric (TE) and transverse-magnetic (TM) mode light extraction at every space angle, resulting in total enhancement of 73.1% and 79.8%, respectively. Moreover, the four individual ODR structures separated from FSODR, which are covered on the surface of n-AlGaN, the interface of p-GaN/p-AlGaN, the sidewall of mesa and the sidewall of n-AlGaN/AlN, respectively, show considerably different optical polarization characteristics and extraction behaviors between each other. The achievements of FSODR cannot be obtained by any separated ODR, and all of the individual ODRs can contribute to the FSODR. Especially, the synergy effect of TM extraction behavior obviously exists in FSODR. As a result, the light extraction efficiency (LEE) enhancement of FSODR is approximately 60% at a high current density of 140A/cm2. This study is significant for understanding and modulating the extraction behavior of polarized light to realize high efficiency AlGaN-based DUV LEDs.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1. Introduction

AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) have attracted considerable attentions for the potential applications, including sterilization, water purification, medical phototherapy, secure communication and so on [1–3]. However,the applications are currently obstructed by the low external quantum efficiency (EQE), which decreases rapidly as the wavelength becomes shorter (by increasing the Al content in the AlxGa1-xN) [4,5]. It is well known that the poor light extraction efficiency (LEE) can be dominantly responsible for the low EQE [6]. According to the spin–orbit and crystal-field splitting effects, the predominant optical polarization of light emission leads to the TE (E⊥c) mode for GaN and TM (E∥c) mode for AlN [7,8]. Therefore, the predominant optical polarization switched from TE to TM mode with Al composition increasing for the AlGaN-based DUV-LEDs will cause stronger total internal reflection (TIR) and stronger photons absorption. The optical polarization characteristics determine the extraction behavior and play an important role in the LEE of DUV-LEDs. The effects of optical polarization on LEE have been extensively studied through experiments or simulation methods, including the internal strain, quantum well structure, injection current, light propagation path and so on [9–17]. However, the study of the relationship between full-spatial reflection system, optical polarization characterization and light extraction behavior is lacked, especially at the chip level.

For the chip level, a variety of strategies have been reported to modulate the optical polarization and improve the LEE of DUV-LEDs, such as high-reflectivity metal contacts [18,19], distributed bragg reflector (DBR) structures [20–22], sapphire sidewall roughing [23–25], photonic crystal [26,27], nanorods DUV-LED structure [28,29], surface plasmon [30,31]. The omnidirectional reflector (ODR) structure has also been proved effective to help photons escape out of AlGaN-based DUV-LEDs [32–35]. Compared with other reflective structures such as metal and DBR, the ODR has wider stop band and higher reflectivity. According to the propagation path of DUV photons in the LED, those studies can be summarized by extracting photons from one of five emission zones to achieve the improved LEE, including surface emission zone, no escape zone, substrate edge emission zone, waveguide zone and p-GaN absorbing zone [6]. In addition, some reflective designs are hardly to be fabricated in reality. Their effects on LEE, especially for the chip-class TE and TM polarization, were only analyzed by analogue simulation computation.

Taking the above into consideration, the full-spatial omnidirectional reflector (FSODR) as a novel reflective strategy for analyzing the total angle characterization of optical polarization and the extraction behavior, has been introduced. The proposed FSODR DUV LED is based on flip-chip structure and simultaneously covered with ODR on the surface of n-AlGaN, the interface of p-GaN/p-AlGaN, and the sidewalls of Mesa and n-AlGaN/AlN layers. Moreover, it is attempted to build experimentally systematic research into the interaction of multiple zones’ reflection with the actual measurements of full-spatial TE/TM mode light. The research indicates that the FSODR structure has the TM synergy effect in extraction behavior and its LEE enhancement approximately 60% at a high current density of 140 A/cm2. The proposed FSODR model for the DUV LED application may open a new avenue for the design of the high efficient device with powerful LEE & WPE, and give a novel sight in the detailed feature inspection of optical polarization.

2. Materials and methods

2.1. Epitaxial growth of DUV-LED

The epitaxial growth of AlGaN-based DUV-LED was operated by metalorganic chemical vapor deposition (MOCVD). Trimethylaluminium, trimethylgallium, silane and ammonia were used as Al, Ga, Si and N sources, respectively. Hydrogen was used as the carrier gas. Firstly, a 2.5 um-thick AlN buffer layer was grown on (0001) sapphire substrate. Subsequently, a 2.5 um-thick Si-doped n-Al0.55Ga0.45N layer was grown as n-contact. The active region included seven periods of Al0.45Ga0.55N (3 nm)/Al0.55Ga0.45N (11 nm) multiple quantum wells (MQWs). Then, a ~25 nm-thick Mg-doping p-Al0.65Ga0.35N electron blocking layer (EBL) was grown, followed by a ~250nm thick Mg-doped p-Al0.5Ga0.5N layer. Finally, a ~50 nm thick Mg-doped p-GaN layer was served as the p-contact layer. The electron concentration and mobility of n-Al0.55Ga0.45N layer was 4 × 1018 cm−3 and 50 cm2/(V•s) respectively. The hole concentration and mobility of p-GaN layer was 4 × 1017 cm−3 and 10 cm2/(V•s) respectively. The data was confirmed by van der Pauw Hall measurement.

2.2. FSODR concept and samples design

For the conventional flip-chip DUV-LED, the photons could hardly escape from MQWs to sapphire substrate except the surface emission zone. It could be deduced that the surface area of n-AlGaN and the sidewall of Mesa, the interface of p-GaN/p-AlGaN, and the sidewall of n-AlGaN/AlN, are corresponded to the waveguide zone, the p-GaN absorptions zone and the substrate edge emission zone, respectively. All of the above parts were covered with ODR (SiO2/Al) for extraction of the TM- or TE-polarized DUV light as much as possible, which is defined as FSODR by us. An ODR consists of a low refractive index layer and a reflective metal with a complex refractive index. In this paper, SiO2 has low refractive index and acts as the dielectric layer. Al acts as the reflective metal, which has a high reflectance over 80% for the 280nm photons. Both SiO2 and Al are the commonly used materials in chip fabrication. This is the reason why we choose SiO2 and Al to form the FSODR. The three-dimensional exploded structure of the FSODR DUV-LED was schematically shown in Fig. 1(a). The FSODR composed of “FSODR-SiO2” and “FSODR-Al”. The thickness of SiO2 was 47 nm which was calculated by Fresnel equation mode [36–38]. The thickness of Al was 1200 nm to insure the formation of continuous reflective film and play the role of the thickening electrode. The reflectance spectrum of the designed ODR (SiO2/Al) in the UV wavelength range was shown in Fig. 1(b). The single part coating with ODR on the surface area of n-AlGaN, the interface of p-GaN/p-AlGaN, the sidewall of mesa and the sidewall of AlGaN/AlN were called n-ODR, p-ODR, Mesa-ODR and SW-ODR, respectively. In this study, the Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR, FSODR parallel six samples were all prepared for contrast research. The cross section diagrams for the various ODR structures were illustrated in Fig. 2.

 figure: Fig. 1

Fig. 1 (a) Schematic of the FSODR DUV-LED chip in three-dimensional exploded form. (b) The reflectance spectrum of the designed ODR (SiO2/Al) in the UV wavelength range.

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 figure: Fig. 2

Fig. 2 Schematic of the various ODR devices in cross-section view.

