NiO/Ga2O3 heterojunction rectifiers with >8.1 kV breakdown enabled by optimized field plate configuration

Vertical Ga2O3 heterojunction diodes were fabricated and systematically studied to evaluate the impact of lateral contact geometry on forward and reverse device performance. The devices were formed on 32 μm thick, lightly doped (8.6 × 1015 cm−3) β-Ga2O3 drift layers grown by halide vapor phase epitaxy on heavily doped n+ substrates. A NiO/Ni/Au heterojunction anode was employed together with dielectric edge termination using a 70 nm SiO2/30 nm SiN field-plate structure. Three device designs with different field plate dimensions (D = 10, 20, and 30 μm) between the first- and second-layer contact metals were investigated. Capacitance–voltage measurements indicate a free carrier concentration of approximately (8.6 ± 1.2) × 1015 cm−3 in the drift layer, while forward I–V characteristics showed comparable saturation currents and turn-on voltages for all designs. Increasing D resulted in a reduction in on-resistance and a significant suppression of reverse leakage current at low to moderate reverse bias. The optimized device with D = 30 μm exhibited the highest breakdown voltage of approximately 8.1 kV, compared with 5.5 and 4.5 kV for D = 20 μm and D = 10 μm, respectively. These results demonstrate that lateral contact spacing is a critical design parameter for electric-field management and breakdown enhancement in Ga2O3 heterojunction diodes.