Phosphorus and Arsenic Impurity Centers in ZnSe. II. Optical and Electrical Properties

ZnSe crystals containing phosphorus or arsenic which are grown under conditions enhancing their incorporation as uncompensated acceptors show broad luminescence bands in the red and infrared portions of the spectrum. Excitation bands are found which are resolved from the band-edge absorption. Infrared quenching of photoluminescence and photoconductivity identify the 1.91-eV luminescence of ZnSe: P as originating from the ${\mathrm{P}}_{\mathrm{Se}}$ center identified by EPR. The crystals behave electrically as high-resistivity material showing $p$-type conductivity in the dark at elevated temperatures. Photoconductivity at low temperatures is $n$ type and is sensitized by the ionized ${\mathrm{P}}_{\mathrm{Se}}$ acceptor. Configuration coordinate curves for the ground and excited states of the ${\mathrm{P}}_{\mathrm{Se}}$ center are derived which are consistent with the distortions from $T_d$ symmetry observed previously by EPR.