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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 3 — Feb. 10, 2014
  • pp: 3585–3592
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Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH3 interrupted etching

Ji-Su Son, Yoshio Honda, and Hiroshi Amano  »View Author Affiliations


Optics Express, Vol. 22, Issue 3, pp. 3585-3592 (2014)
http://dx.doi.org/10.1364/OE.22.003585


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Abstract

Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching. Subsequently, a 2-µm-thick Si-doped a-GaN layer was regrown on the etched a-GaN layer. A fully coalescent n-type a-GaN layer with a low threading dislocation density (~7.5 × 108 cm−2) and a low basal stacking fault density (~1.8 × 105 cm−1) was obtained. Compared with a planar sample, the full width at half maximum of the (11-20) X-ray rocking curve was significantly decreased to 518 arcsec along the c-axis direction and 562 arcsec along the m-axis direction.

© 2014 Optical Society of America

1. Introduction

Over the few decades, conventional c-plane III-V nitride light emitting diodes (LEDs) have achieved remarkable increases in performance owing to dramatic improvements in the quality of nitride materials. However, the device performance is strongly restricted by strong built-in electric fields originating from strain-induced piezoelectric and spontaneous polarizations in the [0001] direction. These polarization-induced fields along the c-axis cause the quantum-confined Stark effect, which leads to reduced radiative recombination rates in quantum wells (QWs) [1

1. H. Amano, N. Sawaki, I. Akasaki, and Y. Toyoda, “Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer,” Appl. Phys. Lett. 48(5), 353–355 (1986). [CrossRef]

4

4. P. Lefebvre, A. Morel, M. Gallart, T. Taliercio, J. Allegre, B. Gil, H. Mathieu, B. Damilano, N. Grandjean, and J. Massies, “High internal electric field in a graded-width InGaN/GaN quantum well: accurate determination by time-resolved photoluminescence spectroscopy,” Appl. Phys. Lett. 78(9), 1252–1254 (2001). [CrossRef]

]. To overcome these problems, nonpolar and semipolar GaN have attracted considerable attention in the research field. However, nonpolar and semipolar GaN grown on sapphire substrates generally suffer from a high density of threading dislocations (TDs) and basal stacking faults (BSFs) owing to the high Ga-polar to N-polar wing growth rate ratio and the large lattice mismatch between GaN and the substrate [5

5. T. Paskova, R. Kroeger, S. Figge, D. Hommel, V. Darakchieva, B. Monemar, E. Preble, A. Hanser, N. M. Williams, and M. Tutor, “High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire,” Appl. Phys. Lett. 89(5), 051914 (2006). [CrossRef]

9

9. H. Yamada, Y. Iso, M. Saito, H. Hirasawa, N. Fellows, H. Masui, K. Fujito, J. S. Speck, S. P. DenBaars, and S. Nakamura, “Comparison of InGaN/GaN light emitting diodes grown on m-plnae and a-plane bulk GaN substrates,” Phys. Status Solidi 2, 89–91 (2008).

].

Epitaxial lateral overgrowth (ELOG) is one of the most commonly used techniques to reduce the high defect density and improve crystalline quality. Although nonpolar a-plane (11-20) GaN (a-GaN) grown by ELOG has a low defect density in the wing area (on the mask), the window area (where these is no mask) still has a high defect density [6

6. X. Ni, Ü. Özgür, H. Morkoç, Z. Liliental-Weber, and H. O. Everitt, “Epitaxial lateral overgrowth of a-plane GaN by metalorganic chemical vapor deposition,” J. Appl. Phys. 102(5), 053506 (2007). [CrossRef]

,10

10. C. Chen, J. Yang, H. Wang, J. Zhang, V. Adivarahan, M. Gaevski, E. Kuokstis, Z. Gong, M. Su, and M. A. Khan, “Lateral epitaxial overgrowth of fully coalesced a-plane GaN on r-plane sapphire,” Jpn. J. Appl. Phys. Part 2 42(6B), L640–L642 (2003). [CrossRef]

12

12. J. S. Son, Y. Honda, M. Yamaguchi, H. Amano, K. H. Baik, Y. G. Seo, and S. M. Hwang, “Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates,” Thin Solid Films 546, 108–113 (2013). [CrossRef]

]. The high density of TDs in the window area can act as nonradiative recombination centers in multiple-quantum wells (MQWs) and decrease the LED device performance.

