Selective Photon-Stimulated Desorption of Hydrogen from GaAs Surfaces

Photon-stimulated desorption of $\mathrm{H}{}^{+}$ from hydrogenated GaAs (110) and (100) surfaces was studied as a function of photon energy. Distinct peaks, observed around As $3d$ core-level binding energy for desorption from the GaAs (100) surface and in the As $3d$ and Ga $3p$ region for desorption from the GaAs (110) surface, show a striking similarity with the fine structure (spin-orbit splitting) measured in the photoemission from As $3d$ and Ga $3p$ levels. These results provide clear evidence for direct desorption processes and represent a basis for selective modification of hydrogenated GaAs surfaces.