Compositional dependence of Schottky barrier heights for Au on chemically etched InxGa1−xP surfaces

Abstract

Measurements of the Au Schottky barrier height were carried out on thin films of n-InxGa1−xP, of various compositions epitaxially grown on n-GaAs substrates. Conventional C–V, I–V, and photo response techniques were used. The junction was formed by evaporating Au in an ion-pumped vacuum system onto a InxGa1−xP surface which had been chemically etched (5H2SO4:1H2O2:1H2O at 40 °C for 90 s). Barrier heights determined from the I–V and photoresponse were found to be in good agreement while the C–V measurement encountered difficulties. The Au barrier, φp, to p-InxGa1−xP was found to be independent of composition. The barrier, φp, was determined by the relation φp+φn=φg where φg is the bandgap energy and φn is the measured barrier to n-InxGa1−xP. It has been observed that the Au barrier height to p-type material for most compound semiconductors is determined by the anion, thus p-InP and p-GaP have the same Au barrier, about 0.76 eV. This dependence on the anion of the compound has now been seen to extend to the alloy system InxGa1−xP measured here. While chemically etched specimens yielded diodes with reproducible barrier heights, diodes formed on surfaces which were untreated or cleaned only with organic solvents were of poor quality with varying barrier heights or even ohmic contacts.