Photoemission studies of the GaAs-Cs interface

Abstract

Photoemission has been used to study changes in the electronic structure of the surface of GaAs as submonolayer quantities of Cs were added to the surface. The observed behavior has implications for the theory of the formation of Schottky barriers. As the Cs coverage was increased the Fermi-level pinning position of $p$-type GaAs was seen to rise to above midgap and then to move downward by about 0.2 eV. Also, as the Cs coverage was increased, states were seen to move up into the gap from the valence-band maximum. The results indicate that the empty surface states on the clean GaAs surface play a large role in determining the Fermi-level pinning position, but that other mechanisms also play a part.