Electronic structure of a-Si1−xNx:H and a-Ge1−xNx:H

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Abstract
The electronic density of states of silicon nitrogen and germanium nitrogen alloys are calculated for the whole range of N concentrations. Also calculated are the local density of states at Si (Ge) atoms, at N atoms, and at sites with several configurations of dangling bonds. As single-site effective-medium theories are not applicable to semiconducting amorphous alloys due to the low values of the average coordination number (3≤〈z〉≤4), we apply here a real-space renormalization formalism that produces accurate results with little computational effort. This formalism simultaneously includes diagonal and off-diagonal disorder, short-range order, and the charge-transfer effect. The results obtained here compare well with the experimental measurements.