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

We show using an sp(3)s* tight-binding Hamiltonian that replacing a single As atom by N introduces a resonant 'impurity' level above the conduction ba nd edge in GaAs, and demonstrate that the interaction of this level with th e conduction band edge accounts for the strong band gap bowing observed in GaNxAs1-x. We explicitly identify and track the resonant level even to allo y compositions as large as x = 0.25. The conduction band edge energy can be described analytically assuming independent resonant states up to x simila r to 0.03, but interactions between neighbouring resonances must be include d for larger x. The model introduced here is not unique to GaNAs, but can b e applied to describe conduction band bowing in any tetrahedrally bonded se miconductor alloy. (C) 2001 Elsevier Science Ltd. All rights reserved.