Silver Schottky diodes on Kelvin, AES and LEED characterized (100)surfaces of GaAs cleaned by ion bombardment

Abstract

Schottky contacts were produced by silver evaporation on GaAs surfaces cleaned by ion bombardment. The samples work function were measured before and after metal deposition with the Kelvin method in an experimental set up which allowed a topographical study and direct comparison between n and p types. Surfaces were controlled by AES and LEED. It was found that the Fermi level of all the surfaces was pinned in the midgap range and so there was, on both n and p types, an important surface barrier qV s whose value did not strongly depend on the surface preparations we used. The diodes we obtained also presented an important barrier φ B for both n and p types. So it was deduced that diode barriers corresponded to those that were created by surface states and that metal deposition did not noticeably modify these states. On the other hand, surface preparations played an important role in the electrical performances of the diodes. It was deduced then that ion bombardment deteriorated the first atomic layers of the semiconductor.