Progress of Investigation on the Schottky Barrier and Ohmic Contacts at Metal/III Nitride Interface

The Schottky barrier and ohmic contacts at metal/Ⅲ-nitride interfaces are the key technology to develop the blue and ultraviolet optical devices and high temperature, high power electronic devices. Ⅲ-nitrides are polar semiconductor with low density of surface states, so that the Fermi level pinning is rather weak and the surface treatments have obvious influence on contact characteristics. The surface contamination and oxidation also deteriorate the contact property. In addition, the high ionization energy of impurity in wide bandgap semiconductors makes difficulties in the raising of density of ionized impurities, and many deep traps may also capture the carriers. All these items increase the degree of difficulty in producing the high-quality contacts, so that it is necessary to find new schemes to improve the contact properties. The physical models to improve these contact properties are summarized in this paper in the hope of providing some new ideas for researchers engaged in devices.