Donor-acceptor pair recombination in gallium sulfide

Low temperature photoluminescence of GaS single crystals shows three broad emission bands below 2.4 eV. Temperature and excitation light intensity dep endencies of these bands reveal that all of them originate from close donor -acceptor pair recombination processes. Temperature dependence of the peak energies of two of these bands in the visible range follow, as expected, th e band gap energy shift of GaS. However, the temperature dependence of the peak energy of the third band in the near infrared shows complex behavior b y blueshifting at low temperatures followed by a redshift at intermediate t emperatures and a second blueshift close to room temperature, which could o nly be explained via a configuration coordinate model. A simple model calcu lation indicates that the recombination centers are most likely located at the nearest neighbor lattice or interstitial sites. (C) 2000 American Insti tute of Physics. [S0021- 8979(00)04724-1].