Homoepitaxial diamond p–n+ junction with low specific on-resistance and ideal built-in potential

We have realized low specific on-resistance and ideal built-in potential simultaneously for a (111)-oriented homoepitaxial diamond p–n+ junction. As the p–n+ junction, the heavily phosphorus doped n+-type layer, which shows variable range hopping conduction, was formed on the (111)-oriented boron doped p-type one. By using this hopping conduction, the resistivity of the n+-type layer becomes lower by three orders of magnitude than that of a lightly P-doped layer. Current density–voltage characteristics showed a rectification ratio of 106 at ± 15 V at room temperature. The current density and the specific on-resistance at forward bias voltage of 15 V at room temperature are over 100 A/cm2 and 8 × 10− 2 Ωcm2, respectively. This low specific on-resistance corresponds to the lower resistivity of the n+-type layer by three orders of magnitude than that of conventional lightly P-doped n-type layer. The existence of the space-charge layer at the vicinity of the p–n+ junction was confirmed from capacitance–voltage (C–V) characteristics. From C−2–V characteristics at 200 °C, the built-in potential was estimated as approximately 4.4 eV, which is identical to that of conventional diamond p–n junction.