Hybrid Schottky and heterojunction vertical β-Ga2O3 rectifiers

Abstract

Junction barrier Schottky design Ga₂O₃ rectifiers allow for a combination of low turn-on voltage and high breakdown voltage. Ni/Au/Ga₂O₃ Schottky rectifiers and NiO/Ga₂O₃ heterojunction rectifiers were fabricated on the same wafer and the percentage of the relative areas and diameters of each were varied from pure Schottky devices to pure heterojunction devices. The on-voltage increased from 0.6 V for Schottky rectifiers to 2.4 V for heterojunction rectifiers, with a monotonic decrease in forward current at fixed bias of 5 V from 375 nA cm⁻² to 175 nA cm⁻². Conversely, the breakdown voltage increased monotonically as the proportion of heterojunction area increased, from 1.2 kV for Schottky rectifiers to 6.2 kV for pure heterojunction devices. Breakdown mostly was initiated at the edge of the anode contact but could also occur at the transition region from the Schottky contact to NiO edge termination. The Baliga figure of merit increased with both the relative percentage of area and diameter of the heterojunction contact from 0.2 GW cm⁻² to 3 GW cm⁻², while the energy loss during switching also increased from 2 to 3.9 W cm⁻². These trends illustrate the trade-offs of Schottky versus pn junctions for the operation of Ga₂O₃ rectifiers.