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2.3. Chip fabrication

Here, the chip size for each sample was 30 mil × 30 mil. The various samples were fabricated by the standard micro-fabrication processes of flip-chip DUV-LED with special mask designs. The detailed steps were described below. Firstly, the epitaxial wafer was etched to a depth of ~670 nm by inductively coupled plasma (ICP) using the BCl3/Cl2 etchant to form mesa geometry. Using the same technique, the sidewall of the AlGaN and AlN was etched by ~5 um depth. Similarly, the center of the p-GaN area was etched by ~100 nm to expose the interface of p-GaN/p-AlGaN. Secondly, the contact electrode of Ti/Al/Ti/Au (2/200/50/500 nm) for n-AlGaN layer was then deposited by electron beam evaporation (EBE), followed by the rapid thermal annealing at 800 °C for 45 s in N2 ambient. Thirdly, the FSODR-SiO2 of 47 nm thickness was made by Plasma Enhanced Chemical Vapor Deposition (PECVD). Then the area of FSODR-SiO2 above n-electrode was etched by the buffered hydrofluoride acid. The Al/Cr/Pt (1200/50/50 nm) was then deposited by EBE to act as FSODR-Al. Since the FSODR-Al was connected with the n-contact electrode, it could also play the role of the thickening electrode to insure the current spreading uniformly. Next, the Ni/Au (20/50 nm) as p-GaN contact electrode was deposited and post-annealed in an oxygen atmosphere at 500 °C for 5 min. The SiO2 of 500nm thickness was deposited and then etched at the p-GaN contact area. The Cr/Pt/Au/Cr (40/150/1000/40 nm) was deposited to connect the p-GaN contact electrodes. Finally, the SiO2 of 1000 nm thickness was deposited to act as the passive layer. After the contact holes were etched on the passive layer, the Cr/Al/Cr/Pt/Au (3/150/20/50/1000 nm) was deposited as NP-Pads. Besides the FSODR sample, other samples could also be understood by the Fig. 2 and the descriptions in this section. Notably, after preparing the Ni/Au contact layer, we deposited the SiO2 passivation layer for all samples before preparing the N-Pad and P-Pad. These identical layers between various samples are deliberately omitted in Fig. 2. All the reported samples have been screened with strict standard of reverse leakage current (<0.1uA@ −5V).

2.4. Performance characterizations

The prepared chip was bonded on an AlN ceramic substrate using solder paste for the performance characterization. The light output power (LOP), the current-voltage characteristic curve and the electroluminescence (EL) spectrum of the sample was measured by the ATA-1000 LED photoelectric analysis system with a 30-cm-diameter integrating sphere at room temperature. The self-built light-intensity test system composed of angle resolution bracket, Glan-Taylor prism and spectrometer, was used to obtain the degree of polarization (DOP) and TE/TM mode light-intensity distributions [39]. Notably, there is no direct relationship between LOP and TE/TM, since they are measured by different test systems and are based on different calculation principle. With the existing integrating sphere technology, the reflectivity of the inside wall for the DUV light is significantly lower than the visible light. In addition, the optical power of DUV-LED is just milliwatt level. So the TM with high-angle encounters more reflection times, which induces a serious dent. The LOP of DUV-LED is mainly responsible for the axial light with small angle range.

3. Results and discussion

3.1. Optical and electrical properties of FSODR sample

Figure 3(a) shows the light output power (LOP) as a function of injection current for the Reference and FSODR samples. The LOP of FSODR sample reaches 11.7 mW at injection current of 100 mA, which is 42% higher than that of the Reference sample. The injected current density of 100 mA is 77 A/cm2 which is commonly used in the industry. As the injection current increases, the LOP of FSODR and Reference samples gradually increases. But when the injection current is 180 mA (the injected current density of 140A/cm2),the LOP of Reference sample tends to saturate. The LOP of FSODR sample reaches 17.18 mW and is 60% higher than the Reference sample at the injection current of 180 mA. It is well known that the high LOP will lead to the relatively low junction temperature and cause the high saturation current density [40,41]. Figure 3(b) shows the LEE enhancement factor by means of the EQE of the FSODR sample divided by that of Reference sample. The LEE of FSODR sample approximately 1.4 times at injection current of 100 mA, as well as 1.6 times at injection current of 180 mA. The results indicate that the FSODR sample can greatly reflect the photons emitted by the MQWs to the sapphire surface, and significantly improve the LEE.

 figure: Fig. 3

Fig. 3 Optical and electric properties for the Reference and FSODR samples: (a) LOP, the inset showed a lighted FSODR DUV-LED device. (b) LEE enhancement factor, the inset showed the EQE characteristics. (c) Current-voltage characteristic, the inset showed the normalized EL spectra. (d) WPE characteristics.

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Figure 3(c) shows the current−voltage characteristics of the Reference and FSODR samples. The voltage of the FSODR sample is in turn 11.9% and 23.4% reduced than that of the reference sample at the injection current of 100 mA and 180 mA. Al based reflector in the FSODR sample not only acts as a reflective coating but also acts as a current spreading layer of n-AlGaN, which cause the lower voltage than the Reference sample [42,43]. The voltage and LOP work together on the wall plug efficiency (WPE), so the WPE is an important parameter describing the efficiency of LEDs. Figure 3(d) further reveals the relationship of WPE and injected current. The remarkable enhancement of WPE is approximately 61.2% in the FSODR sample than that of the Reference sample at injection current of 100 mA. And the enhancement of WPE reaches 97.6% at the injection current of 180 mA.

3.2. Optical polarization characteristics of FSODR sample

To further investigate the effect of FSODR sample on LEE, the optical polarization characteristics are actually measured. Since the optical polarization characteristics are symmetrical at 0° to 90° and −0° to −90°, the 0° to 90° is selected as the object of discussion in this work. The far-field distributions of the Reference and FSODR samples are shown in Fig. 4(a), which are based on the light intensity test system without the Glan-Taylor prism. According to the set of measurement system, each 9° of ϴ contains a measurement data. As can be seen, the spatial intensity of the FSODR sample is stronger than that of the Reference sample at any angle of ϴ. When the ϴ is near 36°, the spatial intensity of FSODR sample reaches the maximum value. It is quite coincidental that the critical angle at the sapphire/air interface is also around 34°, which means that the FSODR sample can strongly weaken the TIR compared to the Reference structure and improve the LEE. Figure 4(b) further shows the intensity increment of FSODR sample as a function of the ϴ from the Fig. 4(a). The intensity increment reaches the maximum value at ϴ of 45°. When the ϴ is 90°, the intensity increment reaches the minimum. Herein, all of intensity incremental values are positive at ϴ of (0°, 90°), which imply that the FSODR sample has enhancement effect on the TE and TM mode light.

 figure: Fig. 4

Fig. 4 Optical polarization characteristics of the Reference and FSODR samples: (a) Far-field distributions. (b) Normalized intensity increment of far-field distributions. (c) Full spatial TE/TM mode light intensity distributions. (d) Normalized intensity increment of full spatial TE mode light intensity distributions. (e) Normalized intensity increment of full spatial TM mode light intensity distributions.

