Relation between interface states and temperature behavior of the barrier height of silver contacts on clean cleaved n-type silicon

Abstract

The properties of silver-silicon interfaces formed by cleaving n-type silicon in ultra high vacuum (UHV) in a stream of evaporating silver atoms were studied. The barrier heights of these contacts were measured at different temperatures by using C- V techniques. All measurements were performed in UHV. The dependence of the barrier height upon temperature did not follow the temperature dependence of the Si band gap as it is usually found. The measured temperature behavior depended on the roughness of the Si surface. The temperature behavior can be explained by assuming a specific band structure of the interface states. For Ag contacts on atomically smooth n-type Si, the interface states were found to be arranged in two bands, one band 4 × 10 −3 eV wide with acceptor type states 0.18 eV below the intrinsic level E i and a density of 10 17 states/cm 2 eV, and the other 1 eV wide with donor type states with its upper edge 0.28 eV below E i, and a density of 4 × 10 14 states/cm 2eV.