Photo-induced current transient spectroscopy and photoluminescence studies of defects in AgGa0.6In0.4Se2

Abstract

Defect levels in semi-insulating AgGa0.6In0.4Se2 crystals grown by the horizontal Bridgman technique and annealed in vacuum at 750 °C for 20 days have been characterized using photo-induced current transient spectroscopy (PICTS) and low-temperature photoluminescence (PL). PICTS measurements revealed four electron-related defects located at (0.027 ± 0.008), (0.051 ± 0.005), (0.31 ± 0.01) and (0.98 ± 0.01) eV and two hole-related defects at (0.040 ± 0.012) and (0.73 ± 0.02) eV. Free exciton (FE) and donor–acceptor pairs emissions were observed in low-temperature PL spectra. The defect levels measured from PICTS are consistent with those from PL. The compositional uniformity of the crystals was investigated by employing micro-PL mapping of FE at 77 K. The temperature coefficients of the band-gap energies were estimated and discussed.