HIGHLY TUNABLE VALENCE-BAND OFFSET AT THE (111)SI SI HOMOJUNCTION VIAA CAF MONOLAYER SATURATED WITH H/

The possibility of modifying the band lineup at semiconductor heteroju nctions by deposition of intralayers of different materials is becomin g a tool in ''band engineering.'' It was found that CaF2, when inserte d between Si(111) and alpha-Si, generates a huge band offset. We prese nt first-principles calculations for a similar system, where alpha-Si is replaced by crystalline Si, and the dangling bonds are saturated wi th H, in two different structural morphologies, with an abrupt interfa ce configuration. We vary the width of the Si bulk layer and relax the positions of the interface atoms. Our results indicate the strong sen sitivity of the offset to the interface geometry: the potential lineup varies by as much as 1.5 eV as the interface atoms are relaxed to the ir equilibrium positions or the interface morphology is changed.