Effects of electron cyclotron resonance etching on the ambient (100) GaAs surface

Photoreflectance has been used to study the electronic behavior of the ambient (100) GaAs surface and its modification by etching in a Cl ₂/Ar plasma generated by an electron-cyclotron resonance (ECR) source. We observed two pinning positions for ambient (100) GaAs, with n-GaAs pinning near midgap and p-GaAs pinning near the valance band. ECR etching shifts the Fermi level of p-GaAs toward midgap, but has little effect on n-GaAs. The surface modification is most influenced by the rf power. Auger electron spectroscopy indicates that the etching increases As at the GaAs/oxide interface. We suggest that the Ga/As ratio controls the position of the Fermi level.© 1995 American Institute of Physics.