Silicon quantum well as passivation barrier on GaAs surface

Abstract

Synchrotron radiation Si L-edge absorption spectroscopy is used to study the band structure of thin silicon passivation films on GaAs(100) surface. The measurements show that the Si L-edge, which measures the conduction band minimum (CBM), is shifted drastically to a higher energy as the Si film thickness is reduced to below 2.5 nm. This shift in the CBM is found to scale with the Si layer thickness L as 1/L1.7, indicating that the electronic states within the Si layer are quantum confined. Within a confined quantum well, the energy levels of all states including localized gap states will be shifted to higher energy. Quantum confinement effects in the thin Si layer is found responsible for its successful use for passivation of GaAs surfaces.