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 Phi (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 Phi (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 Phi (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.