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 ${\mathrm{O}}_2$ ambient. The formation of rare earth metal oxides $({\mathrm{IrO}}_2$ and ${\mathrm{RuO}}_2)$ after ${\mathrm{O}}_2$ annealing led to the increase of Schottky barrier height (>1.9 eV) and a low reverse leakage current ${\text{(∼10}}^{\text{−9}}\hspace{0.17em}{\mathrm{A/cm}}^2\mathrm{).}$ Synchrotron radiation photoemission spectroscopy showed that the work function of ${\mathrm{IrO}}_2$ is higher about 0.23 eV than that of Ir and the binding energies of Si $\text{2p}$ and C $\text{1s}$ shifted toward lower binding energies by 0.12 eV in both ${\mathrm{O}}_2$ and ${\mathrm{N}}_2$ annealed samples. The oxidation annealing caused predominant Si outdiffusion to the ${\mathrm{IrO}}_2$ $({\mathrm{RuO}}_2\mathrm{),}$ 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.