Influence of hydrogen treatment and annealing processes upon the Schottky barrier height of Au/n-GaAs and Ti/n-GaAs diodes

Abstract

After annealing in a H2 atmosphere at different temperatures, ⟨100⟩-oriented n-GaAs substrates were metallized with Au and Ti layers of different thicknesses to form Au/n-GaAs and Ti/n-GaAs Schottky diodes. The Schottky barrier height (SBH) variation and its dependence on subsequent N2 annealing for these Schottky diodes have been studied by different measurement techniques (I–V, C–V and BEEM) to obtain reliable values. These methods show that pre-metallization annealing leads to a less homogeneous metal semiconductor (MS) interface. In case of thick Au layers the effective barrier height is reduced as soon as the H2 annealing temperature reaches 300 °C. However, GaAs samples covered with thin Au layers or Ti layers do not exhibit such a barrier height reduction. The lower value in the case of thick Au layers is attributed to H+ groups, present at the interface due to the annealing in H2 atmosphere, forming interfacial dipoles with Au, leading to an inhomogeneous barrier and a decrease of the effective barrier height. It seems that these dipoles disappear again in the case of thin Au layers or are not formed with Ti. Post-metallization N2 annealing at higher temperatures lowers the barrier height for all samples. The resulting barrier inhomogeneities are explained and analysed using the bond polarization theory of Tung (2001 Phys. Rev. B 64 205310, 2001 Mater. Sci. Eng. R 35), a recent Schottky barrier formation model and the pinch-off model (Tung 1992 Phys. Rev. B 45 13509).