Abstract

The growth of a two-section, core-shell, InGaN/GaN quantum-well (QW) nanorod- (NR-) array light-emitting diode device based on a pulsed growth technique with metalorganic chemical vapor deposition is demonstrated. A two-section n-GaN NR is grown through a tapering process for forming two uniform NR sections of different cross-sectional sizes. The cathodoluminescence (CL), photoluminescence (PL), and electrolumines-cence (EL) characterization results of the two-section NR structure are compared with those of a single-section NR sample, which is prepared under the similar condition to that for the first uniform NR section of the two-section sample. All the CL, PL, and EL spectra of the two-section sample (peaked between 520 and 525 nm) are red-shifted from those of the single-section sample (peaked around 490 nm) by >30 nm in wavelength. Also, the emitted spectral widths of the two-section sample become significantly larger than their counterparts of the single-section sample. The PL spectral full-width at half-maximum increases from ~37 to ~61 nm. Such variations are attributed to the higher indium incorporation in the sidewall QWs of the two-section sample due to the stronger strain relaxation in an NR section of a smaller cross-sectional size and the more constituent atom supply from the larger gap volume between neighboring NRs.

© 2015 Optical Society of America

1. Introduction

The widely claimed advantageous features of a core-shell nitride nanorod (NR) light-emitting diode (LED) array include the dislocation-free GaN growth of NR, the larger effective emission area from the NR sidewalls, and the emission from the non-polar or semi-polar InGaN/GaN quantum wells (QWs) on the sidewalls and slant facets for minimizing the quantum-confined Stark effect (QCSE) [1–15 ]. Besides these features, the usually observed broad emission spectrum from such an NR-LED array represents an important property for the application of multi-color or white-light emission without using any phosphor [5, 6, 10, 16, 17 ]. The broad emission from the sidewall QWs in a core-shell NR structure can be attributed to the non-uniform distributions of QW structure and indium content on a sidewall, which are caused by the non-uniform supply of the constituent atoms at different heights in the gap volume between neighboring NRs [6]. It can also be due to the non-uniform strain relaxation condition on the sidewall of an NR such that indium incorporation efficiency for forming QWs varies along height on a sidewall. Strain relaxation is expected to be stronger in an NR of a smaller cross-sectional size. To increase the spectral variation range of the sidewall-QW emission in a core-shell NR LED, a multi-section NR of different cross-sectional sizes in different sections is a useful structure. In such a multi-section NR, the smaller cross-sectional size in an upper uniform section can lead to stronger strain relaxation for further increasing indium incorporation in sidewall-QW growth. Also, the reduced NR cross-sectional size can increase the gap volume size to accommodate more constituent atoms for sidewall-QW growth. The growth of a multi-section NR relies on the formation of a tapering section for reducing the cross-sectional size of the NR. More specifically, a hexagonal flat top-face of a size smaller than the cross section of the NR needs to be formed for the growth of the next section. Recently, based on a pulsed growth technique, this research team has successfully grown regularly-patterned, multi-section GaN NR arrays. After the growth of an NR of a uniform cross section based on the pulsed growth technique with constant supply durations of groups III and V sources, the supply duration of group III source is stepwise decreased for reducing the NR cross-sectional size. After this tapering process, a constant supply duration of group III source is resumed for forming the second uniform section of a smaller cross-sectional size.

In this paper, we demonstrate the significant red-shift and broadening of emission spectrum of a two-section, core-shell, InGaN/GaN QW NR-LED array by comparing its performance with that of a single-section NR-LED array. The overall NR heights of the single- and two-section NR-LED samples are about the same. A two-section NR consists of four portions, including two uniform sections of different cross sectional sizes, a tapering section in between, and a pyramidal structure at the top. A single-section NR consists of two portions, including a uniform NR section and a pyramidal structure at the top. Three periods of InGaN/GaN QW are formed only on the m-plane NR sidewalls in both samples. Cathodoluminescence (CL) and photoluminescence (PL) measurements are undertaken for showing the consistent QW emission behaviors with that of electroluminescence (EL) measurement. In section 2 of this paper, the NR growth and device fabrication procedures are presented. Then, the results of basic optical characterizations, including CL and PL measurements, are reported in section 3. Next, the LED performances of the NR samples are compared in section 4. Discussions are made in section 5. Finally, conclusions are drawn in section 6.

