Abstract

The anisotropic extraction dependence of polarized light on propagation path in AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) is investigated by simulations and photoluminescence (PL) measurements. Theoretical calculations based on kp approximation and Monte Carol ray tracing indicate that there are two kinds of polarized sources with different angular distributions in ~280 nm AlGaN-based LEDs, s-polarized (spherical-shaped) and p-polarized (dumbbell-shaped) sources, which have different extraction behaviors. It is found that the total light extraction intensities are improved with decreasing the propagation path, and the lateral surface extraction gradually becomes dominant. Moreover, the extraction intensity of s-polarized light improves more than that of p-polarized light when the propagation path decreases, leading to a greater polarization degree. Polarization-resolved PL measurements show that the polarization degree of extracted light from lateral facet of the AlGaN multiple quantum well sample can be enhanced from 1% to 17% as the average propagation path reduces by 0.6 mm, which is consistent with the simulation results of the anisotropic dependence of light extraction on propagation path. Our results are significant for understanding and modulating the anisotropic 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 diode (LED) has attracted much attention due to its wide range of potential applications, such as water purification, sterilization and high-density optical data storage [1,2]. However, compared to visible range LEDs, the AlGaN-based LEDs have still been limited in commercial applications because of their low external quantum efficiency (EQE), especially for the emission wavelength (λ) < 300 nm [3–9]. Improving the crystalline quality of AlGaN grown on sapphire substrate, hole concentration in p-AlGaN layer and hole injection efficiency related to the EQE are urgent problems to be solved [10,11]. Moreover, the optical polarization characteristics of AlGaN-based active layer determine the emission patterns and play an important role in the light extraction efficiency (LEE) of DUV LEDs, which makes a major contribution to EQE [12–15]. Previous investigations report that the polarization of emission light switches from transverse-electric (TE) mode (electric vector, E⊥c) to transverse-magnetic (TM) mode (E∥c) when the Al composition of AlGaN quantum wells (QWs) increases [16–20]. In contrast to TE mode, TM mode light predominantly propagates along lateral direction and undergoes strong total internal reflection (TIR), which is more difficult to extract from LEDs [21].

Generally, the anisotropic optical polarization is considered to be determined by the valence band structure of AlGaN QWs. In order to enhance the proportion of TE mode emission, many simulations and experiments have been carried out to modulate polarized sources by designing the structure of AlGaN active region [22,23]. For example, using compressive strain, narrow quantum well layers, barriers with high aluminum mole fractions or AlN-deta-GaN QW structures, dominant TE-polarized light can be obtained [18,19,24–26]. In addition to the polarized source determined by QW band structures, the propagation process is also an important factor that should not be ignored, which greatly affects the extraction behavior of polarized light from LEDs. It has been experimentally indicated that using the narrow mesa stripe structures exposing more sidewall of active region, better extraction of the sidewall-emitting TM-polarized DUV light can be obtained, leading to a remarkable enhancement in LEDs’ LEE [27]. The main reason has been considered as shorter average propagation path for the DUV photons prior to being extracted that reduces the probability of re-absorption loss [27,28]. To the best of our knowledge, however, the propagation path effect closely related to the extraction behavior of polarized light has not been clearly identified. It is necessary to investigate the relationship between anisotropic extraction behavior and propagation path, and find out how polarized sources extract from DUV LEDs.

In this paper, a systematic investigation of propagation path impact on anisotropic extraction behavior in AlGaN-based DUV LEDs is carried out by using kp approximation, Monte Carol ray tracing technique and polarization-resolved photoluminescence (PL) measurements. Based on kp approximation, s- and p-polarizations are derived to describe polarization properties of emitted light from active region. The propagation process of angularly distributed sources is simulated by Monte Carol ray tracing technique. We have analyzed detailed extraction behaviors of s- and p-polarized light from ~280 nm AlGaN-based LEDs with different chip sizes and their contributions to the polarization degree. It is found that the total light extraction intensities are improved with decreasing the propagation path, and the lateral surface extraction becomes dominant. Moreover, the extraction intensity of s-polarized light improves more than that of p-polarized light as the propagation path decreases, which results in a greater polarization degree. Polarization-resolved PL measurements confirm that the polarization degree of extracted light from lateral facet of the AlGaN multiple quantum well (MQW) sample can be enhanced from 1% to 17% when the average propagation path reduces by 0.6 mm. Our results enlighten that not only the properties of polarized sources but also their anisotropic extraction dependences on propagation path give great influence on the light extraction efficiency. By changing paths of light propagation, we can modulate the light extraction behaviors so as to improve the efficiency of DUV LEDs.

