3.3 kV-class NiO/β-Ga2O3 heterojunction diode and its off-state leakage mechanism

This Letter demonstrates a high-performance 3.3 kV-class β-Ga2O3 vertical heterojunction diode (HJD) along with an investigation into its off-state leakage mechanism. The vertical β-Ga2O3 HJD with field plate assisted deep mesa (FPDM) termination was fabricated using a self-aligned technique to etch the deep mesa to a depth of 9 μm, thereby reducing electric field crowding at the anode edge. In addition, a thick dielectric is deposited to fill the trench, facilitating the utilization of a field plate to further reduce the electric field at the anode edge. TCAD (Technology Computer Aided Design) simulations show significant suppression of electric field crowding at the anode edge. The fabricated HJD exhibits a high current swing of ∼1010 over a temperature range from 25 °C to 175 °C. The specific on-resistance (Ron,sp) is extracted to be 3.9 mΩ cm2, and the breakdown voltage is 3.42 kV with the FPDM termination. These conduction and blocking characteristics lead to a high power figure of merit of 3 GW/cm2, which is one of the highest among multi-kilovolt β-Ga2O3 diodes. Furthermore, the off-state current leakage mechanism of the HJD under a reverse bias up to 2000 V was investigated. The fitted results reveal that the leakage current is primarily dominated by Poole–Frenkel (PF) emission, with the trap level of PF extracted to be 0.36 eV below the conduction band of NiO.