Low-temperature photo-acoustic spectra of p-GaSe

The photo-acoustic spectra of p-GaSe were obtained below room temperature by using a ZnO transducer as a detector. Two peaks at 2.098 and 2.059 eV were observed at 99K. The energy and temperature variation of the 2.098 eV peak are well interpreted in terms of a free exciton annihilation. The peak at 2.059 eV is due to transitions from the donor level to the valence band.