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In order to go deep into the influence of FSODR sample on the TE/TM mode light enhancement, the full spatial TE/TM mode light intensity distributions of the Reference and FSODR samples are obtained by the test system with Glan-Taylor prism, and the results are shown in Fig. 4(c). The orientation and scale relation of TE/TM mode light radiated in the air ambient are illustrated in our pervious study [39]. As shown in Fig. 4(c), it is very obvious that the FSODR structure strongly helped to enhance the extraction of TE and TM mode light. The TE mode light intensity exists the maximum at ϴ of 27°, the TM mode light intensity exists the maximum at ϴ of 54°. Figures 4(d) and 4(e) further show the intensity increments of the TE and TM mode light, respectively. For the TE mode light, the intensity increment reaches the maximum at ϴ of 27°. The intensity increment is the minimum and zero at ϴ of 90°. All of intensity incremental values are positive at ϴ of (0°, 90°). For the TM mode light, the intensity increment reaches maximum at ϴ of 54°. The intensity increment is the minimum and zero at ϴ of 0°. All of intensity incremental values are positive at ϴ of (0°, 90°). It is worth noting that the incremental characteristic angles of ϴ for the TE and TM mode light are 27° and 54° respectively. The results show again that the FSODR sample does improve LEE by enhancing the TE and TM mode light. In addition, the DOP could be calculated to be 58.8% and 60% for DUV-LEDs with FSODR and Reference structures, respectively. It is well known that the TM mode light is extremely difficult to extract in DUV LEDs with high Al content [7,14]. However, the FSODR sample has a significant improvement effect on TM mode light, while the TE is also greatly enhanced, resulting in the similar values of DOP.

Theoretically, the FDTD method is used to simulate the cross section electric field profiles of TM- and TE -polarized light (shown in Fig. 5). For the TM- and TE-polarized light, the electric field amplitudes |E| inside the FSODR sample are much stronger than that inside the Reference sample. Especially, there are strong electric field distributions near the interfaces of AlN/sapphire and the sidewalls of AlN, AlGaN and mesa. As can be seen from the enlarged subgraph, the TM- and TE-polarized light in air ambient also exhibits significantly enhanced electric field distributions for the FSODR sample. The FDTD results prove that the FSODR can enhance the LEE by improving both TE- and TM-polarized light, which match well with the measured results in Fig. 4.

 figure: Fig. 5

Fig. 5 Cross-section distributions of electric field amplitude |E| at TE- and TM-polarized light simulated by 3D FDTD: (a)-(b) for the Reference sample. (c)-(d) for the FSODR sample

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3.3. Mechanism research with various division ODR structures

According to the concept and design, the FSODR is divided into four parts, which are named SW-ODR, Mesa-ODR, n-ODR, and p-ODR. Each part is taken out separately for research. To compare the parallel samples, we focus on the optical and electric properties at the injection current of 180 mA (shown in Fig. 6).

 figure: Fig. 6

Fig. 6 Comparison of optical and electric properties for all the samples, including Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR: (a) LOP and Voltage. (b) Enhancement factor of the LEE, voltage and WPE. (c) Reverse leakage current characteristics.

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Figure 6(a) shows that the LOPs of Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR samples are respectively 10.74 mW, 12.93 mW, 13.76mW, 15.28 mW, 16.72 mW and 17.18 mW, as well as the voltages are in turn 8.456 V, 7.556 V, 6.628 V, 6.764 V, 7.302 V, and 6.856 V. The values of the LOP, Voltage and WPE in Reference sample are acted as the base line, the enhancement factors for all the samples are displayed in Fig. 6(b). The LOP enhancement factors of the Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR samples increase in turn. The voltage enhancement factors of SW-ODR, Mesa-ODR, n-ODR and FSODR samples are smaller than that of the Reference sample, because of the uniform current spreading with coating the Al-based ODR [42,43]. The voltage and LOP work together on the WPE, so the WPE enhancement factors of the Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR samples improve in turn. Owing to the voltage of p-ODR sample is higher than the n-ODR sample, the WPE enhancement factors for the n-ODR and p-ODR samples are almost same. The reverse leakage current characteristics for various samples have been illustrated in Fig. 6(c). All the samples have very low reverse leakage current, which is lower than 0.1uA at the reverse bias of −5V. Moreover, all the samples have not been breakdown even at the high reverse bias of −25V.

The detailed increments of the far-field distributions and the full spatial TE/TM light intensity distributions are analyzed for each individual ODR sample (shown in Fig. 7). It is very interesting that all the samples with the feature extractions of optical polarization are completely different with each other, which is described as follows:

 figure: Fig. 7

Fig. 7 Optical polarization characteristics of the four division-ODR samples, including SW-ODR of (a)-(e), Mesa-ODR of (f)-(j), n-ODR of (k)-(o) and p-ODR of (p)-(f), comparing with the Reference sample.

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Figures 7(a)−7(e) displays the optical polarization characteristics of SW-ODR and Reference samples. As shown in Fig. 7(a), the spatial light intensity for the SW-ODR sample is slightly stronger than that of the Reference sample at ϴ (0°, 27°), and occurs the opposite trend at ϴ (27, 90°). Figure 7(b) further shows the intensity increment of SW-ODR sample as a function of the ϴ from the Fig. 7(a). The intensity increment reaches the maximum value at the ϴ of 0°, and the intensity increment reaches the minimum value at ϴ of 63°. When the ϴ is 27°, the intensity increment is zero. Hence, the ϴ can be divided into two zones, including ϴ (0°, 27°) for the positive intensity incremental value, and ϴ (27°, 90°) for the negative intensity incremental value. The results imply that the SW-ODR sample has enhancement effect, mainly on the TE mode light. The full spatial TE/TM mode light intensity distributions of the Reference and SW-ODR samples are shown in Fig. 7(c). It is obvious that the SW-ODR sample can enhance the TE mode light and weaken the TM mode light. For the TE mode light, the intensity increment is shown in Fig. 7(d). The intensity increment of TE mode light reaches the maximum value at ϴ of 0°, and reaches the minimum value at ϴ of 72°. When the ϴ is 63°, the intensity increment is zero. So the intensity increment is positive at ϴ (0°, 63°), and is negative at ϴ (63°, 90°). For the TM mode light (shown in Fig. 7(e)), the intensity increment exists the maximum value at ϴ of 27°, and the minimum value at ϴ of 72°. When the ϴ is ~42°, the intensity increment is zero. So the intensity increment is positive at ϴ (0°, 42°), and is negative at ϴ (42°, 90°). The results show that the SW-ODR sample can improve the TE mode light intensity and enhance LEE than Reference sample by effectively reflecting the light from AlGaN and AlN sidewalls to the sapphire surface.

Figures 7(f)−7(j) displays the optical polarization characteristics of Mesa-ODR and Reference samples. As shown in Fig. 7(f), it is found that the spatial light intensity for the Mesa-ODR sample is slightly stronger than that of the Reference sample at ϴ (0°, 30°), and occurs the opposite trend at ϴ (30, 90°). Figure 7(g) further shows the intensity increment of Mesa-ODR sample as a function of the ϴ from the Fig. 7(f). The intensity increment reaches the maximum value at ϴ of 0°, and the intensity increment reaches the minimum value at ϴ of 54°. When the ϴ is about 30°, the intensity increment is zero. Hence, the ϴ can be divided into two zones, including ϴ (0°, 30°) for the positive intensity incremental value, and ϴ (30°, 90°) for the negative intensity incremental value. The results imply that the Mesa-ODR sample has enhancement effect, mainly on the TE mode light. The full spatial TE/TM mode light intensity distributions of the Reference and Mesa-ODR samples are shown in Fig. 7(h). It is obvious that the Mesa-ODR sample can enhance the TE mode light and weaken the TM mode light. For the TE mode light, the intensity increment is shown in Fig. 7(i). The intensity increment of TE mode light reaches the maximum value at ϴ of 0°, and reaches the minimum value at ϴ of 45°. When the ϴ is about 30°, the intensity increment is zero. So the ϴ can be divided into two zones of (0°, 30°) and (30°, 90°), which corresponds to the intensity incremental value of positive and negative respectively. For the TM mode light (shown in Fig. 7(j)), the intensity increment exists the maximum value at ϴ of 18°, and the minimum value at ϴ of 54°. When the ϴ is 30°, the intensity increment is zero. And the intensity increment is positive at ϴ (0°, 30°), and is negative at ϴ (30°, 90°).

