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Abstract: The effect of misorientation of 6H–SiC substrate on the structural quality of GaN epilayer grown by organometallic vapor phase epitaxy (MOVPE) has been investigated. The results reveal that the structural quality of GaN epilayer is significantly influenced by the misorientation of 6H–SiC substrate. Larger misorientation angle of 6H–SiC substrate results in better structural quality of GaN epilayer, such as narrower atomic step widths of GaN surface, less yellow luminescence band/edge emission (I y /I b ) ratio of PL, and lower dislocations density. It is also found that the I y /I b ratio of GaN epilayer is affected only by the misorientation angle of 6H–SiC substrate, but the screw dislocation density and edge dislocation density are influenced by both the misorientation angle and the misorientation direction of 6H–SiC substrate. GaN epilayer grown on 6H–SiC substrate with 2.3° misorientation angle towards direction has the best structural quality. [Copyright &y& Elsevier]

Abstract: The influence of AlN buffer growth temperature on the quality and stress of 4.5μm GaN epilayer on 6H–SiC substrate by organometallic vapor phase epitaxy (MOVPE) has been investigated. The crystalline quality and the atomic surface morphology were improved, the density of the pits and the stress of the GaN epilayer were reduced by increasing the growth temperature of the AlN buffer in the range from 950°C to 1100°C. By employing the optimized 1100°C growth temperature of AlN buffer, very high quality of GaN epilayer was achieved. The X-ray full width of half maximums (FWHMs) of (002) and (102) reflection rocking curves of the GaN epilayer have been improved to 159arcsec and 194arcsec, respectively, and the surface RMS to only 0.31nm in the 5μm×5μm atomic force microscopy (AFM) scan. The stress of GaN epilayer was investigated by X-ray diffraction and Raman scattering as well. The degree of the tensile stress in GaN epilayer could be suppressed by increasing the growth temperature of AlN buffer. Finally, a high quality of crack-free 4.5μm thick GaN epilayer was obtained on 6H–SiC substrate using the optimized 1100°C AlN growth temperature. [Copyright &y& Elsevier]

Abstract: In this paper, GaN films were successfully grown on the samples of MOCVD-GaN/Al2O3 (MGA) and MOCVD-GaN/6H-SiC (MGS) by HVPE method. We compare the strain of GaN films grown on the two samples by employing various characterization techniques. The surface morphology of GaN films were characterized by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The variations of strain characteristic were also microscopically identified using the Z scan of Raman spectroscopy. The Raman peak (E2) shift indicates that the stress enhanced gradually as a function of increasing the measurement depth. The strain of GaN grown on MGA sample is compressive strain, while on MGS is tensile strain. The stress of GaN films grown on MGA and MGS sample are calculated. The difference in the value of stress between calculation and measurement was interpreted. [Copyright &y& Elsevier]

Abstract: The influence of GaCl carrier gas flow rate on GaN films grown by hydride vapor-phase epitaxy (HVPE) was investigated. The symmetric (0002) and asymmetric (10–12) ω scans were detected to estimate the quality of GaN films. Optical properties were studied by room temperature photoluminescence spectra. Raman spectroscopy was employed to analyze the residual stress in the samples. The surface morphology of the GaN films was investigated by atomic force microscopy (AFM). On the basis of process optimization the optimal GaCl carrier gas flow rate for growth of high quality GaN films in our system was obtained as 1.3L/min. [Copyright &y& Elsevier]