Origin of the nitrogen-induced optical transitions in GaAs1-xNx -: art. no. 075207

The temperature and concentration dependence of optical transitions in GaAs1-xNx (<3.8 eV) are studied by electromodulated reflectance. These studies suggest that the E+ transition involves the valence-band maximum at Gamma and a singlet state originating from the splitting of the quadruply degenerate conduction band at L. Such a transition, forbidden in pure GaAs, becomes allowed in GaAs1-xNx due to the strong perturbation of nitrogen doping to the band structure. A similar analysis applied to the transition E-* suggests that it is related either to resonant states evolving from the level created by a single isolated nitrogen impurity in GaAs, or to the splitting of the triplet originating from the L conduction band, induced by a further reduction in symmetry associated with nitrogen pairs.