2. Nanorod growth and device fabrication

The growth of the regularly-patterned NR-LED samples starts with the formation of n-GaN NRs on an n-GaN template, which consists of a SiO2 mask with a triangularly-arranged hole pattern. The hole diameter and hole array pitch are 350 and 1200 nm, respectively. The thickness of the SiO2 mask is 80 nm. During the formation of n-GaN NRs, the growth temperature, TMGa, NH3, and silane flow rates in the used metalorganic chemical vapor deposition (MOCVD) reactor are 1035 °C, 15 sccm, 500 sccm, and 12 sccm, respectively. The patterned holes are first filled with n-GaN through a continuous growth process of 30 sec in duration. The out-extended n-GaN NRs are formed through pulsed growth processes. For the single-section NR-LED array sample (sample S), the n-GaN NRs are formed by switching the TMGa and NH3 flows on and off alternatively with the TMGa and NH3 flow durations at 20 and 30 sec, respectively. A growth pause of 1 sec in duration right after a TMGa supply half-cycle is applied. The pulsed growth of n-GaN for 32 cycles leads to an NR height of 1530 nm in sample S. To avoid the growth of an InGaN/GaN QW structure on the NR top, a pointed pyramidal structure is formed at the top through a tapering-growth process by stepwise decreasing the duration of TMGa supply at 15 sec for 3 cycles, 10 sec for 3 cycle, and 5 sec for 20 cycles while the NH3 supply duration is fixed at 30 sec. In this tapering process, the silane flow is turned off such that a pyramidal structure of un-doped GaN is formed at the top of each n-GaN NR. Figure 1(a) shows the tilted scanning electron microscopy (SEM) image of the n-GaN NR-core array of sample S. The pointed pyramidal structure can avoid the formation of a c-plane QW at the top. Also, because the growth rate on the slant facets ({1-101}-plane) of the pyramidal structure is very low, no r-plane QW is formed during the growth of sidewall m-plane QWs [17]. In other words, with the pyramidal structure, only the non-polar QWs can be formed in such an LED for minimizing the QCSE. The growth of un-doped GaN in the pyramidal structure can also increase the local resistance and hence minimize the injected current flow through this portion [17].

 

Fig. 1 (a): Tilted SEM image of the n-GaN NR-core array of sample S. (b): Tilted SEM image of the NR-LED array of sample S. (c): Tilted SEM image of the NR-LED array of sample S after GaZnO deposition. (d)-(f): Similar to parts (a)-(c), respectively, except for sample T.

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For the two-section NR-LED array sample (sample T), the condition for growing the n-GaN NR-core of sample S is used for forming the first NR section with the growth cycle number reduced to 15. Then, a tapering process is undertaken by stepwise reducing the TMGa supply duration at 15 sec for 3 cycles, 10 sec for 3 cycles, and 5 sec for 8 cycles. Again, the NH3 supply and pause durations are fixed. After the tapering process, the pulsed growth with the constant TMGa supply duration at 20 sec is resumed for 15 cycles to form the second uniform NR section of n-GaN. In growing the second uniform NR section, the TMGa flow rate is reduced to 10.5 sccm. The NR-core growth of sample T is completed by forming an un-doped GaN pyramidal structure at the top following the same growth procedure as that for sample S. Figure 1(d) shows the tilted SEM image of the n-GaN NR-core array of sample T. Here, one can clearly see the smaller cross-sectional size in the second uniform NR section.

After the NR cores are completed, three periods of InGaN/GaN QW are deposited with the two-dimensional growth mode. Before QW deposition, the n-GaN NR arrays are dipped into buffer oxide etchant (BOE) for 15 sec to remove the thin SiNx layer formed on NR sidewalls [18]. The SiNx layer is formed during the n-GaN growth with a high silane flow rate. This SiNx layer can actually hinder sidewall growth and accelerate the along-NR-axis growth. However, it needs to be removed for sidewall QW deposition. The BOE dipping duration (15 sec) is chosen for completely removing the sidewall SiNx layer while preserving a certain SiO2-mask thickness for minimizing current leakage in LED operation. The growth temperatures for the InGaN well and GaN barrier layers are 680 and 870 degrees, respectively. As discussed earlier, the design of the NR-core results in the growth of only m-plane QWs on the NR sidewalls. The QW-NR structures before p-GaN deposition are used for CL and PL measurements. The LED structures are completed by depositing a p-GaN layer on the sidewalls at the growth temperature of 960 degrees. Figures 1(b) and 1(e) show the tilted SEM images of the NR-LED arrays of samples S and T, respectively. Here, we can see that the contrast of the cross-section size between the two uniform sections becomes smaller in sample T after the depositions of the QWs and p-GaN layer. In other words, the layer thicknesses of the QWs and p-GaN are larger in the second uniform NR section, when compared with the first uniform section. Next, in a molecular beam epitaxy (MBE) reactor, a conformal, highly-conductive, Ga-doped ZnO (GaZnO) layer is deposited on the NRs at 200 °C in substrate temperature to serve as the transparent conductor for guiding injected current from the top to the NR sidewalls [16, 17, 19 ]. The GaZnO layer is thick enough to connect the neighboring NRs. Before depositing GaZnO, a copper grid with the opening size of 50 μm x 50 μm is placed on the top of an NR array to serve as the hard mask for forming the LED mesas. Figures 1(c) and 1(f) show the tilted SEM images of samples S and T, respectively, after GaZnO deposition. LED process is completed after depositing a layer of Ti (200 nm in thickness) and then a layer of Au (600 nm in thickness) on the top to serve as the p-contact. Also, the n-contact is formed in a region of exposed n-GaN-template surface with 10-nm Ti and 40-nm Au.

