The effect of thermal neutron-induced damage on photoluminescence in CdTe

Abstract

The effects of lattice damage produced by prompt γ-induced Cd¹¹⁴ recoil on the photoluminescence at 9 K in CdTe have been studied. All the observed photoluminesccnce bands decreased in intensity after thermal neutron irradiation. Following exposure to large thermal neutron fluences the exciton recombination in both n- and p-type CdTe is dominated by two bound exciton bands at 1.574 eV and 1.589 eV. These bands are attributed to excitons trapped at native defect-associated acceptors. The edge emission in these crystals usually occurs as a doublet with the low energy member (donor-acceptor pair) dominant in n-type and the high energy member (free electron-to-bound hole) dominant in p-type. However, after irradiation the high energy peak is always dominant in both n- and p-type CdTe. This is attributed to an increase in the ratio of the number of native defect acceptors, common to both the low and high energy members, to the number of donors that participate in the low energy emission. Similar to the low energy edge emission, the 1.45 eV emission band, due to a native defect acceptor-donor complex, decreases following irradiation. These results can be interpreted on the basis of a recoil model in which Cd defects are produced at a greater rate than Te defects.