Photoluminescence features which lay more than 0.15eV below the band edge in the ZnxCd1-xTe crystals (where x was between 0 and 0.09) were studied at cryogenic temperatures. The same features that were observed in pure CdTe samples (that is, a defect band which lay 0.13 to 0.20eV below the band-gap energy, and a peak at 1.1eV) were observed in the alloys. In annealed samples, it was observed that the 1.1eV feature, which was attributed to Te vacancies, increased with fast cooling. Increased concentrations of Te vacancies were explained by the phase diagram of CdTe, which indicated that higher concentrations of excess Cd appeared in CdTe which was quenched from high temperatures. An absorption transition near to 1.1eV was also observed by using photothermal deflection spectroscopy. The phase shifts showed that the deep defect was a bulk effect rather than a surface effect. The well-defined absorption peak suggested that the states which contributed to the 1.1eV transition were both localized. The results also suggested that the defect band which lay 0.13eV below the band gap (1.48eV in CdTe) might also be related to Te vacancies. However, the fact that the ratio of the intensities of this defect band and of the 1.1eV feature was highly variable suggested that the relationship was not simple. It was concluded that the origin of the defect band and its phonon replicas remained controversial.

C.B.Davis, D.D.Allred, A.Reyes-Mena, J.González-Hernández, O.González, B.C.Hess, W.P.Allred: Physical Review B, 1993, 47[20], 13363-9