Valence band offset in AlAs/GaAs heterojunctions and the empirical relation for band alignment

Abstract

The valence band offset in AlAs/GaAs heterojunctions is found to be 0.45±0.05 eV from analysis of charge transfer versus undoped spacer layer thickness. This result and several recent experiments on Al_xGa_1−xAs/GaAs heterojunctions indicate that the valence band offset is approximately linear in AlAs fraction x over the entire alloy composition range and more than twice the previously accepted value. The relation between heterojunction band offsets and Fermi level pinning for metals on semiconductors is discussed.