Electronic defect states of amorphous silicon nitride

The theoretical tight-binding/cluster-Bethe-lattice method is used to study the electronic states induced by the local bonding structures in amorphous silicon nitride. The electronic density of states of the clusters containing various bonding structures are calculated. The Si dangling bond (DB) can create a deep defect states in the gap. The N DB can induce a state below the top of the valence band. The Si-Si bond induces electronic states near the top of the valence band. For the N-N bond, there is an anti-bonding pπ* state near the valence band edge and an anti-bonding pσ* state in the energy gap. The SiH and NH bonds do not introduce defect states in the energy gap. They can give energy disorder to the band edges and contribute to the potential fluctuations. The N site of the Si 2 NH 2 complex can be positively charged and form a defect pair with the negatively charged Si DB. The Si 2 NH 2 complex can be a precursor for the charged N DBs before annealing.