Adsorption of chlorine and oxygen on cleaved InAs(110) surfaces: Raman spectroscopy, photoemission spectroscopy, and Kelvin probe measurements

Abstract

The interaction of Cl2 and of O2 molecules with cleaved InAs(110) surfaces was investigated at room temperature. Ultraviolet photoemission spectroscopy, a Kelvin probe, and electric-field-induced Raman spectroscopy were used to determine both the changes of surface band bending and of the ionization energy as a function of exposure to the molecules mentioned. Chlorine as well as oxygen are inducing depletion (inversion) and accumulation layers on samples doped p- and n-type, respectively. The Fermi level becomes finally pinned at 0.52 eV above the valence-band top for both adsorbates. This behavior indicates the presence of adsorbate-induced surface states of donor type at this energy position. With chlorine, an intermediate pinning position at 0.48 eV above the valence-band maximum, which is below the branch point of the virtual gap states of the complex InAs band structure, is observed. This result suggests that chlorine induces surface states of acceptor character on InAs(110) surfaces as is observed with GaAs(110) as well as InP(110) surfaces. Electric-field-induced Raman scattering has proven to be a very valuable tool for studies of accumulation layers.