Figure 2(a) shows the transmission electron microscopy (TEM) image of an NR of LED sample T. Here, dashed lines are plotted to roughly indicate the boundaries of different materials. We can see that QWs and p-GaN are formed only on the NR sidewalls confirming the low growth rate on the {1-101} slant facets of the top pyramidal structure. The asymmetric GaZnO-layer thickness in the TEM image can be attributed to the removal of certain GaZnO regions left to the NR during TEM sample preparation with a focused-ion beam. This result can also be due to an unexpected atom flow pattern for depositing GaZnO in the MBE chamber. Figures 2(b)-2(d) show the magnified TEM images in the regions indicated by the three dotted-line squares. Here, one can clearly see the three QWs on the sidewalls of the two uniform NR sections as indicated by the (pink) arrows. As shown in Fig. 2(c), on the sidewall of the tapering section between the two uniform sections, the QW structure is unclear. However, a certain InGaN structure may exist. From the TEM image in Fig. 2(a), we can evaluate the surface area of the active region (the QW area on the sidewall) in an LED device of sample T. By reasonably assuming that the NR is roughly bisected for showing the TEM image in Fig. 2(a), we can estimate the lateral width and height of a rectangular sidewall in the first uniform section of the n-GaN NR-core of sample T to give ~300 and ~510 nm, respectively. Also, those of a rectangular sidewall in the second uniform section are estimated to give ~220 and ~860 nm, respectively. Meanwhile, a trapezoidal sidewall in the tapering section has the upper and lower widths of ~220 and ~300 nm, respectively, and the height of ~187 nm. Based on those estimated scales, we can evaluate the total sidewall area of an n-GaN NR-core. This sidewall area is used for approximating the QW surface area on an NR. By multiplying this QW surface area on an NR by the NR density (0.8012 μm−2) and the mesa area (2500 μm2), we can obtain the total QW surface area of an LED device in sample T to give 4696 μm2. A similar evaluation can be applied to sample S with a rectangular sidewall of ~300 and ~1530 nm in width and height, respectively, to give 5516 μm2 in the total QW surface area of an LED device.

 

Fig. 2 (a): TEM image of an NR of LED sample T. Dashed lines are plotted to roughly indicate the boundaries of different materials. (b)-(d): Magnified TEM images in the regions indicated by the three dotted-line squares. Three QWs on the sidewalls of the two uniform NR sections are indicated by the (pink) arrows.

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3. Optical characterization results

Figure 3(a) shows the cross-sectional SEM image of a QW-NR array of sample S with height at ~1.86 μm. Three locations for local CL spectral measurements are marked as 1-3. The CL spectra with the spatial resolution of 40 nm x 30 nm at these locations are shown in Fig. 3(b). Here, the spectral peaks of QW emission at locations 1-3 are 496, 488, and 486 nm, respectively. Because the excitation depths of the n-GaN core and hence the CL emission intensities of GaN are about the same at different sidewall locations, the spectra in Fig. 3(b) are normalized with respect to the individual peak levels of GaN around 366 nm. Here, we can see that the QW emission intensity is the highest at location 2, which is at the middle height on the NR sidewall, followed by that at locations 1 and then 3. The emission of the QWs near the NR bottom is quite weak. The difference of CL spectral peak wavelength between locations 1 and 3 in sample S is 10 nm. The spectrum peaked at 488 nm labeled by “Cross-section” in Fig. 3(b) shows the result of overall sidewall-QW emission. It is obtained by using a large electron beam of about 2.25 μm × 3 μm in size for excitation. Figure 4(a) shows the cross-sectional SEM image of a QW-NR array of sample T with height at ~1.81 μm. Here, locations 1-3 at about the same heights as those in Fig. 3(a) are marked for local CL measurements. Locations 1 and 2 are on the sidewall of the second uniform NR section while location 3 lies on the sidewall of the first uniform section. Location 4 on the tapering section is also marked for CL measurement. Figure 4(b) shows five CL spectra for locations 1-4 and the whole sidewall-QW emission in sample T, which are all normalized with respect to their individual GaN peak levels around 366 nm. The spectral peak wavelengths for locations 1-3 are 530, 514, and 492 nm, respectively, indicating the longer emission wavelengths and the larger spectral difference between the QW portions near the NR top and bottom, when compared with sample S. The difference in spectral peak wavelength between locations 1 and 3 is as large as 38 nm in sample T (only 10 nm in sample S). The spectral peak of the emission from the whole sidewall QWs is 520 nm. Regarding the CL spectrum taken at location 4, the emission is weak and its peak is unclear, confirming the unclear QW structure on the sidewall of the tapering section in sample T. Figures 5(a) and 5(b) show the panchromatic, cross-sectional CL-mapping images of samples S and T, respectively, overlaid on the individual cross-sectional SEM images. Here, we can see that the emission of sample S is generally stronger than that of sample T. In both samples, the top and middle portions of an NR emit more strongly, when compared with the bottom portion. In sample T, the tapering section is essentially dark. It is noted that in Fig. 5(a), although the top and middle portions may look equally bright in CL emission, the middle portion is actually brighter as indicated by the normalized spectral intensity shown in Fig. 3(b).

 

Fig. 3 (a): Cross-sectional SEM image of a QW-NR array of sample S with three locations for local CL spectral measurements being marked as 1-3. (b): CL spectra at locations 1-3, as marked in part (a), and the overall cross-sectional CL spectrum (labeled by “Cross-section”).

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Fig. 4 (a): Cross-sectional SEM image of a QW-NR array of sample T with four locations for local CL spectral measurements being marked as 1-4. (b): CL spectra at locations 1-4, as marked in part (a), and the overall cross-sectional CL spectrum (labeled by “Cross-section”).

