A Schottky diode includes a first nitride-based semiconductor layer disposed atop a substrate. A second nitride-based semiconductor layer is disposed atop a portion of the first nitride-based semiconductor layer. The second layer has a doping concentration lower than that of the first layer. A first Schottky contact metal layer having a first metal work function is disposed on a top planar surface of the second layer, forming a first Schottky junction. A second Schottky contact metal layer having a second metal work function is disposed atop of and laterally surrounding the first Schottky contact metal layer, the metal work function of the second metal layer is higher than that of the first metal layer. A metal layer disposed on first and second planar surfaces forms an ohmic contact with the first nitride-based semiconductor layer.