Figures 7(k)−7(o) displays the optical polarization characteristics of n-ODR and Reference samples. As shown in Fig. 7(k), the spatial intensity of the n-ODR sample is stronger than that of the Reference sample at any angle of ϴ. Figure 7(l) further shows the intensity increment of n-ODR sample as a function of the ϴ from the Fig. 7(k). The intensity increment reaches the maximum value at ϴ of 45°. When the ϴ is 90°, the intensity increment is the minimum and zero. So the all intensity incremental values are positive at ϴ of (0°, 90°), which implies that the n-ODR sample has enhancement effect on the TE and TM mode light. Figure 7(m) shows the full spatial TE/TM mode light intensity distributions of the Reference and n-ODR samples. Obviously, the n-ODR structure strongly helped to enhance the extraction of TE and TM mode light. The TE mode light intensity exists the maximum at ϴ of 18°, the TE mode light intensity exists the maximum at ϴ of 54°. Figures 7(n) and 7(o) further show the intensity increment of the TE and TM mode light, respectively. For the TE mode light, the intensity increment reaches the maximum at ϴ of 36°. The intensity increment is the minimum and zero at ϴ of 90°. All of TE intensity incremental values are positive at ϴ of (0°, 90°). For the TM mode light, the intensity increment reaches the maximum at ϴ of 54°. The intensity increment is the minimum and zero at ϴ of 0°. All of TM intensity incremental values are positive at ϴ of (0°, 90°). It is worth noting that the characteristic angles of ϴ for the TE and TM mode light are 36° and 54° respectively.

Figures 7(p)−7(t) indicates the optical polarization characteristics of p-ODR and Reference LEDs. As shown in Fig. 7(p), the spatial intensity of the p-ODR sample is stronger than that of the Reference sample at any angle of ϴ. Figure 7(q) further shows the intensity increment of p-ODR sample as a function of the ϴ from the Fig. 7(p). The intensity increment reaches the maximum value at ϴ of 18°. When the ϴ is 90°, the intensity increment is the minimum and zero. So the all intensity incremental values are positive at ϴ of (0°, 90°), which implies that the p-ODR sample has enhancement effect on the TE and TM mode light. Figure 7(r) shows the full spatial TE/TM mode light intensity distributions of the Reference and p-ODR samples. It is very obvious that the p-ODR structure strongly helped to enhance the extraction of TE and TM mode light. The TE mode light intensity exists the maximum at ϴ of 18°, the TE mode light intensity exists the maximum at ϴ of 54°. Figures 7(s) and 7(t) further show the intensity increment of the TE and TM mode light, respectively. For the TE mode light, the intensity increment reaches the maximum at ϴ of 18°. The intensity increment is the minimum and zero at ϴ of 90°. All of TE intensity incremental values are positive at ϴ of (0°, 90°). For the TM mode light, the intensity increment reaches the maximum at ϴ of 54°. The intensity increment is the minimum and zero at ϴ of 0°. All of TM intensity incremental values are positive at ϴ of (0°, 90°). Note that the characteristic angles of ϴ for the TE and TM mode light are 18° and 54° respectively.

In order to clearly summarize the feature extractions of different polarization intensity increment under various samples, Table 1 is presented. Each ODR sample has its unique polarization characteristics, including the value and range of ϴ.

Tables Icon

Table 1. Feature extractions of polarization intensity increment for various ODR samples

3.4. Synergy effect of FSODR for the TM mode light extraction

To further compare the differences in optical polarization characteristics between the four division ODR structures and the FSODR sample, the improvements of their total TE and TM mode light intensities to those of the Reference sample are calculated. The total TE and TM mode light intensities can be obtained by integrating the light intensities of full spatial TE/TM light intensity distributions from 0° to 90°. Then, we can compare the total TE/TM light intensity of any ODR sample with that of Reference sample to get the improvements. The improvements of total TE mode light intensities for the SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR samples are 7.6%, −0.4%, 20.9%, 57.9% and 73.1%, respectively. The improvements of total TM mode light intensities for the SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR samples are −5.4%, −19.9%, 23.7%, 40.5% and 79.8%, respectively. According to the synergetics, the total light increments of TE and TM modes in FSODR sample can be predicted to be 86% (the sum of 7.6%, −0.4%, 20.9% and 57.9%) and 38.9% (the sum of −5.4%, −19.9%, 23.7% and 40.5%). However, the real total light improvements of TE and TM modes in FSODR sample are 73.1% and 79.8% respectively. Interestingly, the real improvement of the total TM mode light is almost 2 times stronger than that of the expected value. The improvements of the samples for the total TM mode light intensity are shown in Fig. 8. Here, we propose a “TM Synergy Effect” on the total TM mode light of FSODR sample. Through the interaction and collaboration of the four division ODR structures, FSODR structure shows a much stronger improvement of total TM mode light intensity. The ‘TM Synergy Effect’ can be concluded that the FSODR can extract the TM light, which lose in a single ODR structure, into the air ambient as much as possible. For example, in the Mesa-ODR sample, the photons reflected back by the reflector are also lost by the TIR of the n-AlGaN waveguide region or absorbed by p-GaN. If n-ODR or p-ODR structure exists meanwhile, the lost TM light can be truly utilized and extracted to air ambient. This ‘TM Synergy Effect’ further demonstrates that the one part of the ODR structure is not enough to extract the light most effectively. Only by considering multiple zones of ODR structure together, the “Synergy Effect” can be utilized to the best effect.

 figure: Fig. 8

Fig. 8 Comparison of the enhanced total TM intensities for all the samples.

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4. Conclusion

Through the FSODR and its four separated ODRs, this paper has revealed the relationship between full-spatial reflection system, optical polarization characterization and light extraction behavior at the chip level. We have shown that the interaction of multiple zones’ reflection of the DUV LED chip is very meaningful in modulating the light propagation paths and inducing the strong improvement of TE and TM mode light extraction. Furthermore, the different spatial of ODR structure can be integratedly used to modulate unique optical polarization characteristics. Finally, the “TM synergistic effect” for tremendous enhancement of TM mode light is significant because the emission for DUV-LEDs is predominantly TM polarized, which is extremely difficult to be extracted.

Funding

Key Project of Chinese National Development Programs (2018YFB0406602); Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences (IIMDKFJJ-17-09); National Natural Science Foundation of China (11574166, 61377034, 61774065); China Postdoctoral Science Foundation (2019M652632).

Acknowledgments

The authors are grateful to the Center for Nanoscale Characterization & Devices (CNCD) of WNLO and the center of Micro-Fabrication and Characterization (CMFC) OF WNLO for the support in measurements. Thanks to Shenghai Xu engineer for the support in chip fabrication.

