Growth temperature dependence of strain in a GaN epilayer, grown on a c-plane sapphire substrate

The growth temperature dependence of residual stress in a GaN epilayer grown on a c-plane sapphire substrate was analyzed. The c- and a-lattice parameters were measured using HRXRD, followed by the out-of-plane and in-plane strains. The unstrained c-lattice and a-lattice parameters obtained from a reference were used to measure the out-of plane and in-plane strain components. The highest growth temperature in the metalorganic chemical vapor deposition of GaN on c-plane sapphire was most effective in reducing the hydrostatic strain. The observation that the calculated value of thermal strain and the measured biaxial strain approach each other with increase in growth temperature shows that relaxation of any sort and growth stress contributions diminish with increasing growth temperatures.