First-principles study of initial growth of GaXO layer on GaAs-β2(2×4) surface and interface passivation by F

Abstract

A theoretical scheme is used to investigate atomic and electronic structures of the growth of gallium oxides on the GaAs(001) surface and Ga XO/GaAs interface. Using first principles molecular dynamics, it is found that oxygen and surface As-As dimer have a mutual diffusion when Ga 2O3 molecular species gradually precipitate on the GaAs(001)-2(2 4) surface until the surface is fully covered by one monolayer. One Ga-Ga dimer and a Ga atom with low coordination are observed. These bondings lead to gap states located in the upper half region of the GaAs bandgap. Further partial charge analysis shows that these gap states arise from Ga-dangling bonds and the low-coordinated Ga atoms which are removed by the subsequent Ga2O growth. Moreover, further Ga2O growth results in the formation of unsaturated As-O. Consequently, gap states are introduced in the lower part of the GaAs gap. In both cases, F assists in eliminating unsaturated Ga- or As-related bonds and shows a significant passivation effect, i.e., removing the gap states. © 2011 American Institute of Physics.