Photoreflectance (PR) spectroscopy has been used to study the Fermi-level pinning position of chemically modified (100) GaAs surfaces. It is shown that there are two pinning positions for the unmodified (100) GaAs surface. For n-GaAs, the Fermi level pins near midgap, while for p-GaAs the Fermi level pins near the valence band. We used an Ar/Cl(2) plasma generated by an electron-cyclotron resonance (ECR) source and P2S5 chemical passivation to change the stoichiometry of the surface. We show that ECR etching makes the surface oxide As rich and that the Fermi-level position for this circumstance is near midgap. The P(2)S(5) passivation produces a thin Ga rich oxide which is observed to pin the Fermi-level near the valence band. These results allow us to relate the Fermi-level pinning position to the stoichiometry of the GaAs/oxide interface.
Proceedings Title: Proceedings of SPIE
Conference Dates: January 26, 1994
Conference Location: Los Angeles, CA
Conference Title: Spectroscopic Characterization Techniques for Semiconductor Technology V, Orest J. Glembocki, Editor May 1994, Semiconductor Device Characterization I
Pub Type: Conferences