Effect of annealing on the band bending and the overlayer morphology at Sb/III–V (110) interfaces

Abstract

The formation of the interface between Sb and GaAs(110) is studied for room temperature (RT) deposition and subsequent annealing using high-resolution soft X-ray photoemission spectroscopy (SXPS). The Sb 4d emission is found to consist of three spin-orbit doublets shifted in binding energy. Two components can be assigned to two inequivalent adsorption sites in the epitaxial Sb monolayer (ML). For coverages beyond 1 ML a third component develops which stems from the Sb in excess of the monolayer. Upon annealing above 500 K the Sb on top of the epitaxial monolayer desorbs completely leaving a well ordered monolayer behind. The changes in overlayer morphology are correlated with drastic changes in the Schottky barrier. Deposition up to 0.5 ML of Sb at RT causes a strong increase of the band bending on GaAs(110) or InP(110) substrates. In this coverage regime Schottky barriers of 0.5 eV on p-doped GaAs, 0.75 eV on n-doped GaAs and 0.75 eV on p-doped InP develop. The annealing reduces the barriers to 0.2 eV on p- and n-doped GaAs and 0.5 eV on p-doped InP. On p- and n-doped GaAs the Schottky barrier behaviour is correlated with dislocations and defects in the Sb monolayer, which on p-type GaAs were previously shown by STM spectroscopy to create electronic gap states. Upon annealing the dislocations are removed or reduced in density giving rise to a unpinning of the Fermi level. For Sb on InP(110), however, the results indicate that even after annealing donor type gap states exist with a sufficient density to pin the surface Fermi level.