Disclosures

The authors declare no conflicts of interest.

References

1. A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008). [CrossRef]  

2. D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018). [CrossRef]  

3. M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019). [CrossRef]  

4. W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010). [CrossRef]  

5. F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014). [CrossRef]  

6. M. Kneissl, J. Rass, III-Nitride Ultraviolet Emitters Technology and Applications, Springer Series in Materials Science, volume 227 (Springer, 2016).

7. K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004). [CrossRef]  

8. I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003). [CrossRef]  

9. S. Fan, Z. Qin, C. He, X. Wang, B. Shen, and G. Zhang, “Strain effect on the optical polarization properties of c-plane Al0.26Ga0.74N/GaN superlattices,” Opt. Express 22(6), 6322–6328 (2014). [CrossRef]   [PubMed]  

10. J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012). [CrossRef]  

11. T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011). [CrossRef]  

12. W. Wang, H. Lu, L. Fu, C. He, M. Wang, N. Tang, F. Xu, T. Yu, W. Ge, and B. Shen, “Enhancement of optical polarization degree of AlGaN quantum wells by using staggered structure,” Opt. Express 24(16), 18176–18183 (2016). [CrossRef]   [PubMed]  

13. M. Hou, Z. Qin, C. He, J. Cai, X. Wang, and B. Shen, “Effect of injection current on the optical polarization of AlGaN-based ultraviolet light-emitting diodes,” Opt. Express 22(16), 19589–19594 (2014). [CrossRef]   [PubMed]  

14. C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015). [CrossRef]  

15. H. Long, S. Wang, J. Dai, F. Wu, J. Zhang, J. Chen, R. Liang, Z. C. Feng, and C. Chen, “Internal strain induced significant enhancement of deep ultraviolet light extraction efficiency for AlGaN multiple quantum wells grown by MOCVD,” Opt. Express 26(2), 680–686 (2018). [CrossRef]   [PubMed]  

16. X. Chen, C. Ji, Y. Xiang, X. Kang, B. Shen, and T. Yu, “Angular distribution of polarized light and its effect on light extraction efficiency in AlGaN deep-ultraviolet light-emitting diodes,” Opt. Express 24(10), A935–A942 (2016). [CrossRef]   [PubMed]  

17. H. Wang, L. Fu, H. M. Lu, X. N. Kang, J. J. Wu, F. J. Xu, and T. J. Yu, “Anisotropic dependence of light extraction behavior on propagation path in AlGaN-based deep-ultraviolet light-emitting diodes,” Opt. Express 27(8), A436–A444 (2019). [CrossRef]   [PubMed]  

18. T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017). [CrossRef]  

19. S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018). [CrossRef]  

20. S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019). [CrossRef]   [PubMed]  

21. M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018). [CrossRef]  

22. M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018). [CrossRef]  

23. K. H. Lee, H. J. Park, S. H. Kim, M. Asadirad, Y. T. Moon, J. S. Kwak, and J. H. Ryou, “Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes,” Opt. Express 23(16), 20340–20349 (2015). [CrossRef]   [PubMed]  

24. Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017). [CrossRef]   [PubMed]  

25. B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019). [CrossRef]   [PubMed]  

26. S. I. Inoue, T. Naoki, T. Kinoshita, T. Obata, and H. Yanagi, “Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure,” Appl. Phys. Lett. 106(13), 131104 (2015). [CrossRef]  

27. S. I. Inoue, N. Tamari, and M. Taniguchi, “150 mW deep-ultraviolet light-emitting diodes with large-area AlN nanophotonic light-extraction structure emitting at 265 nm,” Appl. Phys. Lett. 110(14), 141106 (2017). [CrossRef]  

28. M. Djavid and Z. T. Mi, “Enhancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures,” Appl. Phys. Lett. 108(5), 051102 (2016). [CrossRef]  

29. S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017). [CrossRef]   [PubMed]  

30. N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012). [CrossRef]   [PubMed]  

31. K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015). [CrossRef]   [PubMed]  

32. N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010). [CrossRef]  

33. D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015). [CrossRef]  

34. J. J. Wierer Jr., A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014). [CrossRef]  

35. A. I. Zhmakin, “Enhancement of light extraction from light emitting diodes,” Phys. Rep. 498(4–5), 189–241 (2011). [CrossRef]  

36. Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003). [CrossRef]  

37. J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006). [CrossRef]  

38. J. Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, T. Gessmann, and E. F. Schubert, “Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material,” Opt. Lett. 30(12), 1518–1520 (2005). [CrossRef]   [PubMed]  

39. S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018). [CrossRef]   [PubMed]  

40. D. Lu and C. P. Wong, Materials for Advanced Packaging (Springer, 2009).

41. Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005). [CrossRef]  

42. H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000). [CrossRef]  

43. X. Guo and E. F. Schubert, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates,” Appl. Phys. Lett. 78(21), 3337–3339 (2001). [CrossRef]  

References

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  • |

  1. A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
    [Crossref]
  2. D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018).
    [Crossref]
  3. M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019).
    [Crossref]
  4. W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
    [Crossref]
  5. F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
    [Crossref]
  6. M. Kneissl, J. Rass, III-Nitride Ultraviolet Emitters Technology and Applications, Springer Series in Materials Science, volume 227 (Springer, 2016).
  7. K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004).
    [Crossref]
  8. I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003).
    [Crossref]
  9. S. Fan, Z. Qin, C. He, X. Wang, B. Shen, and G. Zhang, “Strain effect on the optical polarization properties of c-plane Al0.26Ga0.74N/GaN superlattices,” Opt. Express 22(6), 6322–6328 (2014).
    [Crossref] [PubMed]
  10. J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
    [Crossref]
  11. T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
    [Crossref]
  12. W. Wang, H. Lu, L. Fu, C. He, M. Wang, N. Tang, F. Xu, T. Yu, W. Ge, and B. Shen, “Enhancement of optical polarization degree of AlGaN quantum wells by using staggered structure,” Opt. Express 24(16), 18176–18183 (2016).
    [Crossref] [PubMed]
  13. M. Hou, Z. Qin, C. He, J. Cai, X. Wang, and B. Shen, “Effect of injection current on the optical polarization of AlGaN-based ultraviolet light-emitting diodes,” Opt. Express 22(16), 19589–19594 (2014).
    [Crossref] [PubMed]
  14. C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
    [Crossref]
  15. H. Long, S. Wang, J. Dai, F. Wu, J. Zhang, J. Chen, R. Liang, Z. C. Feng, and C. Chen, “Internal strain induced significant enhancement of deep ultraviolet light extraction efficiency for AlGaN multiple quantum wells grown by MOCVD,” Opt. Express 26(2), 680–686 (2018).
    [Crossref] [PubMed]
  16. X. Chen, C. Ji, Y. Xiang, X. Kang, B. Shen, and T. Yu, “Angular distribution of polarized light and its effect on light extraction efficiency in AlGaN deep-ultraviolet light-emitting diodes,” Opt. Express 24(10), A935–A942 (2016).
    [Crossref] [PubMed]
  17. H. Wang, L. Fu, H. M. Lu, X. N. Kang, J. J. Wu, F. J. Xu, and T. J. Yu, “Anisotropic dependence of light extraction behavior on propagation path in AlGaN-based deep-ultraviolet light-emitting diodes,” Opt. Express 27(8), A436–A444 (2019).
    [Crossref] [PubMed]
  18. T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
    [Crossref]
  19. S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
    [Crossref]
  20. S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019).
    [Crossref] [PubMed]
  21. M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
    [Crossref]
  22. M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
    [Crossref]
  23. K. H. Lee, H. J. Park, S. H. Kim, M. Asadirad, Y. T. Moon, J. S. Kwak, and J. H. Ryou, “Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes,” Opt. Express 23(16), 20340–20349 (2015).
    [Crossref] [PubMed]
  24. Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
    [Crossref] [PubMed]
  25. B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
    [Crossref] [PubMed]
  26. S. I. Inoue, T. Naoki, T. Kinoshita, T. Obata, and H. Yanagi, “Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure,” Appl. Phys. Lett. 106(13), 131104 (2015).
    [Crossref]
  27. S. I. Inoue, N. Tamari, and M. Taniguchi, “150 mW deep-ultraviolet light-emitting diodes with large-area AlN nanophotonic light-extraction structure emitting at 265 nm,” Appl. Phys. Lett. 110(14), 141106 (2017).
    [Crossref]
  28. M. Djavid and Z. T. Mi, “Enhancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures,” Appl. Phys. Lett. 108(5), 051102 (2016).
    [Crossref]
  29. S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
    [Crossref] [PubMed]
  30. N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
    [Crossref] [PubMed]
  31. K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
    [Crossref] [PubMed]
  32. N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
    [Crossref]
  33. D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
    [Crossref]
  34. J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
    [Crossref]
  35. A. I. Zhmakin, “Enhancement of light extraction from light emitting diodes,” Phys. Rep. 498(4–5), 189–241 (2011).
    [Crossref]
  36. Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
    [Crossref]
  37. J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
    [Crossref]
  38. J. Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, T. Gessmann, and E. F. Schubert, “Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material,” Opt. Lett. 30(12), 1518–1520 (2005).
    [Crossref] [PubMed]
  39. S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
    [Crossref] [PubMed]
  40. D. Lu and C. P. Wong, Materials for Advanced Packaging (Springer, 2009).
  41. Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
    [Crossref]
  42. H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
    [Crossref]
  43. X. Guo and E. F. Schubert, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates,” Appl. Phys. Lett. 78(21), 3337–3339 (2001).
    [Crossref]

