Lowering of the Schottky barrier height of metal/n-type 4H-SiC contacts using low-work-function metals with thin insulator insertion

We examined the lowering of the Schottky barrier height (SBH) of a metal/n-type 4H-silicon carbide (SiC) contact using low-work-function metals to realize an ohmic contact through a low-temperature process. We found that the SBHs of Y, Mg, and Hf/n-type 4H-SiC contacts deviated from the Schottky limit and that the SBH was greater than ∼0.5 eV at minimum. Inserting 0.3 and 0.7 nm thick SiN layers into a Mg/n-type 4H-SiC interface could help effectively reduce the SBH; Mg/SiN/n-type 4H-SiC exhibited an SBH as low as ∼0.36 eV. This reduction in the SBH could be attributed to the suppression of the metal-induced gap state manifested at the conduction band edge. Finally, through a quantitative analysis, it was demonstrated that the contact resistivity of a Mg/SiN (0.3 nm)/4H-SiC interface could be reduced by approximately one order of magnitude compared with that of a Mg/4H-SiC interface at donor concentrations below ∼3 × 10 cm