Ab initiocluster calculations of hydrogenated GaAs(001) surfaces

Abstract

Hydrogen adsorption on the (2\ifmmode\times\else\texttimes\fi{}4) and (4\ifmmode\times\else\texttimes\fi{}2) reconstructions of gallium arsenide (001) has been studied by internal reflectance infrared spectroscopy and ab initio cluster calculations with density-functional theory. The calculations are made on ${\mathrm{Ga}}_{5}{\mathrm{As}}_{4}{\mathrm{H}}_{11,13},$ ${\mathrm{Ga}}_{4}{\mathrm{As}}_{5}{\mathrm{H}}_{11,13},$ and ${\mathrm{Ga}}_{7}{\mathrm{As}}_{8}{\mathrm{H}}_{19}$ clusters, which model the arsenic- and gallium-dimer termination of the semiconductor surface. Excellent agreement has been achieved between the vibrational frequencies predicted by the theory and those observed in experiments. On the (2\ifmmode\times\else\texttimes\fi{}4), hydrogen adsorbs on arsenic dimers to form isolated and coupled arsenic-monohydrogen bonds, and arsenic-dihydrogen bonds. Conversely, on the (4\ifmmode\times\else\texttimes\fi{}2), hydrogen adsorbs on gallium dimers to form terminal and bridged gallium hydrides. The latter species occur in isolated or coupled structures involving two or three Ga atoms.