LAUSR

Optimized vertical heterojunction rectifiers with a diameter of 100 µm, consisting of sputter-deposited p-type NiO forming a p–n junction with thick (10 µm) Ga2O3 drift layers grown by halide vapor phase epitaxy (HVPE) on (001) Sn-doped (1019 cm−3) β-Ga2O3 substrates, exhibited breakdown voltages >8 kV over large areas (>1 cm2). The key requirements were low drift layer doping concentrations (<1016 cm3), low power during the NiO deposition to avoid interfacial damage at the heterointerface and formation of a guard ring using extension of the NiO beyond the cathode metal contact. Breakdown still occurred at the contact periphery, suggesting that further optimization of the edge termination could produce even larger breakdown voltages. On-state resistances without substrate thinning were <10 mΩ.cm−2, leading to power figure-of-merits >9 GW.cm−2. The devices showed an almost temperature-independent breakdown to 600 K. These results show the remarkable potential of NiO/Ga2O3 rectifiers for performance beyond the limits of both SiC and GaN. The important points to achieve the excellent performance were: (1) low drift doping concentration, (2) low power during the NiO deposition and (3) formation of a guard ring.