RADIATIVE RECOMBINATION IN SLIGHTLY OFF-STOICHIOMETRIC HIGH-PURITY CADMIUM-SULFIDE

The luminescence of high-purify cadmium sulfide prepared by a new tech nique and containing excess cadmium in concentrations up to 10(17) cm( -3) was investigated at 4.2 K. A distinctive feature of the CdS materi al studied is strong luminescence associated with the A(Gamma(5)) Sing let and A(Gamma(6)) triplet excitons and their LO replicas. The I-2 em ission band is due to radiative dissociation of excitons bound to cadm ium interstitials. The ionization energy of Cd-i is found to be 32 meV . A fine structure of the 4.2-K edge-emission spectrum in the range 50 6-514 nm, attributable to the quantum-size effect on the energy of rad iative transitions in donor-acceptors pairs separated by 10-40 Angstro m, was observed for the first time.