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Fig. 5 (a) and (b): Cross-sectional CL mapping images of samples S and T, respectively, overlaid on the individual cross-sectional SEM images.

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Figure 6 shows the PL spectra of the two samples at 10 and 300 K. The PL measurement is excited by a 405-nm InGaN laser diode from the sapphire-substrate side of both QW-NR samples at 6 mW in power. The PL spectral peaks of sample S (T) at 10 and 300 K are 470.7 and 490.9 nm (501.4 and 522.1 nm), respectively. At both temperatures, the PL spectral peak of sample T is red-shifted by more than 30 nm from that of sample S. Also, the spectral full-width at half-maximum (FWHM) is increased from 34.1 nm in sample S to 60.2 nm in sample T (from 36.6 nm in sample S to 61.1 nm in sample T) at 10 (300) K. Figure 7 shows the variations of normalized PL intensity (the left ordinate) and PL spectral peak energy (the right ordinate) with temperature of the two QW-NR samples. From the variations of normalized PL intensity, we can evaluate the internal quantum efficiencies to give 19.6 and 14.3% for samples S and T, respectively. The monotonically decreasing PL spectral peak energy in both samples indicates that their behaviors of carrier localization are weak [20, 21 ].

 

Fig. 6 PL spectra of samples S and T at 10 and 300 K.

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Fig. 7 Variations of normalized PL intensity (the left ordinate) and PL spectral peak energy (the right ordinate) with temperature of the two QW-NR samples.

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4. Characterization results of light-emitting diode arrays

Figure 8 shows the relations between injected current density and applied voltage (J-V curves) of the two NR-LED samples. The current density is obtained via dividing the injected current by the sidewall active area discussed in section 2 for both samples. Here, one can see that the leakage currents under reverse bias up to −5 V are small in both samples (1.07 and 0.97 A/cm2 for samples S and T, respectively, at −5 V). The turn-on voltages for both samples are around 3 V. The device resistance levels of samples S and T are 154 and 195 Ω, respectively. The large resistance levels of the devices are due to their smaller active areas. The device resistivity, which is defined as the product of the active area with device resistance, of sample S (T) is 8.49 x 10−3 (9.15 x 10−3) Ω-cm2. These device resistivity levels are slightly smaller than that of another single-section NR-LED array (1.09 x 10−2 Ω-cm2) published earlier by the same group [17]. All of them are smaller than that of a planar c-plane LED (1.33 x 10−2 Ω-cm2), indicating the reasonable electrical properties in the fabricated NR-LED arrays. The insets of Fig. 8 show the photographs of lit devices of samples S and T when the applied voltage is 8 V.

 

Fig. 8 Relations between injected current density and applied voltage (J-V curves) of the two NR-LED samples. The insets show the photographs of lit devices of samples S and T when the applied voltage is 8 V.

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Figure 9 shows the normalized output intensities per unit active area as functions of injected current density of the two samples. The output intensity per unit active area of sample S is higher than that of sample T. The quasi-linear curves in Fig. 9 indicate that the device heating effects in both samples are weak. Figure 10 shows the variations of normalized efficiency with injected current density of the two samples. The normalized efficiencies of both samples are evaluated via the division of the output intensity per unit active area by the product of the corresponding voltage and injected current density, and then normalized with respect to the maximum level. From the results shown in Fig. 10, one can see that the current density for the maximum efficiency of sample T is slightly larger than that of sample S. The droop slopes with current density in the two samples are about the same. Therefore, we can conclude that the efficiency droop behaviors in the two samples are quite similar.

 

Fig. 9 Output intensities per unit active area as functions of injected current density of the two NR-LED samples.

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Fig. 10 Variations of normalized efficiency with injected current density of the two NR-LED samples.

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Figure 11 shows the LED output spectra at two injected current densities (95 and 325 A/cm2) of the two samples. Again, the spectra of sample T are red-shifted from the corresponding ones of sample S. Also, the spectral widths of sample T are larger than the corresponding values of sample S at both injected current densities. Figure 12 shows the output spectral peak wavelengths as functions of injected current density of the two samples. Here, one can see that in both samples the emission spectra blue-shift with increasing injected current density. This blue-shift trend is not due to the screening of the QCSE. The QCSE is weak in our NR-LED structures with non-polar QWs on the m-plane sidewalls. Instead, it is caused by the extension of the sidewall range covered by injected current from the top at low injected current to the bottom at high injected current [17]. As shown in Figs. 3 and 4 , in both samples, the upper portion of an NR emits light of a longer wavelength. The emission wavelength becomes shorter in the lower portion of an NR. The variation range of emission wavelength in the two-section NR sample is significantly larger than that in the single-section NR sample. The longer-wavelength emission in the upper portion is attributed to the thicker well layer and higher indium content of the QWs in this region. The thicker QWs in the upper portion (the second uniform NR section) of an NR in sample T have been seen in the TEM images shown in Fig. 2. At low injected current, the current mainly flows into the sidewall QWs in the top portion of an NR, which has a relatively lower potential, leading to longer-wavelength emission. As injected current increases, current spreads into the lower portion of an NR for exciting the QWs to emit shorter-wavelength light. As shown in Fig. 12, in the illustrated current density ranges, the blue-shift ranges of samples S and T are 3.8 and 13.8 nm, respectively. The significantly larger blue-shift range in sample T, when compared with sample S, is consistent with the larger difference of CL spectral peak between locations 1 and 3, shown in Figs. 3 and 4 , and the broader PL spectrum, shown in Fig. 6, of this sample. In Fig. 13 , with the left (right) ordinate, we show the variations of spectral FWHM with injected current density of the two samples in terms of meV (nm). Again, the spectral FWHM of sample T is significantly larger than that of sample S. In particular, in terms of meV, the difference in spectral FWHM between the two samples increases with injected current density.

