Valley-Valley Splitting in Inversion Layers on a High-Index Surface of Silicon

The superlattice phenomenon observed by Cole, Lakhani, and Stiles in the electron inversion layer on (119)Si is explained by projecting the bulk band structure onto the surface. On high-index surfaces, the valley degeneracy only occurs at the surface-band-structure zone boundary. Lifting this degeneracy gives rise to minigaps which we observe in the optical conductivity as interband absorption.