2. Theoretical model

To investigate the effect of propagation path on the extraction behavior of polarized light, we first derive the angular distribution of polarized sources in QWs. Based on kp perturbation method [29–31], TE- and TM-polarized spontaneous emission rates (rspTE(ω)andrspTM(ω)) of c-oriented AlGaN MQWs can be calculated. The AlGaN related parameters are taken from linear combinations of AlN and GaN components in [32]. It is noted that the light ray along a particular direction includes both TE and TM modes. Therefore we use s and p oscillating components to describe the optical polarization of propagated light [33,34], the direction of which is illustrated by azimuthal angle φ and zenith angle θ shown in Fig. 1(a). The electric field of the s-component (-sinφ, cosφ, 0) is perpendicular to the plane determined by the emitting direction of the ray and the c-axis, while p-component (-cosθcosφ, -cosθsinφ, sinθ) oscillates in this plane and vertically to the electric field of s. In particular, when θ=90°, s- and p-components just correspond to the TE and TM modes, respectively. Under hexagonal symmetry and biaxial stress hypothesis, the relation of spontaneous emission rates can be expressed as [34],

 figure: Fig. 1

Fig. 1 (a) Schematic diagrams of coordinate system in simulation and measurement. The two oscillating components (s and p) are illustrated. Angular distributions of (b) s-polarized, (c) cos2θ p-polarized and (d) sin2θ p-polarized sources.

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spolarization:rsps(ω)=rspTE(ω),
ppolarization:rspp(ω)=rspTE(ω)cos2θ+rspTM(ω)sin2θ.

It is clearly found that the spontaneous emission’s spatially angular dependence separates from the energy dependence. Thus there are three kinds of polarized sources with different angular distributions, named as s-polarized, cos2θ p-polarized and sin2θ p-polarized sources, which are shown in Figs. 1(b)-1(d). Moreover, the contributions of these angularly distributed sources are determined by the energy dependences rspTE(ω) and rspTM(ω).

When the polarized sources from active region including s and p oscillating components are obtained, the propagation path impact on light extraction behavior for the AlGaN-based DUV LEDs can be further analyzed by Monte Carol ray tracing technique. The light extraction process including refraction, reflection and absorption, which affects the final angularly polarized intensity, is considered in tracing a million of light rays based on Fresnel’s law [35,36]. In the simulation model of the LED structure, MQWs are regarded as a source layer composed of a set of grid points emitting s- or p-polarized rays. The refractive indices of AlGaN, AlN and sapphire are set as 2.6, 2.2 and 1.8, respectively [36–38]. Moreover, the absorption coefficients of MQW and n-AlGaN layer are assumed to be 1000 and 10 cm−1, respectively [39].

3. Results and discussion

The simulated model is simplified typical ~280 nm AlGaN DUV LED structure shown in Fig. 2(a). The p-GaN contact layer is not included here to eliminate its absorption and highlight the effect of propagation path. In order to investigate the propagation path impact on anisotropic extraction behavior, we select two chips of different sizes (0.1 mm × 0.1 mm and 1 mm × 1 mm) for simulation. Based on kp method, we obtain rspTE(ω)rspTM(ω) in ~280 nm AlGaN QWs [34], i.e., the contribution of sin2θ p-polarized source is much smaller and can be neglected in this system. Hence, in the following simulation, only s-polarized and cos2θ p-polarized sources are considered.

 figure: Fig. 2

Fig. 2 (a) Simplified LED structure and the two chips of different sizes (1 mm × 1 mm and 0.1 mm × 0.1 mm). (b) Simulated total light extraction intensity for s- and p-polarizations as a function of θ. S- and p-polarized extraction intensities from top surface, lateral surface and bottom surface for 1 mm × 1 mm (c) and 0.1 mm × 0.1 mm (d) chips in simulation.

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The angular-dependent total light extraction intensities (φ=90°, θ from 0° to 180°) for s- and p-polarizations from all sides of the LEDs with different chip sizes are shown in Fig. 2(b). The light sources used in the simulations for the 1 mm × 1 mm and 0.1 mm × 0.1 mm chips are the combination of s-polarized and cos2θ p-polarized sources. Here we assume that both intensities and numbers of isolated sources are the same in these two chips, and the spacing of dot-shaped light rays is different. The extracted intensities at φ=90° are just given here because light intensities are repeated when φ changes by 90° for the symmetry of square geometry and the variation trends of light intensities with θ are similar when φ changes within 90°. The thick sapphire substrate (80 μm in thickness) with large lateral area favors light extraction. Also, the refractive index of sapphire (1.8) is smaller than that of AlGaN (2.6) resulting in less internal reflection. As a result, there is more light extracted from the sapphire side (θ>90°) than the AlGaN side (θ<90°). As shown in Fig. 2(b), for the smaller chip of 0.1 mm × 0.1 mm, the s-polarized extraction intensities are obviously greater than that of 1 mm × 1 mm size. However, the p-polarized intensities for the two chips with different sizes are similar, especially at θ=90°. This will contribute to a greater polarization degree (ρ) defined as ρ=(sp)/(s+p) for smaller chip.