 

Fig. 11 Output spectra at two injected current densities (95 and 325 A/cm2) of the two NR-LED samples.

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Fig. 12 Output spectral peak wavelengths as functions of injected current density of the two NR-LED samples.

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Fig. 13 Variations of EL spectral FWHM with injected current density of the two NR-LED samples in terms of meV (nm) with the left (right) ordinate.

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5. Discussions

It is noted that the EL spectra measured in the NR-LED structures are red-shifted from those in the PL and CL measurements with the QW-NR structures. This is so because the p-i-n configuration in an LED structure and the applied forward-biased voltage in EL measurement can tilt the potentials of the non-polar QWs for red-shifting the emission spectrum. Also, the overgrowth of the p-GaN layer at a high temperature (960 °C) can produce a thermal annealing effect on the QWs for further red-shifting the emission spectrum [22]. From the PL and EL measurements, we can observe the larger emission spectral width in the two-section NR sample. From the local CL measurement, we can see that this broader emission spectral width is caused by the larger emission spectral difference between the top and bottom portions of the sidewall QWs. This larger difference is attributed to the formation of the second uniform section of a smaller cross-sectional size. Actually, the growth of the two-section NR leads to the red-shifts and broadenings of emission spectra from the QW portions at all heights (see Figs. 3 and 4 ). It is speculated that the indium contents of the QW portions at all heights become higher in sample T, when compared with sample S. The increased indium content in sample T may have two causes, including the stronger strain relaxation and the larger gap volume in the two-section structure. An NR section of a smaller cross-sectional size is expected to be more strain relaxed such that indium incorporation can be enhanced. Also, because of the larger gap volume between NRs, more indium atoms can fall into this volume for being adsorbed by the NR sidewalls. Since more constituent atoms are available in the upper portion of the NR array, the QW thickness and indium content can be larger in this QW portion, leading to a longer emission wavelength. The atom supplies for depositing the sidewall layers, including QWs and p-GaN, have two sources: (1) the direct downward flow of constituent atoms from the top and (2) those constituent atoms flowing downward to the bottom in the gap region between NRs and then migrating upward along the NR sidewalls. The first contribution of direct downward-flow atoms can be more important in determining the sidewall layer thickness. Therefore, the sidewall layers are usually thicker in the upper portion of an NR. In a multi-section NR, the smaller cross-sectional size of the upper portion results in a larger gap volume and hence more atom supply for sidewall deposition to produce even thicker sidewall layers. Regarding the thin sidewall-QW layer in the tapering section, it is simply due to the low growth rate on an r-plane surface.

In Figs. 3(b), 4(b), 5(a), and 5(b) , we can see that on a sidewall, the strongest emission is distributed around middle height in both samples. The height on a sidewall for the strongest emission depends on QW growth temperature [10]. When the sidewall QWs are grown at a lower temperature, more abundant constituent atoms are available near the bottom of the gap volume such that the QW quality in this portion can be higher for stronger emission. As QW growth temperature increases, the higher kinetic energy of the constituent atoms results in a more abundant supply for forming higher-quality QWs and hence stronger emission at a higher position on a sidewall. To achieve overall longer-wavelength emission from such an NR-LED device, the QW growth temperature needs to be reduced for increasing indium incorporation. In this situation, the QW quality in the lower portion of an NR is higher and can dominate the overall emission spectrum. Nevertheless, in any situation, indium content decreases with decreasing height on a sidewall. This variation trend can counterbalance the effect of spectral red shift by decreasing the QW growth temperature. Therefore, the formation of a multi-section NR by stepwise decreasing the cross-sectional size can be a more effective method for elongating the emission wavelength. By keeping the QW growth temperature at a certain high value, the smaller cross-sectional size of an upper NR section can lead to an effective red shift of the overall sidewall emission spectrum. Besides, the overall emission spectral width can be increased for implementing a multi-color or white-light LED device without using a phosphor.

It is also noted that the difference in PL spectral FWHM at room temperature between the two samples is quite large (61.1 nm in sample T versus 36.6 nm in sample S). However, that in EL spectral FWHM is relatively smaller. For instance, at ~325 A/cm2 in injected current density, the EL spectral FWHMs of samples S and T are ~45 and ~55 nm, respectively. The weaker spectral broadening in EL emission, when compared with PL emission, is attributed to the non-uniform current coverage on the sidewall QWs. It is speculated that in the QW portion of stronger CL emission shown in Fig. 5(a) or 5(b), the higher QW quality can lead to lower local resistance such that more injected current flows through this region for further increasing its emission intensity. In other words, besides the higher emission efficiency (higher QW quality), the higher local current density makes the predominant contribution of EL emission intensity from this portion such that the overall EL spectral width cannot be significantly increased in sample T. The uniformity of QW quality on a sidewall of an NR needs to be improved.

