Electronic structure of a hole-attractive neutral Cu-related complex-defect bound exciton at 2.345 eV in ZnTe

A detailed magnetooptical study of a Cu-related bound exciton (BE) at 2.345 eV (2K) in ZnTe is presented, for magnetic fields up to 10 T. The corresponding complex defect is found to be of trigonal symmetry, and also neutral, from the absence of thermalization in Zeeman transmission spectra of the BE line. It has been possible to fit the Zeeman data for the splitting of the BE line with a perturbation Hamiltonian considering both the electron-hole exchange interaction and the local strain field at the defect. It appears that the defect has a hole-attractive potential of a moderate strength, so that the angular momentum for the bound hole is not quenched. The local strain field has a compressive sign, which leaves a ‖J,$M_J$〉=‖(3/2),±(1/2)〉 hole state at lowest energy. The g factor of this hole state is evaluated as K=1.20±0.01, L=-0.31±0.01, to our knowledge the first direct experimental data for such a ‖(3/2),±(1/2)〉 hole state in a semiconductor. The electron of the BE is loosely bound, with a g value of $g_e$=-0.40 typical for shallow donors in ZnTe. The defect is tentatively identified as a trigonal ${\mathrm{Cu}}_{\mathrm{Zn}}$-${\mathrm{Cu}}_{\mathrm{i}}$ pair.