Metal/intrinsic diamond/semiconducting diamond junction diodes fabricated from polycrystalline diamond films

The electrical properties of metal/intrinsic semiconductor/semiconductor junctions formed by Al, undoped polycrystalline diamond, and B-doped p-type polycrystalline diamond films were investigated. These results are compared with those of standard metal/semiconductor junctions formed by direct metallization of Al on p-type semiconducting diamond. Polycrystalline diamond samples were grown using a microwave plasma-assisted chemical vapor deposition technique. These diamond thin films were then annealed, and chemically cleaned in order to stabilize their electrical properties prior to metallization. Good rectifying characteristics, with rectification ratios of 106–107 at 5 V, were obtained for metal-intrinsic diamond-semiconducting diamond junctions. Reverse bias breakdown voltages in excess of 20 V were observed with increasing thickness of the undoped diamond layer. Rectification was observed at 300 °C with a ratio of forward to reverse current of 103 at 5 V. A first-order model has been proposed to explain the effects of the undoped layer on the electrical characteristics of this junction diode. Only poor rectifying characteristics were obtained for metal-semiconductor junctions.