Photoemission study of the development of the Ti/GaAs(110) interface

Abstract

Photoemission spectra of the Ga and As 3d core levels, the Ti 3p core levels, and the valence bands have been used to study the formation of the Ti/GaAs(110) interface. These results indicate that a multicomponent interfacial zone forms with reaction initiated at ultralow coverage and a rapid shift of ${E}_{F}$ as the Schottky barrier forms (core-level shift 625 meV). After the onset of reaction, the Ga 3d core level shifts continuously to lower binding energy with increasing coverage (total shift of 1.66 eV by \ensuremath{\approxeq}60 A\r{} Ti deposition). The As core-level profile indicates immediate reaction, the formation of two Ti---As bonding configurations at low coverage, and the appearance of another which persists to very high Ti coverage (\ensuremath{\ge}160 A\r{}) and is characteristic of a Ti-metal-rich environment. Core-level intensity profiles show preferential out-diffusion of As at every stage of interface formation. Core studies of the evolving Ti 3p emission show gradual convergence to bulk Ti as the overlayer becomes increasingly Ti rich. Likewise, valence-band studies reveal predominantly As-derived states below metal d states at ${E}_{F}$. Comparison to previous results for Cr, V, Ce, and Sm overlayers on GaAs shows parallel trends in interface formation with differences related to the metal overlayer.