To further analyze the light extraction behavior, we calculate the light extraction intensity from top surface, lateral surface and bottom surface for 1 mm × 1 mm and 0.1 mm × 0.1 mm chips as given in Figs. 2(c) and 2(d), respectively. It can be seen that the intensities of s- and p-polarized light from the top and bottom surfaces are similar for the LEDs with different chip sizes. As to the lateral surface, however, a substantial increase of the s-polarized light is revealed when the chip size becomes smaller and the extracted light from lateral surface gradually becomes dominant. Therefore, the enhancement of total s-polarized intensity is attributed to more extracted light for s-polarization from lateral surface of the LED with smaller chip size. It is obvious that as the chip size of LED increases, the average propagation path of light becomes longer. All the aforementioned simulation results clearly indicate that the propagation path greatly affects the extraction behavior of s- and p-polarized light, which is an important factor related to the extraction efficiency. It is found that the total light extraction intensity of s-polarized component improves more than that of p-polarized component as the propagation path decreases, leading to greater polarization degree.

In order to elucidate the origin of different extraction behaviors for s- and p-polarized sources, we further investigate the extraction behavior of light with different emission angles. Figure 3(a) shows the sketch map based on simulation results for the extraction path of four light rays with typical emission angles (l1,  l2,l3 and l4). The l1 and l4 represent the rays in the extraction cone which can easily extract from top or bottom surface. The light ray l2, which undergoes strong TIR, should be more difficult to extract with increasing the chip size. For l3 in the lateral extraction cone, the proportion of extracted light becomes smaller due to the absorption loss caused by longer propagation path. We have simulated light extraction efficiency as a function of the emission angle (θE) for 0.1 mm × 0.1 mm and 1 mm × 1 mm chips by using Monte Carol ray tracing technique in Fig. 3(b). This method is only applicable when the geometric dimensions of LEDs are much larger than the emission wavelength. The light rays of sources are all in a particular direction when the θE is determined. It is demonstrated that the critical angle of total reflection here is about 23°. As a result, there is high and same extraction efficiency for two chips with different sizes when the emission angle θE<23° or θE>157°. It is only the light with the emission angle from 23° to 157° (23°<θE<157°) whose extraction efficiency strongly relies on the propagation path. As the propagation path decreases, the extraction efficiency shows an obvious enhancement. Such propagation-path-sensitive light can be simply represented as the shadow part in the profile of s-polarized and cos2θ p-polarized sources shown in Fig. 3(c). For the s-polarized source with isotropic spherical-shaped distribution, the propagation-path-sensitive light is much more than that for cos2θ p-polarized source. Therefore, when the average in-plane propagation path decreases, the total extraction intensity of s-polarized light improves more than that of p-polarized light, which results in a greater polarization degree.

 figure: Fig. 3

Fig. 3 (a) Sketch for the extraction path of four typical light rays with different emission angles (l1,  l2, l3 and l4). (b) The simulated extraction efficiency as a function of the emission angle (θE) for 0.1 mm × 0.1 mm and 1 mm × 1 mm chips, respectively. (c) The propagation-path-sensitive light is represented as the shadow part in the profile of s-polarized and cos2θ p-polarized sources.

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To directly investigate the effect of propagation path in experiment, we adopt polarization-resolved PL setup as shown in Fig. 4. Such configuration is able to not only control the same emission area but also obtain the variation of the propagation path simply by changing the distance of the laser spot center from the edge of the sample. The optical polarization characteristics of the fabricated AlGaN MQW sample with the same structure as the simulated one are measured. The MQWs are grown on sapphire substrates with 3 × 2″ close-coupled-showerhead (CCS) Aixtron metal organic chemical vapor deposition (MOCVD) system. Deposition begins with a 2.2 μm thick AlN layer, followed by a 20 period AlN/AlGaN superlattice layer and a 2 μm thick Si-doped Al0.55Ga0.45N layer. The Si doping concentration is 2 × 1018 cm−3 for the n-AlGaN film. Next, 10 period MQWs are grown consisting of well and barrier layers of Al0.37Ga0.63N and Al0.55Ga0.45N, respectively. The width of each quantum barrier is 10 nm and quantum well is 2.3 nm. Finally, the structure is completed with a 25 nm thick Al0.55Ga0.45N cap layer. PL measurements are performed using a 4th harmonic of Q-switched YAG:Nd laser with λ = 266 nm. The polarization degree is measured by excitation on the top surface of the c-plane wafer and detection from the lateral facet (θ=90°), where s- and p-polarized light just correspond respectively to the TE- and TM-polarizations. The size of the sample is 6 mm × 6 mm, and the diameter of the laser spot is 0.3 mm. As the laser spot center moves away from the sample edge, the propagation path becomes longer, and then the effect of propagation path can be evaluated by the change of polarization properties. We have measured the polarization degree with a distance interval of 0.1 mm by moving laser spot on the surface of sample.

