Penetration of electronic perturbations of dilute nitrogen impurities deep into the conduction band of GaP_1−xN_x

The electronic structure consequences of the perturbations caused by dilute nitrogen impurities in GaP are studied by means of supercell calculations using a fully atomistic empirical pseudopotential method. We find that numerous localized states are introduced by a single N atom and N clusters, not only close to the band edge but also throughout the GaP conduction band, up to ∼1 eV above the conduction band edge. These localized states suggest an alternative interpretation for a previously puzzling observation of splitting of photoluminescence excitation intensity at the GaP Γ_1c energy into two features, one blueshifting and the other staying pinned in energy with increasing N concentration.