Reverse breakdown voltages larger than 1 kV have been reported for both unterminated Ga2O3 vertical rectifiers (1000- 1600 V) and field-plated Schottky diodes (1076-2300 V) with an epi thickness of 8-20 μm. If the doping is in the 1016 cm-3 range, the breakdown is usually in the 500-800V regime. Furthermore, the switching characteristics of discrete Ga2O3 vertical Schottky rectifiers exhibited reverse recovery times in the range of 20 to 30 ns. Large area (up to 0.2 cm2 ) Ga2O3 rectifiers were fabricated on a Si-doped n-Ga2O3 drift layer grown by halide vapor phase epitaxy on a Sn-doped n+ Ga2O3 (001) substrate. A forward current of 2.2 A was achieved in single-sweep voltage mode, a record for Ga2O3 rectifiers. The on-state resistance was 0.26 Ω·cm2 for these largest diodes, decreasing to 5.9 × 10-4 Ω·cm2 for 40x40 μm2 devices. We detail the design and fabrication of these devices. In addition, an inductive load test circuit was used to measure the switching performance of field-plated, edge-terminated Schottky rectifiers with a reverse breakdown voltage of 760 V (0.1 cm diameter, 7.85x10-3 cm2 area) and an absolute forward current of 1 A on 8 Μm thick epitaxial β-Ga2O3 drift layers. These devices were switched from 0.225 A to -700 V with trr of 82 ns, and from 1 A to -300 V with trr of 64 ns and no significant temperature dependence up to 125°C. There was no significant temperature dependence of trr up to 150°C.
Ga2O3 is gaining attention for high breakdown electronics. The β-polymorph is air-stable, has a wide bandgap (~4.6 eV) and is available in both bulk and epitaxial form. Different types of power diodes and transistors fabricated on Ga2O3 have shown impressive performance. Etching processes for Ga2O3 are needed for patterning for mesa isolation, threshold adjustment in transistors, thinning of nano-belts and selective area contact formation. Electrical damage in the near-surface region was found through barrier height changes of Schottky diodes on the etched surface. The damage is created by energetic ion bombardment, but may also consist of changes to near-surface stoichiometry through loss of lattice elements or deposition of etch residues. Annealing at 450°C removes this damage. We also discuss recent results on damage introduction by proton and electron irradiation. In this case, the carrier removal rates are found to be similar to those reported for GaN under similar conditions of dose and energy of the radiation.
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