2019 (4)

M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019).
[Crossref]

H. Wang, L. Fu, H. M. Lu, X. N. Kang, J. J. Wu, F. J. Xu, and T. J. Yu, “Anisotropic dependence of light extraction behavior on propagation path in AlGaN-based deep-ultraviolet light-emitting diodes,” Opt. Express 27(8), A436–A444 (2019).
[Crossref] [PubMed]

S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019).
[Crossref] [PubMed]

B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
[Crossref] [PubMed]

2018 (6)

M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
[Crossref]

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
[Crossref]

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

H. Long, S. Wang, J. Dai, F. Wu, J. Zhang, J. Chen, R. Liang, Z. C. Feng, and C. Chen, “Internal strain induced significant enhancement of deep ultraviolet light extraction efficiency for AlGaN multiple quantum wells grown by MOCVD,” Opt. Express 26(2), 680–686 (2018).
[Crossref] [PubMed]

D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018).
[Crossref]

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

2017 (4)

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
[Crossref]

S. I. Inoue, N. Tamari, and M. Taniguchi, “150 mW deep-ultraviolet light-emitting diodes with large-area AlN nanophotonic light-extraction structure emitting at 265 nm,” Appl. Phys. Lett. 110(14), 141106 (2017).
[Crossref]

S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
[Crossref] [PubMed]

2016 (3)

2015 (5)

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

S. I. Inoue, T. Naoki, T. Kinoshita, T. Obata, and H. Yanagi, “Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure,” Appl. Phys. Lett. 106(13), 131104 (2015).
[Crossref]

K. H. Lee, H. J. Park, S. H. Kim, M. Asadirad, Y. T. Moon, J. S. Kwak, and J. H. Ryou, “Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes,” Opt. Express 23(16), 20340–20349 (2015).
[Crossref] [PubMed]

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

2014 (4)

J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
[Crossref]

M. Hou, Z. Qin, C. He, J. Cai, X. Wang, and B. Shen, “Effect of injection current on the optical polarization of AlGaN-based ultraviolet light-emitting diodes,” Opt. Express 22(16), 19589–19594 (2014).
[Crossref] [PubMed]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

S. Fan, Z. Qin, C. He, X. Wang, B. Shen, and G. Zhang, “Strain effect on the optical polarization properties of c-plane Al0.26Ga0.74N/GaN superlattices,” Opt. Express 22(6), 6322–6328 (2014).
[Crossref] [PubMed]

2012 (2)

J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
[Crossref]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

2011 (2)

A. I. Zhmakin, “Enhancement of light extraction from light emitting diodes,” Phys. Rep. 498(4–5), 189–241 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

2010 (2)

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

2008 (1)

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

2006 (1)

J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
[Crossref]

2005 (2)

J. Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, T. Gessmann, and E. F. Schubert, “Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material,” Opt. Lett. 30(12), 1518–1520 (2005).
[Crossref] [PubMed]

Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
[Crossref]

2004 (1)

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004).
[Crossref]

2003 (2)

I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003).
[Crossref]

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

2001 (1)

X. Guo and E. F. Schubert, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates,” Appl. Phys. Lett. 78(21), 3337–3339 (2001).
[Crossref]

2000 (1)

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Ahmed, F.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Alatawi, A. A.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
[Crossref]

Alias, M. S.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
[Crossref]

Allerman, A. A.

J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
[Crossref]

Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
[Crossref]

Amano, H.

M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019).
[Crossref]

Asadirad, M.

Ashry, I.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
[Crossref]

Balakrishnan, K.

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

Bhat, J. C.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Bilenko, Y.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

Cai, J.

Chen, C.

Chen, C. Q.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Chen, J.

Chen, J. W.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Chen, X.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

X. Chen, C. Ji, Y. Xiang, X. Kang, B. Shen, and T. Yu, “Angular distribution of polarized light and its effect on light extraction efficiency in AlGaN deep-ultraviolet light-emitting diodes,” Opt. Express 24(10), A935–A942 (2016).
[Crossref] [PubMed]

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

Chen, Z.

Cho, J.

J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
[Crossref]

Cho, W.

Chua, C.

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

Chua, C. L.

J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
[Crossref]

Dai, J.

Dai, J. N.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Deng, J.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

Ding, X. H.

M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
[Crossref]

Djavid, M.

M. Djavid and Z. T. Mi, “Enhancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures,” Appl. Phys. Lett. 108(5), 051102 (2016).
[Crossref]

Einfeldt, S.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Fan, S.

Feneberg, M.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

Feng, Z. C.

Fu, L.

Gao, N.

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

Gao, Y. L.

M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
[Crossref]

Gaska, R.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

Ge, W.

Gessmann, T.

J. Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, T. Gessmann, and E. F. Schubert, “Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material,” Opt. Lett. 30(12), 1518–1520 (2005).
[Crossref] [PubMed]

Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
[Crossref]

Gill, W. N.

Goldhahn, R.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

Gui, C.

B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
[Crossref] [PubMed]

Guo, C. L.

D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018).
[Crossref]

Guo, X.

X. Guo and E. F. Schubert, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates,” Appl. Phys. Lett. 78(21), 3337–3339 (2001).
[Crossref]

Guo, Y. A.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

Guttmann, M.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

Han, J.