 figure: Fig. 4

Fig. 4 Schematic diagram of the polarization-resolved PL measurement setup. The observed TE- and TM-polarized light from lateral facet (θ=90°) just correspond respectively to the s- and p-polarizations obtained in the simulation results.

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The PL results and corresponding polarization degree as a function of the average in-plane propagation path (x¯) are shown in Fig. 5(a). Insets are TE- and TM-polarized PL spectra for x¯=0.15mm and x¯=0.75mm, respectively. Both TE- and TM-polarized PL intensities show an improvement with decreasing the propagation path. As the in-plane propagation path increases, the polarization degree of light extraction from lateral facet is gradually reduced. It is worthwhile to note that the degree of polarization is enhanced from 1% to 17% when x¯ reduces by 0.6 mm. Our experimental results directly confirm the anisotropic extraction dependence of polarized light on propagation path. On the other hand, the total light extraction intensities of s- and p-polarizations at θ=90° for a series of chips with different sizes are simulated. The calculated degree of polarization is summarized in Fig. 5(b). The polarization degree becomes larger with decreasing the propagation path because the extraction intensity of s-polarized light improves more than that of p-polarized light. There is a negative correlation between the polarization degree and in-plane propagation path, which exhibits great agreement with the experimental results. It is suggested that the light extraction intensity can be significantly improved by modulating the anisotropic extraction behavior of polarized light through the variation of propagation path.

 figure: Fig. 5

Fig. 5 Measured (a) and simulated (b) polarization degree of extracted light from lateral facet of the AlGaN MQW sample as a function of the average in-plane propagation path (x¯). Insets are TE- and TM-polarized PL spectra for x¯=0.15mm and x¯=0.75mm, respectively.

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4. Conclusion

In summary, the anisotropic dependence of light extraction behavior on propagation path in AlGaN-based DUV LEDs has been investigated by simulations as well as polarization-resolved PL measurements. Based on kp approximation and Monte Carol ray tracing technique, we find there are two kinds of polarized sources with different angular distributions (s-polarized and cos2θ p-polarized sources) in ~280 nm AlGaN-based LEDs. The propagation path is an important factor related to the extraction behavior of polarized light. As the propagation path decreases, the total light extraction intensities are improved, and the lateral surface extraction gradually becomes dominant. Moreover, the extraction intensity of s-polarized light improves more than that of p-polarized light with decreasing the propagation path, leading to a greater polarization degree. The polarization degree of extracted light from lateral facet of the AlGaN MQW sample can be enhanced from 1% to 17% when the average propagation path reduces by 0.6 mm. Our results are helpful to modulate the anisotropic extraction behavior of polarized sources, which provides a new way to design high efficiency AlGaN-based DUV LEDs.

Funding

National Key Research and Development Program of China (2016YFB0400802); National Natural Science Foundation of China (61774008, 61674007); Beijing Municipal Science and Technology Project (Z181100004418008).

