Semiconductor devices and methods of manufacture

A semiconductor device includes a substrate comprising a material selected from the group consisting of AlN, SiC, GaN, sapphire and combinations thereof. An n+ type epitaxial layer is disposed above substrate and comprises GaN or AlGaN. An n- type epitaxial layer is disposed above substrate and comprises GaN or AlGaN. A p+-n junction grid comprising p+ GaN or p+ AlGaN is formed on selective areas of the n- type epitaxial layer. A metal layer is disposed over the p+-n junction grid and forms a Schottky contact. Another metal layer is deposited on one of the substrate and the n+ type epitaxial layer and forms a cathode electrode. A method of fabricating a semiconductor device is provided and includes forming a p+-n junction grid on a drift layer comprising GaN or AlGaN.