Effects of Zn-vapor heat treatments on the edge emission and deep-center luminescence of ZnTe

Abstract

Using cathodoluminescence measurements at 80–300K, we have investigated the effects of Zn-vapor heat treatments on the injection level dependence, frequency response, and temperature dependence of the edge emission and the extrinsic deepcenter luminescence of vapor-phase-grown ZnTe. The results are compared to those from the same material in its as-grown condition. Zn-vapor heat treatments greatly enhance the 1.8 eV deep-center band and make it the dominant spectral feature at all temperatures investigated. The resulting band shows little change in shape or energy with injection level, and the temperature dependence of the band does not suggest thermal exchange between a participating energy level and a band edge. While the energy of the 1.8 eV band does decrease with increasing temperature, it does not match the variation of the band gap with temperature. It is found that the 1.8 eV band broadens with increasing temperature in a way satisfactorily explained by configurationcoordinate modeling. The kinetics of the 1.8 eV band show complex detail, both at 80K and 300K, but microsecond-magnitude exponential components are dominant. In contrast, the kinetics of the edge emission are much faster. However, despite the difference in kinetics, the intensities of the 1.8 eV band and the edge emission at 80K scale closely with each other over a wide range of injection levels. This remarkable result indicates that the edge emission and deep-center luminescence processes do not involve independent competition for injected carriers in Zn-fired ZnTe.