Comparative high-resolution electron-energy-loss spectroscopy study of hydrogen adsorption on GaAs and InP (111) and (1¯ 1¯ 1¯) surfaces

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Abstract
The hydrogen adsorption on GaAs and InP surfaces has been studied by high-resolution electron-energy-loss spectroscopy (HREELS). The stretching vibration modes of Ga—H, As—H, In—H, and P—H bonds corresponding to different energy-loss peaks in the spectra are all observed. However, the As—H vibration mode is usually confused with a combination loss of the Ga—H stretch plus a Fuchs-Kliewer phonon. Distinguishing As—H from the ‘‘Ga—H+phonon’’ peak could be done by comparison of the relative intensities of the loss peaks. The experimental data of HREELS show that the bonding between the adsorbed hydrogen and the surface atoms is largely determined by the surface atomic structure and electron distribution. For the GaAs(111) surface, only surface Ga atoms bond with the hydrogen under low exposures, while at high exposures, both As—H and Ga—H bonds could be formed. On the InP(111) surface (which is treated by annealing under phosphorus pressure), in addition to the In—H bond the P—H bond is formed even at low exposures. Only the P—H loss peak could be seen on InP(1¯ 1¯ 1¯), which illustrates that such a surface is fully terminated with P atoms. In the case of forming facets on the (1¯ 1¯ 1¯) surface, both surface group-III and group-V atoms could be bonded to hydrogen.