Depth dependence of defect density and stress in GaN grown on SiC

Abstract

We report high resolution x-ray diffraction studies of the relaxation of elastic strain in GaN grown on SiC(0001). The GaN layers were grown with thickness ranging from 0.29to30μm. High level of residual elastic strain was found in thin (0.29to0.73μm thick) GaN layers. This correlates with low density of threading screw dislocations of 1-2×107cm−2, observed in a surface layer formed over a defective nucleation layer. Stress was found to be very close to what is expected from thermal expansion mismatch between the GaN and SiC. A model based on generation and diffusion of point defects accounts for these observations.