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 Te1 and Te2 pair iso-electronic 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 Te2-related peak was observed. The pressure coefficients of all the Te1-related bands were found to be unexpectedly much larger than that of the ZnS band-gap. The pressure coefficients for all the Te2-related bands are, however, rather smaller than that of ZnS band-gap as usually observed. Analysis based upon a Koster–Slater model indicated that an increase of the valence bandwidth with pressure was the main reason for the faster pressure shift of the Te1 centers, and the huge difference in the pressure behavior of the Te1 and Te2 centers was due mainly to the difference in the pressure-induced enhancement of the impurity potential on the Te1 and Te2 centers.

Pressure Behavior of Te Iso-Electronic Centers in ZnS:Te. Z.L.Fang, F.H.Su, B.S.Ma, K.Ding, H.X.Han, G.H.Li, I.K.Sou, W.K.Ge: Applied Physics Letters, 2002, 81[17], 3170-2