6. Conclusions

In summary, we have demonstrated the growth of a two-section, core-shell, InGaN/GaN QW NR-array LED device based on a pulsed growth technique with MOCVD. A two-section n-GaN NR was grown through a tapering process for forming two uniform NR sections of different cross-sectional sizes. The CL, PL, and EL characterization results of the two-section NR structure were compared with those of a single-section NR sample, which was prepared under the similar condition to that for the first uniform NR section of the two-section sample. It was found that all the CL, PL, and EL spectra of the two-section sample (peaked between 520 and 525 nm) were red-shifted from those of the single-section sample (peaked around 490 nm) by >30 nm in wavelength. Also, the emitted spectral widths of the two-section sample became significantly larger than their counterparts of the single-section sample. The PL spectral FWHM increased from ~37 to ~61 nm. Such variations were attributed to the higher indium incorporation in the sidewall QWs of the two-section sample due to the stronger strain relaxation in an NR section of a smaller cross-sectional size and the more constituent atom supply from the larger gap volume between neighboring NRs.

Acknowledgments

This research was supported by Ministry of Science and Technology, Taiwan, The Republic of China, under the grants of MOST 103-2120-M-002-002, NSC 102-2221-E-002-204-MY3, and MOST 103-2221-E-002-139, by National Taiwan University (103R890951 and 103R890952), and by US Air Force Scientific Research Office under the contract of AOARD-14-4105.

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6. C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013). [CrossRef]  

7. W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011). [CrossRef]  

8. W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010). [CrossRef]   [PubMed]  

9. X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013). [CrossRef]  

10. C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014). [CrossRef]   [PubMed]  

11. Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012). [CrossRef]   [PubMed]  

12. T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012). [CrossRef]   [PubMed]  

13. Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014). [CrossRef]  

14. B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014). [CrossRef]  

15. B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015). [CrossRef]  

16. H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013). [CrossRef]   [PubMed]  

17. C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014). [CrossRef]   [PubMed]  

18. C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014). [CrossRef]  

19. Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014). [CrossRef]   [PubMed]  

20. M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008). [CrossRef]  

21. Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000). [CrossRef]  

22. C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012). [CrossRef]   [PubMed]  

References

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  1. S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
    [Crossref] [PubMed]
  2. X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
    [Crossref]
  3. Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
    [Crossref]
  4. T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
    [Crossref]
  5. C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
    [Crossref] [PubMed]
  6. C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
    [Crossref]
  7. W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
    [Crossref]
  8. W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
    [Crossref] [PubMed]
  9. X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
    [Crossref]
  10. C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
    [Crossref] [PubMed]
  11. Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012).
    [Crossref] [PubMed]
  12. T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
    [Crossref] [PubMed]
  13. Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
    [Crossref]
  14. B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
    [Crossref]
  15. B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
    [Crossref]
  16. H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
    [Crossref] [PubMed]
  17. C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
    [Crossref] [PubMed]
  18. C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
    [Crossref]
  19. Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
    [Crossref] [PubMed]
  20. M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
    [Crossref]
  21. Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
    [Crossref]
  22. C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
    [Crossref] [PubMed]

2015 (1)

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

2014 (6)

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
[Crossref] [PubMed]

2013 (3)

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

2012 (4)

2011 (1)

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

2010 (1)

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

2009 (2)

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

2008 (1)

M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
[Crossref]

2006 (2)

S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
[Crossref] [PubMed]

X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
[Crossref]

2000 (1)

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Ahn, B.

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Amano, H.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Bae, S. Y.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Bergbauer, W.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Butzen, E.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Cao, W.

Chang, W. M.

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Chen, C. Y.

Chen, H. S.

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Chen, H. T.

Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
[Crossref] [PubMed]

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Chen, L. C.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Chen, W. C.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Chen, W. H.

Chen, Y. S.

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Cheng, Y. C.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Cherns, D.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
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Christiansen, S.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
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Chung, W. L.

Chuo, C. C.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Chyi, J. I.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
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Dapkus, P. D.

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
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T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
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Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012).
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Dieker, C.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
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Fairchild, M.

X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
[Crossref]

Feng, S. W.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Fündling, S.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Griffiths, I.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Haab, A.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Hardtdegen, H.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Heilmann, M.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Hersee, S. D.

X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
[Crossref]

S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
[Crossref] [PubMed]

Honda, Y.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Hsieh, C.

Hsu, C.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Hsu, M. C.

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Hsu, T. C.

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Hsu, T.-C.

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

Hu, X.

Huang, J. J.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Imura, M.

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Jahn, U.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Jung, B. O.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Kato, Y.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Kiang, Y. W.

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
[Crossref] [PubMed]

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Kim, S. Y.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

Kölper, Ch.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Kubota, M.

M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
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Lähnemann, J.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Ledig, J.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Lee, C. M.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Lee, D. S.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

B. O. Jung, S. Y. Bae, Y. Kato, M. Imura, D. S. Lee, Y. Honda, and H. Amano, “Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique,” CrystEngComm 16(11), 2273–2282 (2014).
[Crossref]

Lee, J. Y.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

Lee, S.

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
[Crossref]

Li, S. F.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Liao, C. C.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Liao, C. H.

