Molecular Beam Epitaxy on the (NH₄)₂S_x-Treated Surface of GaAs

Abstract

We have found that treatment with a solution of ammonium sulfide containing excess sulfur [(NH4) 2Sx] produced a stabilized surface of GaAs. The treated surface is covered with a monomolecular layer of sulfur, and oxygen atoms are prohibited from adsorbing chemically on this surface. We checked the durability of the treated surface to heat treatment to find that it was stable up to more than 500 °C. Epitaxial growth of an Al film was demonstrated on the (NH4) 2Sx-treated surface. The presence of sulfur atoms at the interface by this treatment was found to suppress the chemical reaction between the metal and GaAs. Low temperature GaAs epitaxy was demonstrated on the sulfide treated surface without conventional heat treatment. The surface treatment correlates with changes in Schottky barrier height with various metals, which suggests that the surface states of GaAs are decreased remarkably.