Articles you may be interested inTwodimensional bulk bands and surface resonances originated from (100) surfaces of III-V semiconductor compounds AIP Conf.The effects of sulfur passivation on liquid-phase-epitaxy-grown n-type InGaP and AlGaAs surfaces have been studied using x-ray photoelectron spectroscopy. The surfaces were simultaneously prepared through degreasing and the use of an aqueous ͑NH 4 ͒ 2 S x treatment in air. For InGaP, sulfur atoms initially reacted with both surface In and Ga atoms and reacted negligibly with P atoms. The band bending was reduced by 0.7 eV compared to a sputter-cleaned surface. Presumably, sulfur eliminated P-vacancy-related gap states by occupying P sites and forming In-S and Ga-S bonds. By postheat treatment at 180°C, S atoms were not removed from the surface and band bending was reduced further by 0.1 eV. For AlGaAs, S atoms initially reacted with Ga and As, but this treatment could not remove the Al oxide previously formed in the air. Postheat treatment at 180°C simply induced S redistribution from As to Ga and As desorption, which reduced the band bending by 0.3 eV compared to the sputter-cleaned surface-a result similar to that for GaAs.

A high resolution core level photoemission study on the metal contact formed on S-passivated n-InGaP(100) surface reveals that the species produced by the chemical reaction of the deposited metal atoms with the surface atoms induce the gap states responsible for the Fermi level movement. The initial sulfur passivation of n-InGaP(100) surface efficiently reduced the gap states within the band gap and flattened the band bending by 0.6 eV relative to the sputter-cleaned surface. When the metals such as Al(Au) are deposited on the S/InGaP(100) surface, it was found that the deposited Al(Au) reacted with monosulfides resulting in the Al-sulfide (the remaining defective In-polysulfides) which seem to be the origin of the gap states.

Articles you may be interested inUnpinned interface Fermi-level in Schottky contacts to n-GaAs capped with low-temperature-grown GaAs; experiments and modeling using defect state distributions It has been confirmed by high-resolution x-ray photoelectron spectroscopy that the Fermi level of K-contacted sulfur-passivated GaAs͑100͒ is not located at the Fermi level of the ideal Schottky contact and is pinned near the midgap, even though the initial S passivation removes the high density gap states. With K deposition the Fermi level moves to 0.5 eV above the valence band maximum for both n-and p-type surfaces. The interfacial chemical reaction shows the top As element preferentially reacts with deposited K, and the interface still has dominant Ga-S bondings. These results imply that although the reactive alkali metal such as K does not break Ga-S bondings, it induces the metallic state which pins the Fermi level at 0.5 eV above the valence band maximum.