Growth, chemical interaction, and Schottky-barrier formation of column-III metal overlayers on InP(110)

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Abstract
We report soft-x-ray valence-band and core-level photoemission studies of the growth and chemical reaction of column-III (Al, Ga, In, and Tl) overlayers on cleaved InP(110). We find that the deposition of submonolayer coverages of these metals leaves the valence-band spectra devoid of any structure other than that characteristic of the clean InP(110) surface. Strong bonding between the Al, Ga, or In adatoms relative to the bond between the adatoms and the substrate leads to cluster formation on the surface. Growth of a uniform overlayer cannot, however, be excluded for Tl. Core-level spectra of substrate atoms and overlayer atoms for Al and Ga interfaces clearly indicate a room-temperature exchange reaction accompanying the islanding of nonreacted metal. No indications of such a reaction are found for In and Tl. The trends of the reaction are in agreement with predictions of bulk thermodynamics. The overall trend in the growth mode agrees with the theoretical predictions of Zunger.