High-resolution photoemission study of hydrogen interaction with polar and nonpolar GaAs surfaces

We have used synchrotron-based high-resolution core-level photoemission and valence-band emission measurements to characterize hydrogen chemisorption on nonpolar GaAs(110) and polar GaAs(100) and GaAs(001) surfaces. Chemisorbed atomic hydrogen forms both Ga-H and As-H bonds on all three surfaces, causing chemical shifts of core-level binding energies and changing the valence-band emission. For low hydrogen exposures arsenic desorbs from all surfaces. However, at higher exposures, the (110) surface transforms into a Ga-rich structure with traces of metallic Ga, while the (100) surface transforms into an As-rich structure. We have also observed some additional changes in the binding energy of bulk components of Ga and As core levels as a function of hydrogen exposure, which may be explained by hydrogen-induced changes in band bending.