In this study, we report on nonpolar a-GaN layers with a low overall defect density, a high crystalline quality, and a good optical property grown on r-plane (1-102) sapphire substrates with −0.2°-off-axis tilted in the c-axis [0001] direction by metalorganic vapor phase epitaxy.

2. Experimental details

Nonpolar a-plane GaN layers were grown on r-plane sapphire substrates using pulse NH3 interrupted etching method. Trimethylgallium, trimethylindium, methylsilane, bis-magnesium, and ammonia (NH3) were used as the source materials of Ga, In, Si, Mg, and N, respectively.

Figure 1
Fig. 1 Schematic diagram of a-GaN layer growth: (a) a-GaN layer grown on r-plane sapphire substrate with SiO2 nanopillar mask, (b) fabrication of SiO2 nanopillar mask on a-GaN layer, (c) a-GaN layer etching process, (d) etched a-GaN layer, and (e) fully coalescent a-GaN layer.
depicts a schematic showing the growth of a-GaN using a pulse NH3 interrupted etching process. First, a 4-µm-thick undoped a-GaN layer, which was grown by modified two-step growth [13

13. J. L. Hollander, M. J. Kappers, C. McAleese, and C. J. Humphreys, “Improvements in a-plane GaN crystal quality by a two-step growth process,” Appl. Phys. Lett. 92(10), 101104 (2008). [CrossRef]

], was deposited on an r-plane sapphire substrate with a SiO2 nanopillar mask of 230 nm diameter by nanoimprint lithography (NIL) as shown in Fig. 1(a). Experimental details of the growth of the undoped a-GaN layer using the SiO2 nanopillar mask were previously reported [14

14. J. S. Son, C. Miao, Y. Honda, M. Yamaguchi, H. Amano, Y. G. Seo, S. M. Hwang, and K. H. Baik, “Effects of nano- and microscale SiO2 masks on the growth of a-plane GaN layers on r-plane sapphire,” Jpn. J. Appl. Phys. 52(8S), 08JC04 (2013). [CrossRef]

]. A SiO2 nanopillar mask was again fabricated on the fully coalescent undoped a-GaN layer by NIL, as shown in Fig. 1(b), to enable the etching of a large area of GaN except for that below the SiO2 mask and obtain the rapid coalescence of a-GaN during the regrowth process. Figure 1(c) shows the a-GaN layer etching process below the fabricated SiO2 nanopillar mask. In general, GaN layers can be only etched along anisotropic direction by typical plasmas and wet etching. However, we tried the pulse NH3 interrupted etching method to obtain irregular and rough etched GaN surface, which can effectively bend the TDs.

It is well known that GaN can decompose during epitaxial growth. The decomposition of GaN can be described by several mechanisms, which are into gaseous Ga and N, liquid Ga and N, and sublimation of GaN as a diatomic or polymeric product [15

15. Z. A. Munir and A. W. Searcy, “Activation energy for the sublimation of gallium nitride,” J. Chem. Phys. 42(12), 4223–4228 (1965). [CrossRef]

,16

16. D. D. Koleske, A. E. Wickenden, R. L. Henry, J. C. Culbertson, and M. E. Twigg, “GaN decomposition in H2 and N2 at MOVPE temperatures and pressures,” J. Cryst. Growth 223(4), 466–483 (2001). [CrossRef]

]. The GaN decomposition rate is generally controlled by the temperature, pressure, and gas flow rate. To etch the a-GaN layer, we utilized the GaN decomposition phenomena. The reactor was set to 1050 °C and 75 Torr. A mixture of pure NH3 and H2 at a standard 5 L/min flow rate, which is the optimized flow rate in our reactor for obtaining uniformly etched samples, was injected, resulting in the rough and deep etching of the a-GaN layer. The mixture was injected for 10 sec for slow etching, then the NH3 flow was interrupted for 9 sec for fast etching. This was repeated 50 times in the initial etching of the a-GaN layer. Then, the a-GaN layer was sequentially etched for 30 min in the mixed NH3 and H2 flow to obtain a deeply etched a-GaN layer.

