Optical properties of the E0＋Δ0 energy level higher than the bandgap of GaAs studied by micro-photoluminescence technique

Abstract

Using micro-photoluminescence technique, we observed a new photoluminescence peak about 0.348eV above the bandgap of GaAs (E0). By analyzing its optical characteristics, we assigned this peak to the nonequilibrium luminescence emission from the E0＋Δ0 bandgap in semi-insulated GaAs, which was further verified by Raman results. The observed polarization, excitation power dependence and temperature dependence of the photoluminescence spectra from the E0＋Δ0 energy level were very similar to those from the E0 of GaAs. This mainly resulted from the common conduction band around Γ6 that was involved in the two optical transition processes, and indicated that the optical properties of bulk GaAs were mainly determined by the intrinsic properties of the conduction band. Our results demonstrated that the micro-photoluminescence technique is a powerful tool to investigate the high energy states above the fundamental bandgap in semiconductor materials.