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 ${\mathrm{GaN}}_x{\mathrm{As}}_{1-x}$ and ${\mathrm{Al}}_y{\mathrm{Ga}}_{1-y}{\mathrm{N}}_x{\mathrm{As}}_{1-x}$ alloys using photomodulation spectroscopy. For ${\mathrm{GaN}}_x{\mathrm{As}}_{1-x}$ 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 ${\mathrm{Al}}_y{\mathrm{Ga}}_{1-y}{\mathrm{N}}_x{\mathrm{As}}_{1-x}$ 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.