Positron annihilation study of magnetic elements doped GaN grown by molecular beam epitaxy

Yabuuchi, Atsushi*; Maekawa, Masaki; Kawasuso, Atsuo; Zhou, Y.*; Hasegawa, Shigehiko*; Asahi, Hajime*

Chromium-doped gallium nitride (GaCrN) has attracted much attention as a candidate material for spintronics devices. Two approaches have been utilized in improving the magnetization. Si-doping of GaCrN to enhance carrier-induced ferromagnetism and low temperature molecular beam epitaxy (MBE) growth to increase Cr atom concentration without formation of CrN precipitates. In this study, GaCrN films grown at high and low temperatures with and without Si-doping have been probed by a slow positron beam. As a result, no vacancy defects, which are larger than Ga vacancies, were detected in either the undoped or doped GaCrN films grown at 700C. In contrast, vacancy clusters with sizes of - were found to be responsible for positron trapping in undoped GaCrN films grown at 540C. Divacancies () were present in Si-doped GaCrN films grown at 540C, although vacancy clusters were eliminated by Si-doping.