This pulse NH3 interrupted etching process can be used to obtain different GaN etching rates by changing the gas ambient [16

16. D. D. Koleske, A. E. Wickenden, R. L. Henry, J. C. Culbertson, and M. E. Twigg, “GaN decomposition in H2 and N2 at MOVPE temperatures and pressures,” J. Cryst. Growth 223(4), 466–483 (2001). [CrossRef]

]. Figures 2(a)
Fig. 2 Bird’s-eye views of etched a-GaN layers after pulse NH3 interrupted etching (50 cycles) in (a) mixed NH3 and H2 flow, and (d) mixed NH3 and N2 flow. (e) Etched a-GaN layer after pulse NH3 interrupted etching (50 cycles) and sequential etching (30 min) in mixed NH3 and N2 flow. (b) Plan-view and (c) cross-sectional SEM images along m-direction (inset: along c-direction) of a-GaN layer after pulse NH3 interrupted etching in mixed NH3 and H2 flow. (f) Cross-sectional and plan-view (inset) SEM images of a-GaN layer after sequential etching (45 min) in mixed NH3 and H2 flow.
, 2(d), and 2(e) show images of etched a-GaN layers obtained under different gas flows. Figures 2(a) and 2(d) show etched a-GaN layers after 50 cycles of the pulse etching process using mixed NH3 and H2 and mixed NH3 and N2 flows, respectively. In the case of the mixed NH3 and N2 flow, the a-GaN layer was anistropically etched along the substrate. Even though the etched a-GaN layer was sequentially more etched for 30 min in the mixed NH3 and N2 flow, as shown in Fig. 2(e), it was only partially etched and had a small etching depth compared with that etched in the mixed NH3 and H2 flow as shown in Fig. 2(c). This was due to the GaN decomposition rate in the N2 flow being much lower than that in the H2 flow.

Figure 1(d) shows the etched a-GaN layer with an irregular shape after pulse NH3 interrupted etching in the mixed NH3 and H2 flow. During the regrowth of a 2-µm-thick n-type a-GaN layer, a number of microscale voids formed under the SiO2 nanopillar mask during the coalescence of the a-GaN layer as shown in Fig. 1(e).

3. Results and discussion

Figure 2 shows a scanning electron microscopy (SEM) image of the etched a-GaN layer after pulse NH3 interrupted etching. In the plan-view SEM images, we observed the etching of the entire a-GaN layer excluding the SiO2 nanopillar mask as shown in Fig. 2(b). The irregular shape of the a-GaN layer along c- and m-directions etched to ~1.3 µm depth was observed in cross-sectional SEM images as shown in Fig. 2(c). The irregular and rough surface of the a-GaN layer can effectively bend the TDs and prevent their propagation during the lateral overgrowth process. Figure 2(f) shows the etched a-GaN layer after the sequential etching process (45 min) in the mixed NH3 and H2 flow. The sequential etching of GaN resulted in the poor uniformity of the etching depth and area owing to the constant etching rate. Triangular etching marks were also observed around the SiO2 mask as shown in the inset.