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Lin, C. H.

Lin, Y. S.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Lin, Y. T.

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
[Crossref]

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012).
[Crossref] [PubMed]

Linder, N.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Liu, T. C.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Ma, K. J.

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Mandl, M.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Mohajerani, M. S.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Nakajima, Y.

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
[Crossref]

Nutt, S. R.

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

O’Brien, J. D.

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Ohta, H.

M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
[Crossref]

Okamoto, K.

M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
[Crossref]

Riechert, H.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Roder, C.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Sarkissian, R.

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Shen, K. C.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Shiao, W. Y.

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Shih, P. Y.

Spiecker, E.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Steegmüller, U.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

Stewart, L. S.

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Strassburg, M.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Su, C. Y.

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

Sun, X.

X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
[Crossref]

S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
[Crossref] [PubMed]

Tanaka, T.

M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Temperature dependence of polarized photoluminescence from nonpolar m-plane InGaN multiple quantum wells for blue laser diodes,” Appl. Phys. Lett. 92(1), 011920 (2008).
[Crossref]

Tang, T. Y.

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Tessarek, C.

C. Tessarek, M. Heilmann, E. Butzen, A. Haab, H. Hardtdegen, C. Dieker, E. Spiecker, and S. Christiansen, “The role of Si during the growth of GaN micro- and nanorods,” Cryst. Growth Des. 14(3), 1486–1492 (2014).
[Crossref]

Ting, S. Y.

Trampert, A.

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Tu, C. G.

Waag, A.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Wang, X.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
[Crossref] [PubMed]

X. Wang, X. Sun, M. Fairchild, and S. D. Hersee, “Fabrication of GaN nanowire arrays by confined epitaxy,” Appl. Phys. Lett. 89(23), 233115 (2006).
[Crossref]

Wehmann, H. H.

X. Wang, S. F. Li, M. S. Mohajerani, J. Ledig, H. H. Wehmann, M. Mandl, M. Strassburg, U. Steegmüller, U. Jahn, J. Lähnemann, H. Riechert, I. Griffiths, D. Cherns, and A. Waag, “Continuous-flow MOVPE of Ga-Polar GaN column arrays and core–shell LED structures,” Cryst. Growth Des. 13(8), 3475–3480 (2013).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
[Crossref]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
[Crossref] [PubMed]

Yang, C. C.

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
[Crossref] [PubMed]

C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
[Crossref] [PubMed]

Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
[Crossref] [PubMed]

H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
[Crossref] [PubMed]

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
[Crossref] [PubMed]

C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
[Crossref] [PubMed]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Y. S. Lin, K. J. Ma, C. Hsu, S. W. Feng, Y. C. Cheng, C. C. Liao, C. C. Yang, C. C. Chuo, C. M. Lee, and J. I. Chyi, “Dependence of composition fluctuation on indium content in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 77(19), 2988 (2000).
[Crossref]

Yao, C. L.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Yao, Y. F.

C. H. Liao, C. G. Tu, W. M. Chang, C. Y. Su, P. Y. Shih, H. T. Chen, Y. F. Yao, C. Hsieh, H. S. Chen, C. H. Lin, C. K. Yu, Y. W. Kiang, and C. C. Yang, “Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition,” Opt. Express 22(14), 17303–17319 (2014).
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Y. F. Yao, H. T. Chen, C. Y. Su, C. Hsieh, C. H. Lin, Y. W. Kiang, and C. C. Yang, “Phosphor-free, white-light LED under alternating-current operation,” Opt. Lett. 39(22), 6371–6374 (2014).
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C. G. Tu, C. H. Liao, Y. F. Yao, H. S. Chen, C. H. Lin, C. Y. Su, P. Y. Shih, W. H. Chen, E. Zhu, Y. W. Kiang, and C. C. Yang, “Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Express 22(S7), A1799–A1809 (2014).
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H. S. Chen, Y. F. Yao, C. H. Liao, C. G. Tu, C. Y. Su, W. M. Chang, Y. W. Kiang, and C. C. Yang, “Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array,” Opt. Lett. 38(17), 3370–3373 (2013).
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C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

C. H. Liao, W. M. Chang, H. S. Chen, C. Y. Chen, Y. F. Yao, H. T. Chen, C. Y. Su, S. Y. Ting, Y. W. Kiang, and C. C. Yang, “Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod,” Opt. Express 20(14), 15859–15871 (2012).
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C. Y. Chen, C. Hsieh, C. H. Liao, W. L. Chung, H. T. Chen, W. Cao, W. M. Chang, H. S. Chen, Y. F. Yao, S. Y. Ting, Y. W. Kiang, C. C. Yang, and X. Hu, “Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode,” Opt. Express 20(10), 11321–11335 (2012).
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Yeh, J. H.

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

Yeh, T. W.

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
[Crossref]

Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012).
[Crossref] [PubMed]

T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Yu, C. K.

Zhu, E.

