Influence of nitrogen resonant states on the electronic structure of GaNxAs1−x

We show using an sp3s∗ tight-binding Hamiltonian that replacing a single As atom by N introduces a resonant ‘impurity’ level above the conduction band edge in GaAs, and demonstrate that the interaction of this level with the conduction band edge accounts for the strong band gap bowing observed in GaNxAs1−x. We explicitly identify and track the resonant level even to alloy compositions as large as x=0.25. The conduction band edge energy can be described analytically assuming independent resonant states up to x∼0.03, but interactions between neighbouring resonances must be included for larger x. The model introduced here is not unique to GaNAs, but can be applied to describe conduction band bowing in any tetrahedrally bonded semiconductor alloy.