To investigate the density of TDs and BSFs, a fully coalescent n-type a-GaN layer was observed by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). It is well known that TDs can be characterized when g = 11-20 via the |g·b| criterion in TEM imaging (g is the diffraction vector and b is the Burgers vector). Under a two-beam condition with g = 1-100, intrinsic I1-type BSFs are terminated by Frank–Shockley partial dislocations (PDs) with Burgers vector b = 1/6<20-23> [17

17. M. D. Craven, S. H. Lim, F. Wu, J. S. Speck, and S. P. DenBaars, “Structural characterization of nonpolar (11-20) a-plane GaN thin films grown on (1-102) r-plane sapphire,” Appl. Phys. Lett. 81(3), 469–471 (2002). [CrossRef]

,18

18. M. A. Moram, C. F. Johnston, J. L. Hollander, M. J. Kappers, and C. J. Humphreys, “Understanding x-ray diffraction of nonpolar gallium nitride films,” J. Appl. Phys. 105(11), 113501 (2009). [CrossRef]

]. Figures 3(a)
Fig. 3 (a) Cross-sectional SEM image of fully coalescent n-type a-GaN layer. Cross-sectional STEM and TEM images viewed along m-direction with g = 11-20: (b) fully coalescent n-type a-GaN layer (STEM), (c) SiO2 nanopillar mask area on r-plane sapphire substrate (TEM), and (d) magnification of void area (TEM).
and 3(b) show cross-sectional SEM and BF-STEM images of a fully coalescent n-type a-GaN layer, respectively. A number of nano- and microscale voids with an irregular shape were observed around the etched GaN and SiO2 nanopillar mask areas. The origin of these voids can be explained by the mass transport of GaN [19

19. S. Nitta, M. Kariya, T. Kashima, S. Yamaguchi, H. Amano, and I. Akasaki, “Mass transport and reduction of threading dislocation in GaN,” Appl. Surf. Sci. 159–160, 421–426 (2000). [CrossRef]

], which led to the bending and interruption of TDs. The TEM image in Fig. 3(d) shows clear evidence of mass transport. The upper area in which mass transport occurred clearly has a low TD density. Also, the light output power of LEDs can be increased via light scattering and reflection at the interface between voids and an a-GaN layer [20

20. P. Vennéguès, B. Beaumont, V. Bousquet, M. Vaille, and P. Gibart, “Reduction mechanisms for defect densities in GaN using one- or two-step epitaxial lateral overgrowth methods,” J. Appl. Phys. 87(9), 4175–4181 (2000). [CrossRef]

,21

21. J. K. Sheu, S. J. Tu, M. L. Lee, Y. H. Yeh, C. C. Yang, F. W. Huang, W. C. Lai, C. W. Chen, and G. C. Chi, “Enhanced light output of GaN-based light-emitting diodes with embedded voids formed on Si-implanted GaN layers,” IEEE Electron Device Lett. 32(10), 1400–1402 (2011). [CrossRef]

]. Figure 3(c) shows the nanopillar SiO2 mask area on an r-plane sapphire substrate. As illustrated in Fig. 1(a), a high density of TDs was observed in window areas owing to the use of the conventional ELOG process. The overall density of TDs was reduced from ~1.2 × 1010 cm−2 in a planar a-GaN layer (not shown here) to ~7.5 × 108 cm−2 in the a-GaN layer subjected to the pulse NH3 interrupted etching process. It is notable that although this TD density is higher than those for conventional ELOG samples in the wing area [6

6. X. Ni, Ü. Özgür, H. Morkoç, Z. Liliental-Weber, and H. O. Everitt, “Epitaxial lateral overgrowth of a-plane GaN by metalorganic chemical vapor deposition,” J. Appl. Phys. 102(5), 053506 (2007). [CrossRef]

,10

10. C. Chen, J. Yang, H. Wang, J. Zhang, V. Adivarahan, M. Gaevski, E. Kuokstis, Z. Gong, M. Su, and M. A. Khan, “Lateral epitaxial overgrowth of fully coalesced a-plane GaN on r-plane sapphire,” Jpn. J. Appl. Phys. Part 2 42(6B), L640–L642 (2003). [CrossRef]

12

12. J. S. Son, Y. Honda, M. Yamaguchi, H. Amano, K. H. Baik, Y. G. Seo, and S. M. Hwang, “Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates,” Thin Solid Films 546, 108–113 (2013). [CrossRef]

], we can fabricate an LED device using an epilayer with uniform low defect density.

