Micro-Raman spectroscopy is performed to characterize GaN films grown on the patterned sapphire (0001) fabricated by wet chemical etching. The stress distributions are characterized by the frequency shift in the micro-Raman spectroscopy measurements. Residual stress state and carrier concentration in the mesa and wing region are assessed. The wing region shows lower compressive stress and less carrier concentration in comparison with mesa region. That is due to the interactions between sapphires and GaN as the result of diffe-rences in the coefficients of thermal expansion are excluded in the wing region by adopting maskless periodically grooved sapphire
thus less compressive stress and lower background carrier concentration can be achieved by this method.
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