Pressure behavior of Te isoelectronic centers in ZnS:Te

ZnS:Te epilayers with Te concentration from 0.5% to 3.1% were studied by photoluminescence under hydrostatic pressure at 15 K. Two emission bands related to the isolated Te 1 and Te 2 pair isoelectronic centers were observed in the samples with Te concentrations of 0.5% and 0.65%. For the samples with Te concentrations of 1.4% and 3.1%, only the Te 2-related peak was observed. The pressure coefficients of all the Te 1-related bands were found to be unexpectedly much larger than that of the ZnS band gap. The pressure coefficients for all the Te 2-related bands are, however, rather smaller than that of ZnS band gap as usually observed. Analysis based on a Koster-Slater model indicates that an increase of the valence bandwidth with pressure is the main reason for the faster pressure shift of the Te 1 centers, and the huge difference in the pressure behavior of the Te 1 and Te 2 centers is due mainly to the difference in the pressure-induced enhancement of the impurity potential on the Te 1 and Te 2 centers. © 2002 American Institute of Physics