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References

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  1. H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
    [Crossref]
  2. Y. Muramoto, M. Kimura, and S. Nouda, “Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp,” Semicond. Sci. Technol. 29(8), 084004 (2014).
    [Crossref]
  3. G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
    [Crossref]
  4. A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
    [Crossref]
  5. H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
    [Crossref]
  6. M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
    [Crossref]
  7. 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]
  8. F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
    [Crossref]
  9. W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]
  10. L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
    [Crossref] [PubMed]
  11. C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
    [Crossref]
  12. J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
    [Crossref]
  13. Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. Li, “Light extraction enhancement of AlGaN-based ultraviolet light-emitting diodes by substrate sidewall roughening,” Appl. Phys. Lett. 111(1), 011102 (2017).
    [Crossref] [PubMed]
  14. Y. K. Ooi and J. Zhang, “Light extraction efficiency analysis of flip-chip ultraviolet light-emitting diodes with patterned sapphire substrate,” IEEE Photonics J. 10(4), 8200913 (2018).
    [Crossref]
  15. S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]
  16. H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
    [Crossref]
  17. T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
    [Crossref]
  18. 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]
  19. T. M. Al tahtamouni, J. Y. Lin, and H. X. Jiang, “Optical polarization in c-plane Al-rich AlN/AlxGa1-xN single quantum wells,” Appl. Phys. Lett. 101(4), 042103 (2012).
    [Crossref]
  20. S.-H. Park and J.-I. Shim, “Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures,” Appl. Phys. Lett. 102(22), 221109 (2013).
    [Crossref]
  21. 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]
  22. C. Y. Su, M. C. Tsai, K. P. Chou, H. C. Chiang, H. H. Lin, M. Y. Su, Y. R. Wu, Y. W. Kiang, and C. C. Yang, “Method for enhancing the favored transverse-electric-polarized emission of an AlGaN deep-ultraviolet quantum well,” Opt. Express 25(22), 26365–26377 (2017).
    [Crossref] [PubMed]
  23. 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]
  24. 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]
  25. C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
    [Crossref]
  26. C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
    [Crossref]
  27. 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]
  28. J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
    [Crossref]
  29. S. L. Chuang and C. S. Chang, “k,” Phys. Rev. B Condens. Matter 54(4), 2491–2504 (1996).
    [Crossref] [PubMed]
  30. S. L. Chuang, “Optical gain of strained wurtzite GaN quantum-well lasers,” IEEE J. Quantum Electron. 32(10), 1791–1800 (1996).
    [Crossref]
  31. X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
    [Crossref]
  32. I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94(6), 3675–3696 (2003).
    [Crossref]
  33. G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
    [Crossref]
  34. 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]
  35. F. Hu, K.-Y. Qian, and Y. Luo, “Far-field pattern simulation of flip-chip bonded power light-emitting diodes by a Monte Carlo photon-tracing method,” Appl. Opt. 44(14), 2768–2771 (2005).
    [Crossref] [PubMed]
  36. Z. Liu, K. Wang, X. Luo, and S. Liu, “Precise optical modeling of blue light-emitting diodes by Monte Carlo ray-tracing,” Opt. Express 18(9), 9398–9412 (2010).
    [Crossref] [PubMed]
  37. K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
    [Crossref]
  38. G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
    [Crossref]
  39. 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]

2018 (6)

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

Y. K. Ooi and J. Zhang, “Light extraction efficiency analysis of flip-chip ultraviolet light-emitting diodes with patterned sapphire substrate,” IEEE Photonics J. 10(4), 8200913 (2018).
[Crossref]

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

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]

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

2017 (3)

C. Y. Su, M. C. Tsai, K. P. Chou, H. C. Chiang, H. H. Lin, M. Y. Su, Y. R. Wu, Y. W. Kiang, and C. C. Yang, “Method for enhancing the favored transverse-electric-polarized emission of an AlGaN deep-ultraviolet quantum well,” Opt. Express 25(22), 26365–26377 (2017).
[Crossref] [PubMed]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

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

2016 (2)

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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]

2015 (5)

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]

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]

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (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]

2014 (5)

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[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]

H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
[Crossref]

Y. Muramoto, M. Kimura, and S. Nouda, “Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp,” Semicond. Sci. Technol. 29(8), 084004 (2014).
[Crossref]

J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
[Crossref]

2013 (2)

S.-H. Park and J.-I. Shim, “Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures,” Appl. Phys. Lett. 102(22), 221109 (2013).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

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]

T. M. Al tahtamouni, J. Y. Lin, and H. X. Jiang, “Optical polarization in c-plane Al-rich AlN/AlxGa1-xN single quantum wells,” Appl. Phys. Lett. 101(4), 042103 (2012).
[Crossref]

2011 (1)

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

2010 (5)

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Z. Liu, K. Wang, X. Luo, and S. Liu, “Precise optical modeling of blue light-emitting diodes by Monte Carlo ray-tracing,” Opt. Express 18(9), 9398–9412 (2010).
[Crossref] [PubMed]

K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
[Crossref]

2007 (1)

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
[Crossref]

2006 (1)

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

2005 (1)

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 (1)

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

1997 (1)

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

1996 (2)

S. L. Chuang and C. S. Chang, “k,” Phys. Rev. B Condens. Matter 54(4), 2491–2504 (1996).
[Crossref] [PubMed]

S. L. Chuang, “Optical gain of strained wurtzite GaN quantum-well lasers,” IEEE J. Quantum Electron. 32(10), 1791–1800 (1996).
[Crossref]

Adachi, S.

K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
[Crossref]

Al tahtamouni, T. M.

