Electron paramagnetic resonance and photoluminescence studies of CdTe: Cl crystals submitted to heat treatment

This communication is related to Electron Paramagnetic Resonance (PL) studies of chlorine-doped CdTe crystals submitted to heat treatment, which should enhance the chlorine solubility in the substitutional Te site and lessen A-centre formation. The temperature ranges from 350 to 600°C with a Cd layer or 700°C with partial PCd pressure extending from 50 to 400 Torr. The main results are: (1) Heat treatment at 350 < T < 600°C induce a decrease of the EPR isotropic photosignal (g = 1.684) and the PL line D1 (recombination of excitons bound to neutral donors). In the same time, a broad PL line W (related to the compensating process) appears and dominates the PL spectrum for high temperature annealings. (2) Heat treatments at 700°C with various PCd pressures show that: for PdCd = 50 Torr, a new EPR signal (non-photosensitive isotropic line at g = 1.666) is detected with is correlated to an increase of the PL line D1; for PCd = 150, 400 Torr, no EPR signal is observed, and PL results are comparable to those obtained in 350–600°C heat treatments. (3) The PL spectra also present a weakly coupled line G, which seems to be independent of the annealings. These results are discussed in connection with electrical measurements.