Improvement of crystal quality HVPE grown GaN on an H3PO4 etched template

et al. 2015

Sci Rep

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In this work, high quality GaN crystal was successfully grown on C-face 6H-SiC by HVPE using a two steps growth process. Due to the small interaction stress between the GaN and the SiC substrate, the GaN was self-separated from the SiC substrate even with a small thickness of about 100 μm. Moreover, the SiC substrate was excellent without damage after the whole process so that it can be repeatedly used in the GaN growth. Hot phosphoric acid etching (at 240 °C for 30 min) was employed to identify the polarity of the GaN layer. According to the etching results, the obtained layer was Ga-polar GaN. High-resolution X-ray diffraction (HRXRD) and electron backscatter diffraction (EBSD) were done to characterize the quality of the freestanding GaN. The Raman measurements showed that the freestanding GaN film grown on the C-face 6H-SiC was stress-free. The optical properties of the freestanding GaN layer were determined by photoluminescence (PL) spectra.

contrasting

confidence: 90%

Direct growth of freestanding GaN on C-face SiC by HVPE

Tian

et al. 2015

Sci Rep

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“…This method of stress control is performed accurately not only with the two different templates examined in this study, but also in the case of templates with different types of stress cited in our previous work. 24,25…”

Section: Discussionmentioning

confidence: 99%

Influence of V/III ratio on stress control in GaN grown on different templates by hydride vapour phase epitaxy

Dai

et al. 2014

RSC Adv.

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GaN crystals were grown on MOCVD-GaN/Al 2 O 3 templates (MGA) and MOCVD-GaN/6H-SiC templates (MGS) in a hydride vapour phase epitaxy (HVPE) process where the V/III ratio was controlled. The tensile stress that exists in MGS was controlled by an increasing V/III ratio. The compressive stress that appears in MGA was controlled by a decreasing V/III ratio. The mechanism of stress control using the V/III ratio is discussed in terms of the interrelation of the stress, the V/III ratio and the crystal growth. The stress in these two kinds of substrates causes differences in atomic mobility which may be compensated by varying the V/III ratio. It is found that a larger V/III ratio results in a higher atomic mobility. Thus, atomic mobility is retarded by compressive stress and increased by tensile stress. This method of stress control has been shown to provide worthwhile guidance for GaN growth on different templates, and under different conditions in other investigations.

“…To reduce the residual stress and realize the self-separation of GaN crystals, our group has explored several methods, including wet chemical etching 19 , high temperature annealing 20 , 21 and electrochemical etching methods 22 , to fabricate the nanoporous GaN buffer layer. However, the wet chemical etching method and the high temperature annealing method cannot be well controlled because of the anisotropic chemical activity of GaN crystal 23 .…”

Section: Introductionmentioning

confidence: 99%

High quality self-separated GaN crystal grown on a novel nanoporous template by HVPE

Huo

et al. 2018

Sci Rep

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In this study, a novel nanoporous template was obtained by a two-step etching process from MOCVD-GaN/Al2O3 (MGA) with electrochemical etching sequentially followed by chemical wet etching. The twice-etched MOCVD-GaN/Al2O3 (TEMGA) templates were utilized to grow GaN crystals by hydride vapor phase epitaxy (HVPE) method. The GaN crystals were separated spontaneously from the TEMGA template with the assistance of voids formed by the etched nanopores. Several techniques were utilized to characterize the quality of the free-standing GaN crystals obtained from the TEMGA template. Results showed that the quality of the as-obtained GaN crystals was improved obviously compared with those grown on the MGA. This convenient technique can be applied to grow high-quality free-standing GaN crystals.