T. M. Al tahtamouni, J. Y. Lin, and H. X. Jiang, “Optical polarization in c-plane Al-rich AlN/AlxGa1-xN single quantum wells,” Appl. Phys. Lett. 101(4), 042103 (2012).
[Crossref]

Allerman, A. A.

J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
[Crossref]

Asadirad, M.

Bilenko, Y.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

Chang, C. S.

S. L. Chuang and C. S. Chang, “k,” Phys. Rev. B Condens. Matter 54(4), 2491–2504 (1996).
[Crossref] [PubMed]

Chen, C.

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]

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Chen, J.

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

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]

Chen, X.

Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. 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]

Chen, X. J.

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Chen, Z.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

Chen, Z. Z.

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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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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).
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H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
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Hou, M.

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Hu, F.

Hu, J.

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[Crossref]

Hu, X.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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).
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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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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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

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H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
[Crossref]

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
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Kang, X. N.

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Kim, D. Y.

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[Crossref]

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.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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, S. H.

Kim, Y.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
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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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Kneissl, M.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Kolbe, T.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

Kuhn, C.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[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]

Kuo, H.-C.

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Kwak, J. S.

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]

Ledentsov, N.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

Lee, J.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

Lee, J. W.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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.

Li, J.

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

Liang, R.

Lin, H. H.

Lin, J. Y.

T. M. Al tahtamouni, J. Y. Lin, and H. X. Jiang, “Optical polarization in c-plane Al-rich AlN/AlxGa1-xN single quantum wells,” Appl. Phys. Lett. 101(4), 042103 (2012).
[Crossref]

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, C.

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

Liu, L.

Y. Guo, Y. Zhang, J. Yan, H. Xie, L. Liu, X. Chen, M. Hou, Z. Qin, J. Wang, and J. 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, N.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

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Liu, Z.

Lobo, N.

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

Lobo-Ploch, N.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

Long, H.

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

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).
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G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Lunev, A.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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, X.

Luo, Y.

Maeda, N.

H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
[Crossref]

Mehnke, F.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[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).
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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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A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
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J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
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Mukai, T.

A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
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Muramoto, Y.

Y. Muramoto, M. Kimura, and S. Nouda, “Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp,” Semicond. Sci. Technol. 29(8), 084004 (2014).
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Murayama, T.

A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
[Crossref]

Nakarmi, M. L.

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]

Nam, K. B.

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]

Narukawa, Y.

A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
[Crossref]

Niikura, E.

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

Noguchi, N.

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
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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).
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Y. Muramoto, M. Kimura, and S. Nouda, “Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp,” Semicond. Sci. Technol. 29(8), 084004 (2014).
[Crossref]

Nukui, T.

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

Oh, S. 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]

Ohashi, T.

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
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K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
[Crossref]

Ooi, Y. K.

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

Y. K. Ooi and J. Zhang, “Light extraction efficiency analysis of flip-chip ultraviolet light-emitting diodes with patterned sapphire substrate,” IEEE Photonics J. 10(4), 8200913 (2018).
[Crossref]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

Park, H. J.

Park, J. H.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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]

Park, S.-H.

S.-H. Park and J.-I. Shim, “Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures,” Appl. Phys. Lett. 102(22), 221109 (2013).
[Crossref]

Park, Y.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

Pristovsek, M.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

Qian, K.-Y.

Qin, Z.

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

Rass, J.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[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]

Reich, C.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[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]

Rodriguez, H.

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

Rothe, M.-A.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

Ryou, J. H.

Schubert, E. F.

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

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]

Senuma, M.

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

Shatalov, M.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

Shen, B.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

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]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Shim, J.-I.

S.-H. Park and J.-I. Shim, “Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures,” Appl. Phys. Lett. 102(22), 221109 (2013).
[Crossref]

Shur, M.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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).
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Soga, T.

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
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Sone, C.

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]

Song, W.

Stellmach, J.

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

Su, C. Y.

Su, M. Y.

Sun, W.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

Takeuchi, K.

K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
[Crossref]

Toyoda, S.

H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
[Crossref]

Tsai, M. C.

Umeno, M.

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

Verma, J.

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

Vogt, P.

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Vurgaftman, I.

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

Wan, Q.

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Wang, G.

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

Wang, J.

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

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

Wang, K.

Wang, S.

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]

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Watanabe, J.

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

Wernicke, T.

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, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Wierer, J. J.

J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
[Crossref]

Wu, F.

Wu, H.

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

Wu, J. J.

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

Wu, Y. R.

Wunderer, T.

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]

Xiang, Y.

Xie, H.

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

Xing, H.

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

Xu, L.

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Yamamoto, M.

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

Yan, J.

