Reversible temperature-dependent Fermi-level movement for metal-GaAs(110) interfaces

This paper describes how temperature regulates the movement of the surface Fermi level for lightly doped GaAs(110) onto which submonolayer amounts of Ti and Ag have been deposited. Synchrotron radiation photoemission spectra show that $E_F$ can be moved from near the band edges to ∼600 meV into the gap for p- and n-type GaAs by changing temperature from 20 to 300 K. Band bending changes are shown to be reversible when there are no morphology changes (Ti), but are not completely reversible when clustering occurs during the thermal cycle (Ag). These results demonstrate that the existence of gap states is not sufficient in itself to induce full band bending because charge exchange with those states is needed. They are discussed in the context of our dynamic-coupling model which shows how surface-bulk coupling is controlled by the bulk dopant concentration and temperature.