Optically-detected magnetic resonance of excitons bound at Te2 isoelectronic centres in CdS1-xTex

The first ODMR experiments on excitons bound at isoelectronic traps in a II-VI semiconductor are reported. In CdS1-xTex with x ∼ 0.02, recombination emission is obtained at 700 nm from excitons bound at Te2 pairs. The ODMR spectra obtained by monitoring polarization changes in this emission shows that the recombination occurs from a triplet state, thus confirming that the number of bound particles in the exciton is two. The symmetry of the ODMR spectra is related to the Te2 pair orientation and this, together with the spin-Hamiltonian parameters, is consistent with the strong binding postulated for the hole in such an exciton. The additional observation of ODMR signals from shallow neutral donors is taken as evidence for efficient energy transfer between donor-acceptor pairs and the excitons bound at the Te2 centres. (author)