Photoluminescence of Cd1—xZnxTe Crystals Grown by High-Pressure Bridgman Technique

Abstract

Photoluminescence (PL) spectra of detector-grade Cd1—xZnii xTe crystals with x = 0.07 to 0.14 were measured as a function of the excitation laser power and over the temperature range from 12 to 295 K. Two bound exciton transitions at the energies of 13 and 24 meV below the band-gap Eg and a number of phonon replicas dominate the low-temperature PL spectra. The transition at the energy of Eg — 13 meV is attributed to a neutral donor-bound exciton D0X. The excitation power and temperature dependence of the peak at the energy of Eg — 24 meV show that it is of excitonic origin with binding energy of 13 meV. The intensity of this A0X peak is found to depend on x, which suggests that it is related to structural defects. In some samples a donor–acceptor pair (DAP) transition at the energy of Eg – 60 meV is observed. The PL spectra also exhibit a weak, defect-related broad peak at the energy of about Eg — 200 meV. The PL of a large number of samples from different boules and locations in the boules is compared. The DAP-peak intensity was observed to depend strongly on the boule.