kV-class vertical p-n heterojunction rectifier based on ITO/diamond

Indium tin oxide (ITO) layers were sputter-deposited onto commercially available vertical p/p+ diamond structures consisting of 5 μm thick p-type (1.3 × 1016 cm−3) drift layers deposited by chemical vapor deposition on 250 μm thick heavily B-doped (3 × 1020 cm−3) single crystal substrates. The ITO is found to form a type II band alignment allowing Ohmic contact to the p-type diamond and creating a vertical n-p heterojunction. The maximum reverse breakdown of heterojunction rectifiers was ∼1.1 kV, with an on-resistance (RON) of 13 mΩ · cm2, leading to a power figure of merit of 99.3 MW/cm2. The on-voltage was 1.4 V, diode ideality factor was 1.22, with a reverse recovery time of 9.5 ns for 100 μm diameter rectifiers. The on/off ratios when switching from −5 V forward to 100 V reverse were in the range of 1011–1012. This is a simple approach for realizing high performance vertical diamond-based rectifiers for power switching applications.