Adv. Funct. Mater. (1)

Y. T. Lin, T. W. Yeh, Y. Nakajima, and P. D. Dapkus, “Catalyst-free GaN nanorods synthesized by selective area growth,” Adv. Funct. Mater. 24(21), 3162–3171 (2014).
[Crossref]

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J. Appl. Phys. (3)

C. H. Liao, W. M. Chang, Y. F. Yao, H. T. Chen, C. Y. Su, C. Y. Chen, C. Hsieh, H. S. Chen, C. G. Tu, Y. W. Kiang, C. C. Yang, and T.-C. Hsu, “Cross-sectional sizes and emission wavelengths of regularly patterned GaN and core-shell InGaN/GaN quantum-well nanorod arrays,” J. Appl. Phys. 113(5), 054315 (2013).
[Crossref]

Y. S. Chen, W. Y. Shiao, T. Y. Tang, W. M. Chang, C. H. Liao, C. H. Lin, K. C. Shen, C. C. Yang, M. C. Hsu, J. H. Yeh, and T. C. Hsu, “Threading dislocation evolution in patterned GaN nanocolumn growth and coalescence overgrowth,” J. Appl. Phys. 106(2), 023521 (2009).
[Crossref]

T. Y. Tang, W. Y. Shiao, C. H. Lin, K. C. Shen, J. J. Huang, S. Y. Ting, T. C. Liu, C. C. Yang, C. L. Yao, J. H. Yeh, T. C. Hsu, W. C. Chen, and L. C. Chen, “Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy,” J. Appl. Phys. 105(2), 023501 (2009).
[Crossref]

J. Cryst. Growth (1)

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “N-face GaN nanorods: continuous-flux MOVPE growth and morphological properties,” J. Cryst. Growth 315(1), 164–167 (2011).
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Nano Energy (1)

B. O. Jung, S. Y. Bae, S. Y. Kim, S. Lee, J. Y. Lee, D. S. Lee, Y. Kato, Y. Honda, and H. Amano, “Highly ordered catalyst-free InGaN/GaN core–shell architecture arrays with expanded active area region,” Nano Energy 11, 294–303 (2015).
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S. D. Hersee, X. Sun, and X. Wang, “The controlled growth of GaN nanowires,” Nano Lett. 6(8), 1808–1811 (2006).
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T. W. Yeh, Y. T. Lin, L. S. Stewart, P. D. Dapkus, R. Sarkissian, J. D. O’Brien, B. Ahn, and S. R. Nutt, “InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays,” Nano Lett. 12(6), 3257–3262 (2012).
[Crossref] [PubMed]

Nanotechnology (2)

Y. T. Lin, T. W. Yeh, and P. D. Dapkus, “Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition,” Nanotechnology 23(46), 465601 (2012).
[Crossref] [PubMed]

W. Bergbauer, M. Strassburg, Ch. Kölper, N. Linder, C. Roder, J. Lähnemann, A. Trampert, S. Fündling, S. F. Li, H. H. Wehmann, and A. Waag, “Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells,” Nanotechnology 21(30), 305201 (2010).
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Opt. Express (4)

Opt. Lett. (2)

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Figures (13)

Fig. 1
Fig. 1 (a): Tilted SEM image of the n-GaN NR-core array of sample S. (b): Tilted SEM image of the NR-LED array of sample S. (c): Tilted SEM image of the NR-LED array of sample S after GaZnO deposition. (d)-(f): Similar to parts (a)-(c), respectively, except for sample T.
Fig. 2
Fig. 2 (a): TEM image of an NR of LED sample T. Dashed lines are plotted to roughly indicate the boundaries of different materials. (b)-(d): Magnified TEM images in the regions indicated by the three dotted-line squares. Three QWs on the sidewalls of the two uniform NR sections are indicated by the (pink) arrows.
Fig. 3
Fig. 3 (a): Cross-sectional SEM image of a QW-NR array of sample S with three locations for local CL spectral measurements being marked as 1-3. (b): CL spectra at locations 1-3, as marked in part (a), and the overall cross-sectional CL spectrum (labeled by “Cross-section”).
Fig. 4
Fig. 4 (a): Cross-sectional SEM image of a QW-NR array of sample T with four locations for local CL spectral measurements being marked as 1-4. (b): CL spectra at locations 1-4, as marked in part (a), and the overall cross-sectional CL spectrum (labeled by “Cross-section”).
Fig. 5
Fig. 5 (a) and (b): Cross-sectional CL mapping images of samples S and T, respectively, overlaid on the individual cross-sectional SEM images.
Fig. 6
Fig. 6 PL spectra of samples S and T at 10 and 300 K.
Fig. 7
Fig. 7 Variations of normalized PL intensity (the left ordinate) and PL spectral peak energy (the right ordinate) with temperature of the two QW-NR samples.
Fig. 8
Fig. 8 Relations between injected current density and applied voltage (J-V curves) of the two NR-LED samples. The insets show the photographs of lit devices of samples S and T when the applied voltage is 8 V.
Fig. 9
Fig. 9 Output intensities per unit active area as functions of injected current density of the two NR-LED samples.
Fig. 10
Fig. 10 Variations of normalized efficiency with injected current density of the two NR-LED samples.
Fig. 11
Fig. 11 Output spectra at two injected current densities (95 and 325 A/cm2) of the two NR-LED samples.
Fig. 12
Fig. 12 Output spectral peak wavelengths as functions of injected current density of the two NR-LED samples.
Fig. 13
Fig. 13 Variations of EL spectral FWHM with injected current density of the two NR-LED samples in terms of meV (nm) with the left (right) ordinate.

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