Electron energy loss spectroscopy and work function measurements on Sb/GaAs(110): Example of an unpinned interface?

Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), and contact potential difference (CPD) measurements are performed on Sb overlayers deposited on room temperature and low temperature n-type GaAs(110) surfaces. In agreement with earlier LEED results, AES indicates a Stranski-Krastanov growth mode at room temperature with 3-D nucleation on top of an atomically ordered Sb monolayer (ML). The changes in the GaAs surface exciton amplitude and surface plasm on energy also show the growth of an epitaxial monolayer which suppresses the substrate surface relaxation. Work function and surface photovoltage measurements performed during deposition of Sb on the room temperature substrate show that the band bending at the GaAs(110) surface first increases as a function of Sb coverage and then decreases to a very small value when the coverage reaches 1 ML. This suggests that, with a 1 ML coverage, the density of deep acceptor states due to Sb induced defects, atomic reconstruction or chemical bonds, is considerably smaller than the density of states which pin the Fermi level at other metal-GaAs interfaces.