PHOTOELECTRON-SPECTROSCOPY STUDY OF GA 3D AND AS 3D CORE LEVELS ON MBE-GROWN GAAS-SURFACES

We have performed a photoemission study of GaAs MBE-grown surfaces, using UV radiation to investigate Ga3d core levels (CLs) of (100) and (111)B surfaces in-situ, and using synchrotron radiation ex-situ for the As3d and the Ga3d CLs study. Different reconstructions were studied, from the As-saturated to the Ga-stabilized ones, and we focused on the surface contributions. A surface signal attributed to Ga atoms on the surface was found even on c(4 x 4) surfaces, where it was not expected. The capping/decapping method was found a good way to investigate GaAs(100) surfaces ex-situ, but such surfaces were extremely sensitive to the decapping procedure. Finally, the surface Fermi level was measured on the (100) surfaces, and was always found pinned, regardless of the reconstruction.