Interaction of Hydrogen and Methane with Inp100) and GaAs(100) Surfaces

Abstract

The interaction of thermally activated hydrogen atoms and methane molecules with Inp100) and GaAs(100) surfaces was studied by X-ray and UV-induced photoelectron spectroscopy (XPS, UPS), high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and desorption spectroscopy (DS). In most cases the interaction causes a strong decomposition of the surface due to a preferential loss of the group-V and an enrichment of the group-III elements. Hydrogenation of the clean Inp100) 4×2 surface can be divided into three stages. First, there is a saturation of dangling bonds, where the 4×2 reconstruction is preserved. Then, there is a breaking of the In dimers present at the surface, resulting in a 4×1 LEED structure. Finally, a loss of phosphorus and the build-up of metallic indium droplets follows. Bombardment of Inp100) surfaces with methane ions results in the formation of In–C and P–C species. Hydrogen exposure of GaAs(100) surfaces is more effective, since it changes the surface structures already at the initial stages of interaction. This is corroborated by the HREELS and DS data, which give strong evidence for a preferential loss of arsenic. Desorption spectra were taken during the hydrogen exposure and they show for low hydrogen pressure directly the desorption of AsH3. For high hydrogen pressure (p ≥ 1×10−4 Torr) GaH3 is detected in addition. The intensity ratio of desorbing species (AsH3/GaH3) decreases with increasing hydrogen pressure. After extrapolation a value of one results at a pressure of p = 1×10−3 Torr. Models for the interaction of hydrogen and methane with Inp100) and GaAs(100) are discussed in detail.