Figure 4
Fig. 4 Plan-view TEM images with g = 1–100 of (a) planar a-GaN layer and (b) etched a-GaN layer.
shows plan-view TEM images with g = 1-100 of a planar a-GaN layer and an a-GaN layer subjected to the etching process to observe BSFs, which are generated between the nucleation layer and the substrate and propagate through the a-GaN layer to the surface. The density of BSFs in the direction perpendicular to the c-axis [0001] was reduced from ~9.7 × 105 cm−1 in the planar a-GaN layer to ~1.8 × 105 cm−1 in the etched a-GaN layer. However, BSF terminations and short BSFs were observed more frequently in the planar a-GaN layer than in the etched a-GaN layer. This indicates that etching the a-GaN layer reduced the density of PDs, which terminate BSFs and prismatic stacking faults [22

22. D. N. Zakharov, Z. Liliental-Weber, B. Wagner, Z. J. Reitmeier, E. A. Preble, and R. F. Davis, “Structural TEM study of nonpolar a-plane gallium nitride grown on (11-20) 4H-SiC by organometallic vapor phase epitaxy,” Phys. Rev. B 71(23), 235334 (2005). [CrossRef]

].

To determine the optical properties of a-GaN LED devices, five-period InGaN (5 nm)/GaN (12 nm) MQW layers were grown on an n-type a-GaN layer with a doping concentration of 3 × 1018 cm−3 under N2 ambient. Subsequently, a 130-nm-thick Mg-doped p-type a-GaN layer was deposited. After the growth of the LED structure, the LED was activated at 725 °C in air ambient for 5 min by rapid thermal annealing. The hole concentration of the activated p-type a-GaN layer was 1.3 × 1018 cm−3 at room temperature. Conventional lateral LED devices with a size of 260 × 300 µm2 were fabricated. Figure 6
Fig. 6 Relative light output power and injection current of fabricated a-GaN LEDs in 10-80 mA range. The inset shows EL emission spectra and their FWHM at a current of 80 mA.
shows the dependences of the light output power of a-GaN LED devices as a function of injection current obtained by on-wafer measurements. The LED with the etched a-GaN layer had a much higher output power than the other LED devices. We attribute the high output power of the a-GaN LED to the etching process, which decreased the defect density and the density of nonradiative recombination centers in the MQWs, and increased light scattering by a number of nano- and microscale voids in the a-GaN layer. The inset in Fig. 6 shows the electroluminescence (EL) emission spectra of a-GaN LED devices at a current of 80 mA (100 A/cm2). The EL intensity of the etched a-GaN LED exhibits a high value with a narrow FWHM of 52 nm.

4. Conclusion

Nonpolar a-GaN layers with the low overall defect density were grown on r-plane sapphire substrates using a pulse NH3 interrupted etching process. During the regrowth of the etched a-GaN layer, a number of microscale voids were formed by the mass transport of GaN. The TD density was significantly reduced from that in the etched GaN area. LED device based on an a-GaN layer subjected to pulse NH3 interrupted etching had higher performance than a planar LED device owing to light scattering and the reduced number of nonradiative recombination centers in the MQWs.

References and links

1.

H. Amano, N. Sawaki, I. Akasaki, and Y. Toyoda, “Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer,” Appl. Phys. Lett. 48(5), 353–355 (1986). [CrossRef]

2.

S. Nakamura, S. Senoh, N. Iwasa, and S. Nagahama, “High-brightness InGaN blue, green and yellow light-emitting diodes with quantum well structures,” Jpn. J. Appl. Phys. Part 2 34(7A), L797–L799 (1995). [CrossRef]

3.

P. Waltereit, O. Brandt, A. Trampert, H. T. Grahn, J. Menniger, M. Ramsteiner, M. Reiche, and K. H. Ploog, “Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes,” Nature 406(6798), 865–868 (2000). [CrossRef] [PubMed]

4.

P. Lefebvre, A. Morel, M. Gallart, T. Taliercio, J. Allegre, B. Gil, H. Mathieu, B. Damilano, N. Grandjean, and J. Massies, “High internal electric field in a graded-width InGaN/GaN quantum well: accurate determination by time-resolved photoluminescence spectroscopy,” Appl. Phys. Lett. 78(9), 1252–1254 (2001). [CrossRef]

5.

