Schottky Barrier Lowering Induced by Ultrathin Aluminum Oxynitride Interlayer in Metal/SiC Junctions

Abstract

It is known that the electrical characteristics of SiC Schottky diode depend strongly on the interface energy barrier (Schottky barrier) and lower Schottky barriers bring essential advantages of improving the power efficiency and obtaining the fast switching. In this work, the Schottky barrier of metal/SiC junction is reported experimentally to be reduced significantly with an ultra-thin (down to ~1.0 nm) aluminum oxynitride (AlON) interlayer inserted at the junction interface. It was also found that the contact resistance of junction decreased with the AlON interlayer. The barrier height was lowered by up to 0.8 eV and the reduction was similar for three types of metal with different work function (Pt: 5.65 eV, Ni: 5.01 eV, Cu: 4.33 eV). The adjustment of Schottky barrier with an interlayer is generally considered due to the potential change driven by fixed changes in the interlayer or Fermi-level depinning associated with the suppression of metal-induced gap states. In our case, the Fermi-level pinning factor remained almost unchanged (Fig. 1), implying that the surface states of SiC is NOT the main factor of the observed Schottky barrier reduction. It seems most likely that the Schottky barrier reduction arises from the fixed positive charges in the AlON thin film.