Spatial stress distribution and optical properties of GaN films grown on convex shape-patterned sapphire substrate by metalorganic chemical vapor deposition

mu-Raman and mu-photoluminescence methods have been employed to investigate microscopic spatial stress distribution and optical properties of GaN films grown on the convex shape-patterned sapphire substrate (CSPSS). By comparison of the mu-Raman and mu-PL spectra, we found that significantly large difference, Delta sigma(xx) similar to 0.46 GPa, in biaxial compressive stress between the flat trench and convex regions in the side facet of the GaN film, around similar to 2 mu m below the surface whereas on the GaN surface, little difference with large residual stress was observed in both regions compared to those from the side facet. Temperature dependent and time-resolved photoluminescence spectra have shown that the GaN film grown on the CSPSS has improved crystal purity through the reduction of intrinsic point defects. (C) 2010 Elsevier B.V. All rights reserved.