Optical properties of GaSe grown with an excess and a lack of Ga atoms

Measurements of the photoluminescence (PL) and photocurrent (PC) have been made on GaSe with excess Ga or Se atoms. The 1.77 eV emission band for the sample with excess Ga atoms is attributed to the transition from the donor level at 0.175 eV to the acceptor level at 0.152 eV. This donor level is considered to be related to the defects formed by the interstitial Ga atoms. The 1.92 eV peak in the PC spectrum of the sample with excess Se atoms is thought to be associated with the interstitial Se atoms. Moreover, an emission band at 2.036 eV (PL spectra at 77 K) and a shoulder at 1.99 eV (PC spectra at 295 K) related to the indirect band transition were observed in the samples with excess Ga or Se atoms. It was found that the indirect band transition in GaSe is caused by the excess Ga and Se atoms. (C) 2003 American Institute of Physics.