Electronic structure of a neutral Cu-related complex defect with a bound exciton at 2.3296 eV in ZnTe.

Abstract

A complex defect with a bound exciton (BE) at 2.3296 eV (at 2 K) in Cu-diffused ZnTe is studied in detail with laser spectroscopy, including magneto-optical measurements in fields up to 10 T. The defect is found to be axial and (110)-oriented, suggesting a substitutional pair ${\mathrm{Cu}}_{\mathrm{Zn}}$-${D}_{\mathrm{Zn}}$ as the identity, where ${D}_{\mathrm{Zn}}$ is a shallow donor on a Zn site. This suggestion is consistent with the fact that the defect is neutral, from the absence of thermalization in Zeeman transmission data. The Zeeman data can be fitted with a spin Hamiltonian dominated by a rather strong tensional local strain field, with a small electron-hole exchange interaction (\ensuremath{\approxeq}0.02 meV). The defect has a moderately strong hole-attractive local potential, presumably due to ${\mathrm{Cu}}_{\mathrm{Zn}}$, and the angular momentum for the bound hole is not quenched. The tensional sign of the local strain field leaves a \ensuremath{\Vert}J,${M}_{J}$〉=\ensuremath{\Vert}(3/2,\ifmmode\pm\else\textpm\fi{} 3) / 2 〉 doublet as the lowest hole state, with a hole g factor given by K=1.25\ifmmode\pm\else\textpm\fi{}0.02, L=-0.21\ifmmode\pm\else\textpm\fi{}0.01. The electron in this BE is loosely bound as a secondary particle, with an isotropic g value ${g}_{e}$=-0.38\ifmmode\pm\else\textpm\fi{}0.02, quite similar to the value ${g}_{e}$=-0.40 for shallow donors in ZnTe.