Band gap energy, nitrogen localized states and GaN-like phonon in heavily doped GaAsN grown by molecular beam epitaxy

We have performed spectroscopic measurements in order to investigate the exciton localization mechanism in GaAs heavily doped with nitrogen. At low nitrogen content, corresponding to 5×1018 cm−3, the low temperature photoluminescence spectra are governed by several features of excitons bound to nitrogen complexes. In the case where the nitrogen content reaches 8×1019 cm−3, these bound states are tightly coupled to form a wide band below the GaAsN bandgap energy. We have used the Bose–Einstein expression to interpret the temperature dependence of the bandgap energy, taking into account the exciton–phonon interaction. We have found that the interaction between exciton localized at nitrogen complexes and the localized Ga–N vibration mode plays an important role in the reduction of the temperature dependence of the heavily doped GaAsN bandgap energy.