TEMPERATURE-DEPENDENT CHEMICAL AND ELECTRONIC-STRUCTURE OF RECONSTRUCTED GAAS (100) SURFACES

Low-energy electron diffraction, soft x-ray photoemission, cathodoluminescence (CL), and Auger electron spectroscopies have been performed to investigate the geometric, chemical, and electronic properties of GaAs (100) surfaces as a function of annealing temperature and surface reconstruction. These measurements indicate gradual changes in surface geometry, composition, deep level CL features, and Fermi-level (E(F)) position with increasing temperature of surface preparation. In contrast, it was observed that pronounced changes in the surface ionization potential and work function between different surface reconstructions. For most of the desorption temperatures and surface reconstructions, the secondary electron emission exhibits characteristic double onsets, possibly due to the existence of differently reconstructed patches on the surface. The implications of these variations in the surface chemical and electronic structure of GaAs (100) surfaces on their metal contact properties. It was concluded that (a) unique characterization of these surfaces requires measurements of geometric ordering, chemical composition and bonding, and deep level emission in the band gap, and (b) the correlation of the surface geometry with chemical and electronic surface and interface structure points to the central role of surface preparation in achieving controlled Schottky barrier behavior.