Effect of nitrogen on the electronic band structure of group III-N-V alloys

We have studied optical transitions at the Γ and L points of the Brillouin zone of GaN_xAs_1-x and Al_y-Ga_1-yN_xAs_1-x alloys using photomodulation spectroscopy. For GaN_xAs_1-x with N contents between 0% and 2%, the N-induced shift of the conduction-band L minima is found to be only a fraction of the conduction-band edge shift at the Γ point. The measurements of Al_yGa_1-yN_xAs_1-x further show that there is no correlation between the location of the X conduction-band minima and the observed E₊ and E_- transitions. The results demonstrate that the N-induced interactions between extended Γ, L, and X conduction-band states do not play a significant role in modification of the conduction-band structure of III-N-V alloys. The N-induced change of the conduction-band structure is predominantly influenced by the anticrossing interaction between the extended states of the Γ conduction band and the localized states of nitrogen. ©2000 The American Physical Society.