The invention discloses an epitaxial wafer for a diode and a fabrication method of the epitaxial wafer. The epitaxial wafer for the diode comprises a substrate and a GaN two-dimensional growth layer, an SiNx template layer, a GaN recovery layer, a heavily-doped nGaN layer and a light-doped nGaN layer which sequentially cover the substrate along a thickness direction of the substrate, the epitaxial wafer also comprises an AlGaN cap layer, wherein the AlGaN cap layer covers the other side surface, departing from one side of the heavily-doped nGaN layer, of the light-doped nGaN layer, the substrate is a sapphire plain film substrate with an AlN cover layer, the SiNx template layer is formed by in-situ growth of SiH4 and NH3 on the other side surface, departing from one side of the substrate, of the GaN two-dimensional growth layer, and the thickness of the SiNx layer is lower than the thickness of an atomic layer. A diode electronic device fabricated from the epitaxial wafer disclosed by the invention is relatively low in electric leakage and long in service lifetime, the barrier height of a surface layer is increased, the reverse breakdown voltage is remarkably increased, and meanwhile, the positive conduction voltage cannot be risen.