T. Paskova, R. Kroeger, S. Figge, D. Hommel, V. Darakchieva, B. Monemar, E. Preble, A. Hanser, N. M. Williams, and M. Tutor, “High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire,” Appl. Phys. Lett. 89(5), 051914 (2006). [CrossRef]

6.

X. Ni, Ü. Özgür, H. Morkoç, Z. Liliental-Weber, and H. O. Everitt, “Epitaxial lateral overgrowth of a-plane GaN by metalorganic chemical vapor deposition,” J. Appl. Phys. 102(5), 053506 (2007). [CrossRef]

7.

T. Iwahashi, Y. Kitaoka, F. Kawamura, M. Yoshimura, Y. Mori, T. Sasaki, R. Armitage, and H. Hirayama, “Liquid phase epitaxy growth of m-plane GaN substrate using the Na flux method,” Jpn. J. Appl. Phys. 46(10), L227–L229 (2007). [CrossRef]

8.

D. Hanser, L. Liu, E. A. Preble, K. Udwary, T. Paskova, and K. R. Evans, “Fabrication and characterization of native non-polar GaN substrates,” J. Cryst. Growth 310(17), 3953–3956 (2008). [CrossRef]

9.

H. Yamada, Y. Iso, M. Saito, H. Hirasawa, N. Fellows, H. Masui, K. Fujito, J. S. Speck, S. P. DenBaars, and S. Nakamura, “Comparison of InGaN/GaN light emitting diodes grown on m-plnae and a-plane bulk GaN substrates,” Phys. Status Solidi 2, 89–91 (2008).

10.

C. Chen, J. Yang, H. Wang, J. Zhang, V. Adivarahan, M. Gaevski, E. Kuokstis, Z. Gong, M. Su, and M. A. Khan, “Lateral epitaxial overgrowth of fully coalesced a-plane GaN on r-plane sapphire,” Jpn. J. Appl. Phys. Part 2 42(6B), L640–L642 (2003). [CrossRef]

11.

S. M. Hwang, H. Y. Song, Y. G. Seo, J. S. Son, J. H. Kim, and K. H. Baik, “Enhanced electroluminescence of a-plane InGaN light emitting diodes grown on oxide-patterned r-plane sapphire substrates,” Opt. Express 19(23), 23036–23041 (2011). [CrossRef] [PubMed]

12.

J. S. Son, Y. Honda, M. Yamaguchi, H. Amano, K. H. Baik, Y. G. Seo, and S. M. Hwang, “Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates,” Thin Solid Films 546, 108–113 (2013). [CrossRef]

13.

J. L. Hollander, M. J. Kappers, C. McAleese, and C. J. Humphreys, “Improvements in a-plane GaN crystal quality by a two-step growth process,” Appl. Phys. Lett. 92(10), 101104 (2008). [CrossRef]

14.

J. S. Son, C. Miao, Y. Honda, M. Yamaguchi, H. Amano, Y. G. Seo, S. M. Hwang, and K. H. Baik, “Effects of nano- and microscale SiO2 masks on the growth of a-plane GaN layers on r-plane sapphire,” Jpn. J. Appl. Phys. 52(8S), 08JC04 (2013). [CrossRef]

15.

Z. A. Munir and A. W. Searcy, “Activation energy for the sublimation of gallium nitride,” J. Chem. Phys. 42(12), 4223–4228 (1965). [CrossRef]

16.

D. D. Koleske, A. E. Wickenden, R. L. Henry, J. C. Culbertson, and M. E. Twigg, “GaN decomposition in H2 and N2 at MOVPE temperatures and pressures,” J. Cryst. Growth 223(4), 466–483 (2001). [CrossRef]

17.

M. D. Craven, S. H. Lim, F. Wu, J. S. Speck, and S. P. DenBaars, “Structural characterization of nonpolar (11-20) a-plane GaN thin films grown on (1-102) r-plane sapphire,” Appl. Phys. Lett. 81(3), 469–471 (2002). [CrossRef]

18.