M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019).
[Crossref]

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

He, C.

Hirayama, H.

T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
[Crossref]

Holguin-Lerma, J. A.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
[Crossref]

Hoppe, M.

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Hou, M.

Hou, M. J.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

Hu, J. H.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Hu, X.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

Huang, K.

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

Huh, C.

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Hwang, H.

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Hwang, S.

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

Inoue, S. I.

S. I. Inoue, N. Tamari, and M. Taniguchi, “150 mW deep-ultraviolet light-emitting diodes with large-area AlN nanophotonic light-extraction structure emitting at 265 nm,” Appl. Phys. Lett. 110(14), 141106 (2017).
[Crossref]

S. I. Inoue, T. Naoki, T. Kinoshita, T. Obata, and H. Yanagi, “Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure,” Appl. Phys. Lett. 106(13), 131104 (2015).
[Crossref]

Ji, C.

Jiang, H. X.

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004).
[Crossref]

Jiang, K.

D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018).
[Crossref]

Johnson, N. M.

J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

Kang, J.

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

Kang, N. W.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Kang, X.

Kang, X. N.

Katona, T.

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

Khan, A.

A. Khan, K. Balakrishnan, and T. Katona, “Ultraviolet light-emitting diodes based on group three nitrides,” Nat. Photonics 2(2), 77–84 (2008).
[Crossref]

Kim, A. Y.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Kim, D. J.

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Kim, D. Y.

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

Kim, H.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Kim, J.

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

Kim, J. K.

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
[Crossref]

Kim, K. K.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Kim, S. H.

Kim, S. J.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Kim, S. W.

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Kinoshita, T.

S. I. Inoue, T. Naoki, T. Kinoshita, T. Obata, and H. Yanagi, “Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure,” Appl. Phys. Lett. 106(13), 131104 (2015).
[Crossref]

Knauer, A.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Kneissl, M.

M. Kneissl, T. Y. Seong, J. Han, and H. Amano, “The emergence and prospects of deep-ultraviolet light-emitting diode technologies,” Nat. Photonics 13(4), 233–244 (2019).
[Crossref]

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Kolbe, T.

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

J. E. Northrup, C. L. Chua, Z. Yang, T. Wunderer, M. Kneissl, N. M. Johnson, and T. Kolbe, “Effect of strain and barrier composition on the polarization of light emission from AlGaN/AlN quantum wells,” Appl. Phys. Lett. 100(2), 021101 (2012).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

Krames, M. R.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Kueller, V.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

Kuhn, C.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

Kuo, H. C.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Kwak, J. S.

Kwon, J. S.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Lapeyrade, M.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

Lee, H. J.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Lee, J. M.

H. Kim, J. M. Lee, C. Huh, S. W. Kim, D. J. Kim, S. J. Park, and H. Hwang, “Modeling of a GaN-based light-emitting diode for uniform current spreading,” Appl. Phys. Lett. 77(12), 1903 (2000).
[Crossref]

Lee, J. W.

D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
[Crossref]

Lee, K. H.

Lee, K. J.

S. Oh, K. J. Lee, H. J. Lee, S. J. Kim, J. Han, N. W. Kang, J. S. Kwon, H. Kim, K. K. Kim, and S. J. Park, “Periodic air-nanoplate-embedded AlGaN/air/Al omnidirectional reflector for high efficiency ultraviolet emitters,” Scr. Mater. 146(15), 41–45 (2018).
[Crossref]

Li, D. B.

D. B. Li, K. Jiang, X. J. Sun, and C. L. Guo, “AlGaN photonics: recent advances in materials and ultraviolet devices,” Adv. Opt. Photonics 10(1), 43–110 (2018).
[Crossref]

Li, J.

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004).
[Crossref]

Li, J. M.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

Li, N.

B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
[Crossref] [PubMed]

Li, S.

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
[Crossref] [PubMed]

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

Liang, R.

Lin, J. Y.

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang, “Unique optical properties of AlGaN alloys and related ultraviolet emitters,” Appl. Phys. Lett. 84(25), 5264–5266 (2004).
[Crossref]

Liu, L.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
[Crossref] [PubMed]

Liu, M. L.

M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
[Crossref]

Liu, S.

Liu, X.

S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019).
[Crossref] [PubMed]

S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
[Crossref] [PubMed]

Liu, X. T.

M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
[Crossref]

Liu, Y.

B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
[Crossref] [PubMed]

S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019).
[Crossref] [PubMed]

Lobo, N.

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Long, H.

Long, H. L.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
[Crossref] [PubMed]

Lu, H.

Lu, H. M.

Ludowise, M. J.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Lunev, A.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. S. Shur, and R. Gaska, “Efficiency droop in 245–247 nm AlGaN light-emitting diodes with continuous wave 2 mW output power,” Appl. Phys. Lett. 96(6), 061102 (2010).
[Crossref]

Luo, H.

J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
[Crossref]

Martin, P. S.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Mehnke, F.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

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I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003).
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S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
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M. Djavid and Z. T. Mi, “Enhancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures,” Appl. Phys. Lett. 108(5), 051102 (2016).
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T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
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Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
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J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
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Moseley, M. W.

J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
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Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
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Ooi, B. S.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
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Park, J. H.

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Priante, D.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
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C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
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Sadaf, S. M.

S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
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T. Takano, T. Mino, J. Sakai, N. Noguchi, K. Tsubaki, and H. Hirayama, “Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency,” Appl. Phys. Express 10(3), 031002 (2017).
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D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
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J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
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J. Q. Xi, M. Ojha, W. Cho, J. L. Plawsky, W. N. Gill, T. Gessmann, and E. F. Schubert, “Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material,” Opt. Lett. 30(12), 1518–1520 (2005).
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Shen, Y. C.

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
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D. Y. Kim, J. H. Park, J. W. Lee, S. Hwang, S. J. Oh, J. Kim, C. Sone, E. F. Schubert, and J. K. Kim, “Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission,” Light Sci. Appl. 4(4), e263 (2015).
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J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
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M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
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M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
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Tangi, M.

M. S. Alias, M. Tangi, J. A. Holguin-Lerma, E. Stegenburgs, A. A. Alatawi, I. Ashry, R. C. Subedi, D. Priante, M. K. Shakfa, T. K. Ng, and B. S. Ooi, “Review of nanophotonics approaches using nanostructures and nanofabrication for III-nitrides ultraviolet-photonic devices,” J. Nanophotonics 12, 043508 (2018).
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S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
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T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
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I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003).
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B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
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Wang, J. X.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
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Wang, S.

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[Crossref] [PubMed]

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Wang, X.

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C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

Weyers, M.

C. Reich, M. Guttmann, M. Feneberg, T. Wernicke, F. Mehnke, C. Kuhn, J. Rass, M. Lapeyrade, S. Einfeldt, A. Knauer, V. Kueller, M. Weyers, R. Goldhahn, and M. Kneissl, “Strongly transverse-electric-polarized emission from deep ultraviolet AlGaN quantum well light emitting diodes,” Appl. Phys. Lett. 107(14), 142101 (2015).
[Crossref]

F. Mehnke, C. Kuhn, M. Guttmann, C. Reich, T. Kolbe, V. Kueller, A. Knauer, M. Lapeyrade, S. Einfeldt, J. Rass, T. Wernicke, M. Weyers, and M. Kneissl, “Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 105(5), 051113 (2014).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
[Crossref]

N. Lobo, H. Rodriguez, A. Knauer, M. Hoppe, S. Einfeldt, P. Vogt, M. Weyers, and M. Kneissl, “Enhancement of light extraction in ultraviolet light-emitting diodes using nanopixel contact design with Al reflector,” Appl. Phys. Lett. 96(8), 081109 (2010).
[Crossref]

Wierer, J. J.