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

Yang, C. C.

Yang, G. F.

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

Yang, J.

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

Yang, Z.

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]

M. Kneissl, T. Kolbe, C. Chua, V. Kueller, N. Lobo, J. Stellmach, A. Knauer, H. Rodriguez, S. Einfeldt, Z. Yang, N. M. Johnson, and M. Weyers, “Advances in group III-nitride-based deep UV light-emitting diode technology,” Semicond. Sci. Technol. 26(1), 014036 (2011).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[Crossref]

Yatabe, T.

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
[Crossref]

Yu, G.

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

Yu, T.

Yu, T. J.

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Yuan, G. C.

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Zhang, G. Y.

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

Zhang, J.

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]

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

Y. K. Ooi and J. Zhang, “Light extraction efficiency analysis of flip-chip ultraviolet light-emitting diodes with patterned sapphire substrate,” IEEE Photonics J. 10(4), 8200913 (2018).
[Crossref]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

Zhang, K.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

Zhang, Q.

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

Zhang, R.

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

Zhang, S.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

Zhang, Y.

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

Zhao, W.

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

L. He, W. Zhao, K. Zhang, C. He, H. Wu, N. Liu, W. Song, Z. Chen, and S. Li, “Performance enhancement of AlGaN-based 365 nm ultraviolet light-emitting diodes with a band-engineering last quantum barrier,” Opt. Lett. 43(3), 515–518 (2018).
[Crossref] [PubMed]

Zheng, Y. D.

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

ACS Photonics (2)

S. Wang, J. Dai, J. Hu, S. Zhang, L. Xu, H. Long, J. Chen, Q. Wan, H.-C. Kuo, and C. 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]

J. W. Lee, J. H. Park, D. Y. Kim, E. F. Schubert, J. Kim, J. Lee, Y. Kim, Y. Park, and J. K. Kim, “Arrays of truncated cone AlGaN deep-ultraviolet light-emitting diodes facilitating efficient outcoupling of in-plane emission,” ACS Photonics 3(11), 2030–2034 (2016).
[Crossref]

Appl. Opt. (1)

Appl. Phys. Express (1)

A. Fujioka, T. Misaki, T. Murayama, Y. Narukawa, and T. Mukai, “Improvement in output power of 280-nm deep ultraviolet light-emitting diode by using AlGaN multi quantum wells,” Appl. Phys. Express 3(4), 041001 (2010).
[Crossref]

Appl. Phys. Lett. (15)

H. Hirayama, T. Yatabe, N. Noguchi, T. Ohashi, and N. Kamata, “231–261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire,” Appl. Phys. Lett. 91(7), 071901 (2007).
[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]

W. Sun, M. Shatalov, J. Deng, X. Hu, J. Yang, A. Lunev, Y. Bilenko, M. 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]

H. Kawanishi, M. Senuma, M. Yamamoto, E. Niikura, and T. Nukui, “Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region,” Appl. Phys. Lett. 89(8), 081121 (2006).
[Crossref]

T. Kolbe, A. Knauer, C. Chua, Z. Yang, S. Einfeldt, P. Vogt, N. M. Johnson, M. Weyers, and M. Kneissl, “Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes,” Appl. Phys. Lett. 97(17), 171105 (2010).
[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. M. Al tahtamouni, J. Y. Lin, and H. X. Jiang, “Optical polarization in c-plane Al-rich AlN/AlxGa1-xN single quantum wells,” Appl. Phys. Lett. 101(4), 042103 (2012).
[Crossref]

S.-H. Park and J.-I. Shim, “Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures,” Appl. Phys. Lett. 102(22), 221109 (2013).
[Crossref]

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]

X. J. Chen, T. J. Yu, H. M. Lu, G. C. Yuan, B. Shen, and G. Y. Zhang, “Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap,” Appl. Phys. Lett. 103(18), 181117 (2013).
[Crossref]

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

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]

C. Liu, Y. K. Ooi, S. M. Islam, J. Verma, H. Xing, D. Jena, and J. Zhang, “Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes,” Appl. Phys. Lett. 110(7), 071103 (2017).
[Crossref]

C. Liu, Y. K. Ooi, S. M. Islam, H. Xing, D. Jena, and J. Zhang, “234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes,” Appl. Phys. Lett. 112(1), 011101 (2018).
[Crossref]

G. Yu, G. Wang, H. Ishikawa, M. Umeno, T. Soga, T. Egawa, J. Watanabe, and T. Jimbo, “Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method,” Appl. Phys. Lett. 70(24), 3209–3211 (1997).
[Crossref]

Cryst. Growth Des. (1)

