Ultraviolet photoelectron spectroscopy investigation of electron affinity and polarity on a cylindrical GaAs single crystal

Abstract

The orientation dependence of the electron affinity $\chi$ was measured by ultraviolet photoelectron spectroscopy on the surface of a cylindrically shaped GaAs crystal with [$1\overline{1}0$] as its axis, prepared by ion bombardment without and with annealing as well as molecular-beam epitaxy. The polarity of GaAs and thus surface stoichiometry and relaxation give the main contribution to the variation of $\chi$. Ga(As) turns out to be positively (negatively) charged. The results are consistent with a reduced charge on the surface atoms compared to the bulk.