Significantly reduced in-plane tensile stress of GaN films grown on SiC substrates by using graded AlGaN buffer and SiNx interlayer

In this work, GaN films were grown on SiC substrates by metal-organic chemical vapor deposition. The influence of the growth temperature, thickness, and growth rate of graded AlGaN buffer on the stress state in the GaN films were investigated. We find that the in-plane tensile stress in the GaN film can be reduced from ∼0.58 to ∼0.16 GPa by the optimization of the growth parameters of the graded AlGaN buffer. Under the optimized growth parameters, the GaN film also possess the best crystalline quality, for which the full width at half maximum (FWHM) of (0002) and (101¯2) X-ray diffraction (XRD) rocking curves are 240 and 288 arcsec, respectively. Based on the optimized growth parameters of the graded AlGaN buffer, the SiNx interlayer with a deposition time of 180 s was employed in the growth processes of the GaN film. As a result, the in-plane tensile stress in the GaN film is reduced to a much smaller value, which is about 0.04 GPa, and the crystalline quality of the GaN are further improved, for which the FWHM of (0002) and (101¯2) XRD rocking curves are 98 and 128 arcsec, respectively.