J. J. Wierer, A. A. Allerman, I. Montano, and M. W. Moseley, “Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes,” Appl. Phys. Lett. 105(6), 061106 (2014).
[Crossref]

Y. C. Shen, J. J. Wierer, M. R. Krames, M. J. Ludowise, M. S. Misra, F. Ahmed, A. Y. Kim, G. O. Mueller, J. C. Bhat, S. A. Stockman, and P. S. Martin, “Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes,” Appl. Phys. Lett. 82(14), 2221–2223 (2003).
[Crossref]

Wu, F.

Wu, J. J.

Wu, Y.

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J. K. Kim, J. Q. Xi, H. Luo, E. F. Schubert, J. Cho, C. Sone, and Y. Park, “Enhanced light-extraction in GaInN near-ultraviolet light-emitting diode with Al-based omnidirectional reflector having NiZn/AgNiZn/Ag microcontacts,” Appl. Phys. Lett. 89(14), 141123 (2006).
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Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
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Xiang, Y.

Xie, H. Z.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
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Xu, F. J.

Xu, L. L.

S. Wang, J. N. Dai, J. H. Hu, S. Zhang, L. L. Xu, H. L. Long, J. W. Chen, Q. X. Wan, H. C. Kuo, and C. Q. Chen, “Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure,” ACS Photonics 5(9), 3534–3540 (2018).
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Yan, H.

Yan, J. C.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
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T. Kolbe, A. Knauer, C. Chua, Z. Yang, V. Kueller, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Temperature dependence of the field emission from the few-layer graphene film,” Appl. Phys. Lett. 99(16), 163103 (2011).
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Zhang, Y.

Y. A. Guo, Y. Zhang, J. C. Yan, H. Z. Xie, L. Liu, X. Chen, M. J. Hou, Z. X. Qin, J. X. Wang, and J. M. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
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A. I. Zhmakin, “Enhancement of light extraction from light emitting diodes,” Phys. Rep. 498(4–5), 189–241 (2011).
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B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
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M. L. Liu, S. J. Zhou, X. T. Liu, Y. L. Gao, and X. H. Ding, “Comparative experimental and simulation studies of high-power AlGaN-based 353nm ultraviolet flip-chip and top-emitting LEDs,” Jpn. J. Appl. Phys. 57(3), 031001 (2018).
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[Crossref]

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[Crossref]

Y. Xi, J. Q. Xi, T. Gessmann, J. M. Shah, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. 86(3), 031907 (2005).
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S. M. Sadaf, S. Zhao, Y. Wu, Y. H. Ra, X. Liu, S. Vanka, and Z. Mi, “An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band,” Nano Lett. 17(2), 1212–1218 (2017).
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Nanomaterials (Basel) (1)

B. Tang, J. Miao, Y. Liu, H. Wan, N. Li, S. Zhou, and C. Gui, “Enhanced light extraction of flip-chip mini-LEDs with prism-structured sidewall,” Nanomaterials (Basel) 9(3), 319 (2019).
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Opt. Express (8)

W. Wang, H. Lu, L. Fu, C. He, M. Wang, N. Tang, F. Xu, T. Yu, W. Ge, and B. Shen, “Enhancement of optical polarization degree of AlGaN quantum wells by using staggered structure,” Opt. Express 24(16), 18176–18183 (2016).
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H. Wang, L. Fu, H. M. Lu, X. N. Kang, J. J. Wu, F. J. Xu, and T. J. Yu, “Anisotropic dependence of light extraction behavior on propagation path in AlGaN-based deep-ultraviolet light-emitting diodes,” Opt. Express 27(8), A436–A444 (2019).
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S. Zhou, X. Liu, H. Yan, Z. Chen, Y. Liu, and S. Liu, “Highly efficient GaN-based high-power flip-chip light-emitting diodes,” Opt. Express 27(12), A669–A692 (2019).
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K. H. Lee, H. J. Park, S. H. Kim, M. Asadirad, Y. T. Moon, J. S. Kwak, and J. H. Ryou, “Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes,” Opt. Express 23(16), 20340–20349 (2015).
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Opt. Lett. (1)

Phys. Rep. (1)

A. I. Zhmakin, “Enhancement of light extraction from light emitting diodes,” Phys. Rep. 498(4–5), 189–241 (2011).
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Sci. Rep. (2)

N. Gao, K. Huang, J. Li, S. Li, X. Yang, and J. Kang, “Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells,” Sci. Rep. 2(1), 816 (2012).
[Crossref] [PubMed]

K. Huang, N. Gao, C. Wang, X. Chen, J. Li, S. Li, X. Yang, and J. Kang, “Top- and bottom-emission-enhanced electroluminescence of deep-UV light-emitting diodes induced by localised surface plasmons,” Sci. Rep. 4(1), 4380 (2015).
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Scr. Mater. (1)

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M. Kneissl, J. Rass, III-Nitride Ultraviolet Emitters Technology and Applications, Springer Series in Materials Science, volume 227 (Springer, 2016).

D. Lu and C. P. Wong, Materials for Advanced Packaging (Springer, 2009).

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Figures (8)

Fig. 1
Fig. 1 (a) Schematic of the FSODR DUV-LED chip in three-dimensional exploded form. (b) The reflectance spectrum of the designed ODR (SiO2/Al) in the UV wavelength range.
Fig. 2
Fig. 2 Schematic of the various ODR devices in cross-section view.
Fig. 3
Fig. 3 Optical and electric properties for the Reference and FSODR samples: (a) LOP, the inset showed a lighted FSODR DUV-LED device. (b) LEE enhancement factor, the inset showed the EQE characteristics. (c) Current-voltage characteristic, the inset showed the normalized EL spectra. (d) WPE characteristics.
Fig. 4
Fig. 4 Optical polarization characteristics of the Reference and FSODR samples: (a) Far-field distributions. (b) Normalized intensity increment of far-field distributions. (c) Full spatial TE/TM mode light intensity distributions. (d) Normalized intensity increment of full spatial TE mode light intensity distributions. (e) Normalized intensity increment of full spatial TM mode light intensity distributions.
Fig. 5
Fig. 5 Cross-section distributions of electric field amplitude | E | at TE- and TM-polarized light simulated by 3D FDTD: (a)-(b) for the Reference sample. (c)-(d) for the FSODR sample
Fig. 6
Fig. 6 Comparison of optical and electric properties for all the samples, including Reference, SW-ODR, Mesa-ODR, n-ODR, p-ODR and FSODR: (a) LOP and Voltage. (b) Enhancement factor of the LEE, voltage and WPE. (c) Reverse leakage current characteristics.
Fig. 7
Fig. 7 Optical polarization characteristics of the four division-ODR samples, including SW-ODR of (a)-(e), Mesa-ODR of (f)-(j), n-ODR of (k)-(o) and p-ODR of (p)-(f), comparing with the Reference sample.
Fig. 8
Fig. 8 Comparison of the enhanced total TM intensities for all the samples.

Tables (1)

Tables Icon

Table 1 Feature extractions of polarization intensity increment for various ODR samples

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