Acceptor levels in GaSe:In crystals investigated by deep-level transient spectroscopy and photoluminescence

Deep-acceptor levels associated with indium in indium-doped GaSe crystals have been measured. High-quality Schottky diodes of GaSe:In have been fabricated and characterized using current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS). Four DLTS peaks at 127, 160, 248, and $319K$⁠, corresponding to 0.21, 0.22, 0.44, and $0.74eV$ above the valence band, were well resolved and assigned to be an indium-on-gallium antisite $(InGa)$⁠, a gallium vacancy $(VGa)$⁠, an indium gallium vacancy complex $(VGa-In)$⁠, and a native defect associated with stacking fault or dislocation, respectively. Low-temperature photoluminescence (PL) spectroscopy measure-ments were performed on GaSe and GaSe:In crystals. The ground and the first excited states of the free exciton emissions were identified and the band-gap energies were determined. The results that the peak of exciton bound to acceptor $(A0,X)$ disappeared and the peak of donor-acceptor pair appeared in GaSe crystal after indium doping are consistent with the DLTS acceptor assignments.