Cleaved surfaces of indium phosphide and their interfaces with metal electrodes

Abstract

The electronic structure of atomically clean cleaved (110) surfaces of InP has been investigated for a range of crystals of different doping. The Fermi level at the surface is not clamped by surface states. The chemical nature of clean and contaminated (110) surfaces have been investigated and interfaces between them and metal contacts examined by a range of techniques including a novel ultra-high-vacuum scratch test method. Whereas indium forms ohmic contacts to all faces studied, gold and silver form Schottky barriers which are nearly identical in magnitude. These barriers are of practically the same magnitude for intimate (clean) interfaces and for those with a thin oxide layer separating the metal and semiconductor. These results are considered in terms of existing theories. The adhesion of contacts is considered and the influence of annealing on contact behaviour briefly discussed. Au and Ag readily diffuse into InP but Al contacts are thermally more stable.