Thermal stability of ohmic contacts between Ti and Se-passivated n-type Si(001)

Abstract

The thermal stability of the interface between Ti and Se-passivated n-type Si(001) is investigated. As-deposited Ti contacts show ohmic characteristics. After annealing at temperatures from 200 °C to 480 °C in air, the Se-passivated samples are much more resistant to Schottky transition as compared to the bare samples. The bare samples turn to Schottky below 300 °C, whereas the passivated samples are ohmic all the way to 400 °C. A difference of over 100 °C is observed between the two types of samples. Schottky barrier heights are determined using capacitance–voltage and activation–energy methods. The bare samples reach a maximum barrier height of 0.39 eV as determined by activation–energy measurements, while the passivated samples maximize at 0.19 eV. We deduce that a monolayer of Se suppresses silicidation between Ti and Si by eliminating dangling bonds on Si(001).