Local stress analysis of epitaxial laterally-overgrown GaN

Three-dimensional stress distributions for two different samples of epitaxial laterally-overgrown GaN deposited on SiO2 masks were simulated by continuum elasticity theory using the finite-element method. The samples have patterned masks in the (1(1) over bar 00) and (11(2) over bar 0) orientations, respectively The results of the simulation compared quantitatively quite well with the stress distributions derived from micro-Raman measurements. This success depended on taking into account the existence of a string of voids in the samples that could be seen in the transmission electron microscope image. From the buffer layer towards the sample surface, the biaxial stress relaxes within a relatively short distance to a value that corresponds to a biaxially compressed film. This value persists until a short distance from the sample surface.