Cr2O3/β-Ga2O3 heterojunction diodes on thick, mid-1015 cm−3 low-doped drift layer with 3.45 kV breakdown voltage

We demonstrate plasma-etch terminated Cr2O3/β-Ga2O3 heterojunction diodes (HJDs) on a low-doped (mid-1015 cm−3) 20 μm thick halide vapor phase epitaxy-grown drift layer. Bilayer Cr2O3 was deposited by reactive RF sputtering using a metallic Cr target and by tuning the Ar/O2 gas flow ratio. 1.5 μm self-aligned mesa etch was carried out using dry-etch based chemistry to achieve effective edge termination. Circular devices with 60–300 μm diameter exhibited breakdown voltages in the range of 3–3.4 kV with an ultralow reverse leakage (10−5–10−6 A/cm2) current density before breakdown. High-voltage capacitance-voltage measurement was carried out to extract the charge density profile up to 10–12 μm. The variation of (ND-NA) was within ±5% up to 12 μm, exhibiting uniform and controlled low doping [(4–5) × 1015 cm−3] across the thick drift layer. This is the lowest controlled doping demonstrated for a thick drift layer in β-Ga2O3. Room temperature I-V measurement shows 50 A/cm2 current density at 5 V forward voltage with Ron,sp = 60 mΩ cm2 after considering current spreading. A thick drift layer with uniform doping, optimization of the sputtering condition of Cr2O3, and deep mesa etch for edge termination are all crucial to achieve multi-kV class Cr2O3/β-Ga2O3 HJDs.