Exchange electron-hole interaction at the isoelectronic oxygen trap in zinc selenide

We present photoluminescence (PL) and excitation data to show that oxygen substituting isoelectronically in ZnSe gives rise to a pair of transitions ${\mathit{A}}^{+}$(2.7895 eV) and B (2.7877 eV) as a result of the exchange interaction between the trapped electron-hole pair. The former is attributed to total angular momentum J=1, ${\mathrm{\ensuremath{\Gamma}}}_{4}$ representation, and is electric dipole allowed while the latter is assigned to J=2 belonging to the ${\mathrm{\ensuremath{\Gamma}}}_{3}$+${\mathrm{\ensuremath{\Gamma}}}_{5}$ representation and is electric dipole forbidden. Based on this model, we explain several experimental observations including varying PL intensity of the B line from sample to sample, the relatively rapid disappearance of the B line as a function of increasing temperature, and strong LO couplings of the ${\mathit{A}}^{+}$ and B lines.