Characteristics of Schottky contacts on n-type 4H–SiC using IrO2 and RuO2

Abstract

Thermally stable Schottky contacts on n-type 4H–SiC with high Schottky barrier height were demonstrated by annealing the rare earth metal contacts (Ir and Ru) under O2 ambient. The formation of rare earth metal oxides (IrO2 and RuO2) after O2 annealing led to the increase of Schottky barrier height (>1.9 eV) and a low reverse leakage current (∼10−9 A/cm2). Synchrotron radiation photoemission spectroscopy showed that the work function of IrO2 is higher about 0.23 eV than that of Ir and the binding energies of Si 2p and C 1s shifted toward lower binding energies by 0.12 eV in both O2 and N2 annealed samples. The oxidation annealing caused predominant Si outdiffusion to the IrO2 (RuO2), leaving Si vacancies behind, leading to the shift of surface Fermi level to the energy level of Si vacancy. Both the formation of oxide and the Fermi level movement played a role in forming the Schottky contact with high barrier height and excellent thermally stability.