Initial oxidation and oxide/semiconductor interface formation on GaAs

Abstract

Evolution of the oxide/GaAs interface formation for both thermal and anodic oxides is presented. This is accomplished by examining ESCA profiles of 21–85 Å thick thermal and anodic oxides. The anodic oxide begins with a nucleation and growth process during which the As oxides are leached out leaving a continuous layer of Ga2O3. Oxide growth then proceeds by Ga and As diffusion to the surface where they oxidize leaving the inner layer of Ga2O3 unchanged. Thus the anodic oxide/GaAs interface is formed during the first 40 Å of oxide growth. During thermal oxidation both Ga2O3 and As2O3 are formed but the As2O3 evaporates rapidly leaving the Ga2O3. Once the Ga2O3 layer is formed, the As is excluded from entering the continuous Ga2O3 layer and collects at the oxide/GaAs interface. This occurs after about 40 Å of oxide growth.