SURFACE AND CONTACT PROPERTIES OF GAAS OVERLAID BY SILVER

AN INVESTIGATION WAS MADE OF THE SCHOTTKY BARRIER FORMATIONON CLEAVED N- AND P-TYPE GAAS THROUGH SURFACE AND CONTACT MEASUREMENTS. THE METAL USED WAS SILVER. SURFACE STUDIES, PERFORMED USING THE KELVIN METHOD, HAVE REVEALED THAT PINNING OF THE FERMI LEVEL IS OBTAINED AT SUBMONOLAYER COVERAGE AND THAT SILVER DEPOSITION INDUCED MODIFICATIONS IN THE ELECTRONIC AFFINITY. AN ELECTRICAL STUDY OF THE CONTACTS SHOWED THAT DIFFUSION BARRIER EV//D IS IN THE 950-MEV RANGE FOR THE N TYPE AND IN THE 270-MEV RANGE FOR THE P TYPE. THE DIFFERENCE BETWEEN THE PINNING LEVELS OF N AND P TYPES FOR SUBMONOLAYER COVERAGE WAS FOUND TO BE EQUAL TO THAT FOR CONTACTS. IT IS DEDUCED THAT THE SCHOTTKY BARRIER IS ESTABLISHED AS SOON AS THE FIRST SILVER ATOMS ARE DEPOSITED. POSSIBLE CHARACTERISTICS WERE CALCULATED FOR SURFACE STATES (ASSUMED TO BE DISCRETE).