Reproducible NiO/Ga2O3 Vertical Rectifiers with Breakdown Voltage >8 kV

Abstract

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.

1 mm2, 3.6 kV, 4.8 A NiO/Ga2O3 Heterojunction Rectifiers

“…We have recently examined the high temperature performance of NiO/Ga 2 O 3 rectifiers and found them to be much more stable up to 600 K than Schottky rectifiers fabricated on the same wafers. 47,48 Such devices exhibit breakdown fields >8.5 MV.cm −1 , establishing this as a lower limit for β-Ga 2 O 3 . 49…”

Operation of NiO/β-(Al0.21Ga0.79)2O3/Ga2O3 Heterojunction Lateral Rectifiers at up to 225 °C

“…Recent progress in extending the breakdown voltage above 8 kV in vertical rectifiers has shown the value of field management. [55][56][57] Acknowledgments Work performed as part of Interaction of Ionizing Radiation with Matter University Research Alliance (IIRM-URA),…”

15 MeV proton damage in NiO/β-Ga2O3vertical rectifiers

“…The vertical rectifiers have been described in detail previously [23][24][25], but in brief consist of 10 µm drift region of lightly n-type Ga 2 O 3 grown on a conducting n + Ga 2 O 3 . NiO with a total thickness of 20 nm is deposited on the top surface by sputtering and contacts made to both sides by e-beam evaporation of Ti/Au to the rear surface and Ni/Au to the NiO.…”

“…This has led to recent demonstrations of vertical rectifiers with breakdown voltages more than 8 kV with excellent high temperature operation [9]. While the device performance is promising in terms of dc and switching applications [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], little is known about the effects of radiation on these heterojunctions. While the Ga 2 O 3 is known to be relatively resistant to total dose damage [27,28], large reversible changes in current-voltage characteristics of the heterojunctions have been observed after Co-60 gamma ray exposure which appears to be due to conductivity changes in the NiO [29].…”