Se-passivated Si(100) surface for low and negative Schottky barriers

The Schottky barrier height at a metal/Si interface is ideally determined by the difference between metal work function and Si electron affinity for n-type Si. In reality, interface states between metal and Si pin the interface Fermi level, making the barrier height more or less independent of the ideal barrier height. We demonstrate that, by terminating dangling bonds on n-type Si(100) with a monolayer of Se, interface states are significantly reduced between metal and Si. As a result, low Schottky barriers are obtained for metals with low ideal barrier heights, such as Al and Cr. A negative Schottky barrier is demonstrated between Si and Ti, a metal commonly-used in the semiconductor industry. The negative Schottky barrier is thermally stable up to 400°C. For metals with high ideal barrier heights, inconsistency is observed between ideal barrier height and measured barrier height even with Se passivation.