UPS and LEED studies of GaAs (110) and (111) As surfaces

Abstract

By comparison of LEED intensity–voltage data on GaAs (110) surfaces prepared by cleaving and by chemical etch followed by sputter annealing, we find the surfaces to be essentially the same in atomic geometry within the limits of experimental error. However, we find that important distinctions can be made between (110) surfaces prepared by these two methods when Fermi-energy pinning and UPS data are considered. In this regard, we show that Fermi-energy pinning is a particularly sensitive indicator of the degree of surface perfection and that the UPS data gives valuable information about the degree of perfection achieved by the different surface preparation techniques used. As an example of this, we show differences in the spatial distribution of damage on sputter-annealed and heat-cleaned surfaces which are seen by UPS. The sputtered surface is extremely imperfect prior to annealing. Finally, we find no evidence for intrinsic filled surface states in the band gap on the (111) As surface when prepared by heat cleaning or sputter annealing.