M. A. Moram, C. F. Johnston, J. L. Hollander, M. J. Kappers, and C. J. Humphreys, “Understanding x-ray diffraction of nonpolar gallium nitride films,” J. Appl. Phys. 105(11), 113501 (2009). [CrossRef]

19.

S. Nitta, M. Kariya, T. Kashima, S. Yamaguchi, H. Amano, and I. Akasaki, “Mass transport and reduction of threading dislocation in GaN,” Appl. Surf. Sci. 159–160, 421–426 (2000). [CrossRef]

20.

P. Vennéguès, B. Beaumont, V. Bousquet, M. Vaille, and P. Gibart, “Reduction mechanisms for defect densities in GaN using one- or two-step epitaxial lateral overgrowth methods,” J. Appl. Phys. 87(9), 4175–4181 (2000). [CrossRef]

21.

J. K. Sheu, S. J. Tu, M. L. Lee, Y. H. Yeh, C. C. Yang, F. W. Huang, W. C. Lai, C. W. Chen, and G. C. Chi, “Enhanced light output of GaN-based light-emitting diodes with embedded voids formed on Si-implanted GaN layers,” IEEE Electron Device Lett. 32(10), 1400–1402 (2011). [CrossRef]

22.

D. N. Zakharov, Z. Liliental-Weber, B. Wagner, Z. J. Reitmeier, E. A. Preble, and R. F. Davis, “Structural TEM study of nonpolar a-plane gallium nitride grown on (11-20) 4H-SiC by organometallic vapor phase epitaxy,” Phys. Rev. B 71(23), 235334 (2005). [CrossRef]

23.

H. Wang, C. Chen, Z. Gong, J. Zhang, M. Gaevski, M. Su, J. Yang, and M. A. Khan, “Anisotropic structural characteristics of (11-20) GaN templates and coalesced epitaxial lateral overgrown films deposited on (10-12) sapphire,” Appl. Phys. Lett. 84(4), 499–501 (2004). [CrossRef]

24.

K. Iso, H. Yamada, H. Hirasawa, N. Fellows, M. Saito, K. Fujito, S. P. Denbaars, J. S. Speck, and S. Nakamura, “High brightness blue InGaN/GaN light emitting diode on nonpolar m-plane bulk GaN substrate,” Jpn. J. Appl. Phys. 46(40), L960–L962 (2007). [CrossRef]

25.

A. Chitnis, C. Chen, V. Adivarahan, M. Shatalov, E. Kuokstis, V. Mandavilli, J. Yang, and M. A. Khan, “Visible light-emitting diodes using a-plane GaN-InGaN multiple quantum wells over r-plane sapphire,” Appl. Phys. Lett. 84(18), 3663 (2004). [CrossRef]

OCIS Codes
(230.0230) Optical devices : Optical devices
(230.3670) Optical devices : Light-emitting diodes

ToC Category:
Materials

History
Original Manuscript: December 16, 2013
Revised Manuscript: January 25, 2014
Manuscript Accepted: February 3, 2014
Published: February 6, 2014

Citation
Ji-Su Son, Yoshio Honda, and Hiroshi Amano, "Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH3 interrupted etching," Opt. Express 22, 3585-3592 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-3-3585


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References

  1. H. Amano, N. Sawaki, I. Akasaki, Y. Toyoda, “Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer,” Appl. Phys. Lett. 48(5), 353–355 (1986). [CrossRef]
  2. S. Nakamura, S. Senoh, N. Iwasa, S. Nagahama, “High-brightness InGaN blue, green and yellow light-emitting diodes with quantum well structures,” Jpn. J. Appl. Phys. Part 2 34(7A), L797–L799 (1995). [CrossRef]
  3. P. Waltereit, O. Brandt, A. Trampert, H. T. Grahn, J. Menniger, M. Ramsteiner, M. Reiche, K. H. Ploog, “Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes,” Nature 406(6798), 865–868 (2000). [CrossRef] [PubMed]
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