A comparative study of electrochemically formed and vacuum-deposited n-GaAs/Au Schottky barriers using ballistic electron emission microscopy (BEEM)

A comparative study between n-GaAs/Au contacts, formed by electrochemical deposition or by vacuum evaporation, is presented. The main parameter, the barrier height Φ B , was determined using three methods, i.e. classical current-voltage and capacitance-voltage measurements as well as STM-based ballistic electron emission microscopy (BEEM). The latter method allowed us to determine the distribution of Φ B over the contact area on a nanometre scale and showed that the electrochemically made contacts are inhomogeneous. The main result, confirmed by the three methods, was that Φ B was higher for the electrochemically deposited contacts than for the evaporated ones. This higher value is attributed to O - groups, present at the interface during the electrochemical metallization, and forming interfacial dipoles with the Au, leading to an increase of the barrier.