Short-range order, large-scale potential fluctuations, and photoluminescence in amorphous SiNx

Abstract

The short-range order and electron structure of amorphous silicon nitride SiNx (x<4/3) have been studied by a combination of methods including high-resolution X-ray photoelectron spectroscopy. Neither random bonding nor random mixture models can adequately describe the structure of this compound. An intermediate model is proposed, which assumes giant potential fluctuations for electrons and holes, caused by inhomogeneities in the local chemical composition. The characteristic scale of these fluctuations for both electrons and holes is about 1.5 eV. The photoluminescence in SiNx is interpreted in terms of the optical transitions between quantum states of amorphous silicon clusters.