Alloying induced shift between excitation and luminescence of the nitrogen bound exciton in GaPxAs1−x alloys

Photoluminescence and luminescence excitation spectra have been performed on epitaxial layers of nitrogen doped GaP_xAs_1?x alloys (x > 0.85). The main luminescence excitation band A appears above the photoluminescence band N_x. The composition dependence of this energy shift suggests an alloying energy shift. The origin of this new effect would be the thermalization of the bound exciton population to the lower energy states of the A absorption band which reflects the density of states broadening due to As-P disorder around N atoms