C. He, W. Zhao, H. Wu, S. Zhang, K. Zhang, L. He, N. Liu, Z. Chen, and B. Shen, “High-quality AlN film grown on sputtered AlN/sapphire via growth-mode modification,” Cryst. Growth Des. 18(11), 6816–6823 (2018).
[Crossref]

IEEE J. Quantum Electron. (1)

S. L. Chuang, “Optical gain of strained wurtzite GaN quantum-well lasers,” IEEE J. Quantum Electron. 32(10), 1791–1800 (1996).
[Crossref]

IEEE Photonics J. (2)

G. F. Yang, Q. Zhang, J. Wang, S. M. Gao, R. Zhang, and Y. D. Zheng, “Analysis of 270/290/330-nm AlGaN-based deep ultraviolet light-emitting diodes with different Al content in quantum wells and barriers,” IEEE Photonics J. 7(6), 2200707 (2015).
[Crossref]

Y. K. Ooi and J. Zhang, “Light extraction efficiency analysis of flip-chip ultraviolet light-emitting diodes with patterned sapphire substrate,” IEEE Photonics J. 10(4), 8200913 (2018).
[Crossref]

J. Appl. Phys. (5)

J. J. Wierer, I. Montaño, M. H. Crawford, and A. A. Allerman, “Effect of thickness and carrier density on the optical polarization of Al0.44Ga0.56N/Al0.55Ga0.45N quantum well layers,” J. Appl. Phys. 115(17), 174501 (2014).
[Crossref]

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

G. C. Yuan, X. J. Chen, T. J. Yu, H. M. Lu, Z. Z. Chen, X. N. Kang, J. J. Wu, and G. Y. Zhang, “Angular distribution of polarized spontaneous emissions and its effect on light extraction behavior in InGaN-based light emitting diodes,” J. Appl. Phys. 115(9), 093106 (2014).
[Crossref]

F. Mehnke, C. Kuhn, J. Stellmach, T. Kolbe, N. Lobo-Ploch, J. Rass, M.-A. Rothe, C. Reich, N. Ledentsov, M. Pristovsek, T. Wernicke, and M. Kneissl, “Effect of heterostructure design on carrier injection and emission characteristics of 295 nm light emitting diodes,” J. Appl. Phys. 117(19), 195704 (2015).
[Crossref]

K. Takeuchi, S. Adachi, and K. Ohtsuka, “Optical properties of AlxGa1−xN alloy,” J. Appl. Phys. 107(2), 023306 (2010).
[Crossref]

Jpn. J. Appl. Phys. (1)

H. Hirayama, N. Maeda, S. Fujikawa, S. Toyoda, and N. Kamata, “Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes,” Jpn. J. Appl. Phys. 53(10), 100209 (2014).
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Figures (5)

Fig. 1
Fig. 1 (a) Schematic diagrams of coordinate system in simulation and measurement. The two oscillating components (s and p) are illustrated. Angular distributions of (b) s-polarized, (c) cos2θ p-polarized and (d) sin2θ p-polarized sources.
Fig. 2
Fig. 2 (a) Simplified LED structure and the two chips of different sizes (1 mm × 1 mm and 0.1 mm × 0.1 mm). (b) Simulated total light extraction intensity for s- and p-polarizations as a function of θ. S- and p-polarized extraction intensities from top surface, lateral surface and bottom surface for 1 mm × 1 mm (c) and 0.1 mm × 0.1 mm (d) chips in simulation.
Fig. 3
Fig. 3 (a) Sketch for the extraction path of four typical light rays with different emission angles ( l 1 ,     l 2 , l 3 and l 4 ). (b) The simulated extraction efficiency as a function of the emission angle (θE) for 0.1 mm × 0.1 mm and 1 mm × 1 mm chips, respectively. (c) The propagation-path-sensitive light is represented as the shadow part in the profile of s-polarized and cos2θ p-polarized sources.
Fig. 4
Fig. 4 Schematic diagram of the polarization-resolved PL measurement setup. The observed TE- and TM-polarized light from lateral facet ( θ = 90 ° ) just correspond respectively to the s- and p-polarizations obtained in the simulation results.
Fig. 5
Fig. 5 Measured (a) and simulated (b) polarization degree of extracted light from lateral facet of the AlGaN MQW sample as a function of the average in-plane propagation path ( x ¯ ). Insets are TE- and TM-polarized PL spectra for x ¯ = 0.15 mm and x ¯ = 0.75 mm , respectively.

Equations (2)

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s polarization : r s p s ( ω ) = r s p T E ( ω ) ,
p polarization : r s p p ( ω ) = r s p T E ( ω ) cos 2 θ + r s p T M ( ω ) sin 2 θ .

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