Optical Properties of Substitutional Donors in ZnSe

Five substitutional donors have been observed in ZnSe: Al, Ga, In, Cl, and F. By measuring the $I_2$ lines and the two-electron transitions associated with each, the donor binding energies have been determined. These are found to be close to the effective-mass value and vary from 26.3 meV for Al to 29.3 meV for F. Excited states of the complex formed by the exciton bound to the neutral donor were observed both in the region above the $I_2$ lines and in the two-electron transitions. The electron effective mass was measured from the Zeeman splitting of the $2p$ states of the donors to be $m=(0.16\mathrm{}\pm 0.01)m_e$. For each donor, a doublet was also observed at lower energy than the $I_2$ lines; these doublets are believed to be the corresponding $I_3$ lines. The binding energies of excitons both to the ionized and the neutral donors were found to vary linearly with the donor central-cell correction. Most of these results are closely analogous to the properties of CdS and CdSe.