Study of acceptor states in CdTe by donor-acceptor pair excitation luminescence

Excitation of donor-acceptor pair luminescence has been studied in CdTe doped with lithium or chlorine. The excitation spectrum of the lithium acceptor is determined and fitted with the effective mass theory of Baldereschi and Lipari. Revised values of the valence band parameters are deduced: μ = 0.8, δ = 0.054, Ry = 24 meV. The analysis of the 1.45 eV luminescence band in compensated Cl-doped crystals shows the existence of donor-acceptor pair transitions. Three acceptor centers are identified: E_A = 89, 111 and 119 meV, and the contribution of a deep donor (E_D > 40 meV) is demonstrated. Besides intracentre type excitation transitions of the 1.45 eV band have been observed in non-compensated chlorine-doped crystals. Thus several recombination channels and distinct acceptor states contribute to the composite 1.45 eV luminescence band.