RBS/Channeling Studies of Swift Heavy Ion Irradiated GaN Layers

Epitaxial GaN layers grown by MOCVD on c-plane sapphire substrates were irradiated with 150 MeV Ag ions at a fluence of 5 x 10(12) ions/cm(2). Samples used in this study are 2 gm thick GaN layers, with and without a thin AlN cap-layer. Energy dependent RBS/Channeling measurements have been carried out on both irradiated and unirradiated samples for defects characterization. Observed results are compared and correlated with previous HRXRD, AFM and optical studies. The chi(min) values for unirradiated samples show very high value and the calculated defect densities are of the order of 10(10) cm(-2) as expected in these samples. Effects of irradiation on these samples are different as initial samples had different defect densities. Epitaxial reconstruction of GaN buffer layer has been attributed to the observed changes, which are generally grown to reduce the strain between GaN and Sapphire