Heterointerface formation of aluminum selenide with silicon: Electronic and atomic structure of Si(111):AlSe

In this paper we present a new, stable, unreconstructed surface termination of silicon, Si(111):AlSe. The structure forms the interface layer when aluminum sesquiselenide (Al₂Se₃) is deposited on Si(111) by molecular beam epitaxy. The atomic structure of the interface layer was investigated using angle-resolved valence and core-level photoelectron spectroscopy and diffraction. The Al₂Se₃∕Si(111) interface forms an unreconstructed bilayer structure similar to GaSe-terminated Si, with Al directly above the top Si atom and Se over the hollow site, although the temperatures for bilayer formation and for Se re-evaporation from the film are higher for AlSe than for GaSe. In addition, the valence band structure shows that the AlSe bilayer electronically passivates the bulk Si, with all interface states lying within the bulk Si bands.