Stress analysis of AlxGa1 xN films with microcracks

Thick Al x Ga 1 x N epilayer with microcracks grown by metalorganic vapor phase epitaxy on a GaN buffer above a 0001 sapphire substrate was comprehensively characterized by spatially and spectrally resolved cathodoluminescence CL and micro Raman spectroscopy. The variation of the CL line shift and the micro Raman measurements between the cracks are consistent with the interpretation that AlGaN is to a large extent stressed like a two dimensiional film between the microcracks with nearly full relaxation close to the cracks. A satisfactory theoretical confirmation of the stress distribution was obtained by a three dimensional finite element application of the elasticity theor