Area-dependent electrical characteristics of Schottky diodes fabricated on n-type GaN

The electrical characteristics of Schottky diodes fabricated on n-type GaN were investigated as a function of the contact area. A strong areal dependence was observed for all Schottky diodes, e.g., the larger the contact area, the smaller the Schottky barrier height, while the ideality factor retained a large value as high as 2.0 for all contact areas, likely due to the randomly-distributed threading dislocations observed via atomic force microscopy and/or to the plasma-induced surface states. A strong area-dependent Schottky barrier height could, therefore, be explained in terms of the barrier inhomogeneity model. In this transport regime, the Schottky characteristics exhibited an insignificant dependence on the work function of the Schottky metals; namely, Fermi level pinning occurred.