The switching performance of unpackaged vertical geometry NiO/ β -Ga 2 O 3 rectifiers with a reverse breakdown voltage of 1.76 kV (0.1 cm diameter, 7.85 × 10 −3 cm 2 area) and an absolute forward current of 1.9 A fabricated on 20 μ m thick epitaxial β -Ga 2 O 3 drift layers and a double layer of NiO to optimize breakdown and contact resistance was measured with an inductive load test circuit. The Baliga figure-of-merit of the devices was 261 MW.cm −2 , with differential on-state resistance of 11.86 mΩ.cm 2 . The recovery characteristics for these rectifiers switching from forward current of 1 A to reverse off-state voltage of −550 V showed a measurement-parasitic-limited recovery time (t rr ) of 101 ns, with a peak current value of 1.4 A for switching from 640 V. The reverse recovery time was limited by extrinsic parasitic and thus does not represent the intrinsic device characteristics. There was no significant dependence of t rr on switching voltage or forward current.
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NiO/β-(Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 heterojunction lateral rectifiers with reverse breakdown voltage >7 kV
NiO/β-(Al x Ga 1− x ) 2 O 3 /Ga 2 O 3 heterojunction lateral geometry rectifiers with diameter 50–100 μm exhibited maximum reverse breakdown voltages >7 kV, showing the advantage of increasing the bandgap using the β-(Al x Ga 1− x ) 2 O 3 alloy. This Si-doped alloy layer was grown by metal organic chemical vapor deposition with an Al composition of ∼21%. On-state resistances were in the range of 50–2180 Ω cm 2 , leading to power figures-of-merit up to 0.72 MW cm −2 . The forward turn-on voltage was in the range of 2.3–2.5 V, with maximum on/off ratios >700 when switching from 5 V forward to reverse biases up to −100 V. Transmission line measurements showed the specific contact resistance was 0.12 Ω cm 2 . The breakdown voltage is among the highest reported for any lateral geometry Ga 2 O 3 -based rectifier.
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- Award ID(s):
- 1856662
- NSF-PAR ID:
- 10400690
- Date Published:
- Journal Name:
- Journal of Vacuum Science & Technology A
- Volume:
- 41
- Issue:
- 3
- ISSN:
- 0734-2101
- Page Range / eLocation ID:
- 032701
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Large area (1 mm2) vertical NiO/
β n-Ga2O/n+Ga2O3heterojunction rectifiers are demonstrated with simultaneous high breakdown voltage and large conducting currents. The devices showed breakdown voltages (VB) of 3.6 kV for a drift layer doping of 8 × 1015cm−3, with 4.8 A forward current. This performance is higher than the unipolar 1D limit for GaN, showing the promise ofβ -Ga2O3for future generations of high-power rectification devices. The breakdown voltage was a strong function of drift region carrier concentration, with VBdropping to 1.76 kV for epi layer doping of 2 × 1016cm−3. The power figure-of-merit, VB2/RON, was 8.64 GW·cm−2, where RONis the on-state resistance (1.5 mΩ cm2). The on-off ratio switching from 12 to 0 V was 2.8 × 1013, while it was 2 × 1012switching from 100 V. The turn-on voltage was 1.8 V. The reverse recovery time was 42 ns, with a reverse recovery current of 34 mA. -
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The characteristics of NiO/
β -(Al0.21Ga0.79)2O3/Ga2O3 heterojunction lateral geometry rectifiers with the epitaxial layers grown by metal organic chemical vapor deposition were measured over a temperature range from 25 °C–225 °C. The forward current increased with temperature, while the on-state resistance decreased from 360 Ω.cm2at 25 °C to 30 Ω.cm2at 225 °C. The forward turn-on voltage was reduced from 4 V at 25 °C to 1.9 V at 225 °C. The reverse breakdown voltage at room temperature was ∼4.2 kV, with a temperature coefficient of −16.5 V K−1. This negative temperature coefficient precludes avalanche being the breakdown mechanism and indicates that defects still dominate the reverse conduction characteristics. The corresponding power figures-of-merit were 0.27–0.49 MW.cm−2. The maximum on/off ratios improved with temperature from 2105 at 25 °C to 3 × 107 at 225 °C when switching from 5 V forward to 0 V. The high temperature performance of the NiO/β -(Al0.21Ga0.79)2O3/Ga2O3 lateral rectifiers is promising if the current rate of optimization continues. -
Vertical heterojunction NiO/β n-Ga 2 O/n + Ga 2 O 3 rectifiers employing NiO layer extension beyond the rectifying contact for edge termination exhibit breakdown voltages (V B ) up to 4.7 kV with a power figure-of-merits, V B 2 /R ON of 2 GW·cm −2 , where R ON is the on-state resistance (11.3 mΩ cm 2 ). Conventional rectifiers fabricated on the same wafers without NiO showed V B values of 840 V and a power figure-of-merit of 0.11 GW cm −2 . Optimization of the design of the two-layer NiO doping and thickness and also the extension beyond the rectifying contact by TCAD showed that the peak electric field at the edge of the rectifying contact could be significantly reduced. The leakage current density before breakdown was 144 mA/cm 2 , the forward current density was 0.8 kA/cm 2 at 12 V, and the turn-on voltage was in the range of 2.2–2.4 V compared to 0.8 V without NiO. Transmission electron microscopy showed sharp interfaces between NiO and epitaxial Ga 2 O 3 and a small amount of disorder from the sputtering process.more » « less
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Abstract A unique field termination structure combining a three-step field plate with nitrogen ion implantation to enhance the reverse breakdown performance of Pt/
β -Ga2O3Schottky barrier diodes (SBDs) and NiO/β -Ga2O3heterojunction diodes (HJDs) is reported. The fabricated devices showed a lowR on,spof 6.2 mΩ cm2for SBDs and 6.8 mΩ cm2for HJDs. HJDs showed a 0.8 V turn-on voltage along with an ideality factor of 1.1 leading to a low effective on-resistance of 18 mΩ cm2. The devices also showed low reverse leakage current (<1 mA cm−2) and a breakdown voltage of ∼1.4 kV. These results offer an alternative, simpler route for fabricating high-performance kilovolt-classβ -Ga2O3diodes.
