Atomistic study of the structural and electronic properties of a-Si:H/c-Si interfaces

We investigate the structural and electronic properties of the interface between hydrogenated amorphous silicon (aSi:H) and crystalline silicon (cSi) by combining tight binding molecular dynamics and DFT ab initio electronic structure calculations. We focus on the cSi(100)(11)/aSi:H, cSi(100)(21)/aSi:H and cSi(111)/aSi:H interfaces, due to their technological relevance. The analysis of atomic rearrangements induced at the interface by the interaction between H and Si allowed us to identify the relevant steps that lead to the transformation from cSi(100)(11)/aSi:H to cSi(100)(2x1)/aSi:H. The interface electronic structure is found to be characterized by spatially localized midgap states. Through them we have identified the relevant atomic structures responsible for the interface defect states, namely: dangling bonds, H bridges, and strained bonds. Our analysis contributes to a better understanding of the role of such defects in cSi/ aSi:H interfaces.