Shallow defect states in hydrogenated amorphous silicon oxide

Abstract

The theoretical cluster-Bethe-lattice method is used in this study to investigate the shallow defect states in hydrogenated amorphous silicon oxide. The electronic density of states (DOS) for the SiO 2 Bethe lattice of various Si–O–Si angles, non-bridging oxygen Si–O , peroxyl radical Si–O–O , threefold coordinated O 3 and Si–H bonds are calculated. The variation of the Si–O–Si bond angle causes the bandgap fluctuation and induces tail states near the conduction band minimum. The Si–O and Si–O–O bonds introduce shallow defect states in the energy gap near the top of the valence band. The Si–H bond induces a defect state, in the energy gap near the conduction band minimum, in a-SiO x with high oxygen concentration, but not low oxygen concentration. The O 3 bond itself does not induce defect state in the energy gap. The O 3 +D − complex, formed by the O 3 and threefold coordinated silicon, induces shallow state in the energy gap near the conduction band minimum. This defect state can explain the energy shift of photoluminescence of a-SiO x :H under annealing.