INTERACTION OF HYDROGEN AND METHANE WITH INP(100) AND GAAS(100) SURFACES

The interaction of thermally activated hydrogen atoms and methane mole cules with InP(100) and GaAs(100) surfaces was studied by X-ray and UV -induced photoelectron spectroscopy (XPS, UPS), high resolution electr on energy loss spectroscopy (HREELS), low energy electron diffraction (LEED), scanning electron microscopy (SEM), energy dispersive X-ray sp ectroscopy (EDX) and desorption spectroscopy (DS). In most cases the i nteraction causes a strong decomposition of the surface due to a prefe rential loss of the group-V and an enrichment of the group-III element s. Hydrogenation of the clean InP(100) 4 x 2 surface can be divided in to three stages. First, there is a saturation of dangling bonds, where the 4 x 2 reconstruction is preserved. Then, there is a breaking of t he In dimers present at the surface, resulting in a 4 x 1 LEED structu re. Finally, a loss of phosphorus and the build-up of metallic indium droplets follows. Bombardment of InP(100) surfaces with methane ions r esults in the formation of In-C and P-C species. Hydrogen exposure of GaAs(100) surfaces is more effective, since it changes the surface str uctures already at the initial stages of interaction. This is corrobor ated by the HREELS and DS data, which give strong evidence for a prefe rential loss of arsenic. Desorption spectra were taken during the hydr ogen exposure and they show for low hydrogen pressure directly the des orption of AsH3. For high hydrogen pressure (p greater than or equal t o 1 x 10(-4) Torr) GaH3 is detected in addition. The intensity ratio o f desorbing species (AsH3/GaH3) decreases with increasing hydrogen pre ssure. After extrapolation a value of one results at a pressure of p = 1 x 10(-3) Torr. Models for the interaction of hydrogen and methane w ith InP(100) and GaAs(100) are discussed in detail.