- Physical Review Journals
All JournalsPhysics Magazine
Access Provided by Xinjiang University

Physical Review Materials

Export citation

Export citation

Choose format for download:

Download Citation
  • Access by Xinjiang University

Electrical stability of Cr2O3/β-Ga2O3 and NiOx/β-Ga2O3 heterojunction diodes

Yizheng Liu*, Haochen Wang, Carl Peterson, Chinmoy Nath Saha, Chris G. Van de Walle, and Sriram Krishnamoorthy†

  • *Contact author: yizhengliu@ucsb.edu
  • †Contact author: sriramkrishnamoorthy@ucsb.edu
PDF

Phys. Rev. Materials 10, 064605 – Published 22 June, 2026

DOI: https://doi.org/10.1103/wscr-3vxz

Abstract

This work reports the electrical characteristics comparison study between Cr2O3 and NiOx based heterojunction diodes (HJD) on halide vapor phase epitaxy (HVPE) grown β-Ga2O3 epitaxial layers. Both as-fabricated Cr2O3 and NiOx HJDs exhibited forward current density in a range of 130–150 A/cm2 at 5 V with rectifying ratios >1010 and a reverse leakage current density at 10−8 A/cm2 at −5V. The differential specific on-resistance of Cr2O3 and NiOx HJDs was 12.01mΩcm2 and 12.05mΩcm2, respectively. Breakdown voltages of Cr2O3 HJDs ranged from 1.4–1.9 kV and 1.5–2.3 kV for NiOx HJDs. Theoretical band alignment between Cr2O3 and β-Ga2O3 was calculated from first principles. The ambient exposed NiOx/HVPE β-Ga2O3 HJDs’ forward current density degraded after 10 days while that of Cr2O3/HVPE β-Ga2O3 HJDs’ remained nearly unchanged after the same amount of time. It was later confirmed that the ambient exposed sputtered NiOx sheet resistance (Rsh) degradation gave rise to the reduction of the forward current density of the NiOx based HJDs, and water (H2O) was qualitatively determined to be the agent attributed to the forward conduction degradation by measuring the Rsh of NiOx-on-sapphire reference wafer after exposing it to different environments. The Cr2O3/HVPE β-Ga2O3 HJD also exhibited enhanced thermal stability compared to the NiOx/β-Ga2O3 heterostructures at elevated temperatures.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (48)

  1. A. T. Neal, S. Mou, S. Rafique, H. Zhao, E. Ahmadi, J. S. Speck, K. T. Stevens, J. D. Blevins, D. B. Thomson, and N. Moser, Donors and deep acceptors in β-Ga2O3, Appl. Phys. Lett. 113, 062101 (2018).
  2. A. Bhattacharyya, C. Peterson, K. Chanchaiworawit, S. Roy, Y. Liu, S. Rebollo, and S. Krishnamoorthy, Over 6 µm thick MOCVD-grown low-background carrier density (1015cm−3) high-mobility (010) β-Ga2O3 drift layers, Appl. Phys. Lett. 124, 010601 (2024).
  3. C. Peterson, A. Bhattacharyya, K. Chanchaiworawit, R. Kahler, S. Roy, Y. Liu, S. Rebollo, A. Kallistova, T. E. Mates, and S. Krishnamoorthy, 200cm2/Vs electron mobility and controlled low 1015cm−3 Si doping in (010) β-Ga2O3 epitaxial drift layers, Appl. Phys. Lett. 125, 182103 (2024).
  4. S. Rebollo, Y. Liu, C. Peterson, S. Krishnamoorthy, and J. S. Speck, Growth of nitrogen-doped (010) β-Ga2O3 by plasma-assisted molecular beam epitaxy using an O2/N2 gas mixture, Appl. Phys. Lett. 126, 082106 (2025).
  5. C. Peterson, C. N. Saha, R. Kahler, Y. Liu, A. Mattapalli, S. Roy, and S. Krishnamoorthy, Kilovolt-class β-Ga2O3 field-plated Schottky barrier diodes with MOCVD-grown intentionally 1015cm−3 doped drift layers, J. Appl. Phys. 138, 082106 (2025).
  6. S. Roy, B. Kostroun, Y. Liu, J. Cooke, A. Bhattacharyya, C. Peterson, B. Sensale-Rodriguez, and S. Krishnamoorthy, Low QCVF 20A/1.4 kV β-Ga2O3 vertical trench high-k RESURF schottky barrier diode with turn-on voltage of 0.5 V, IEEE Electron Device Lett. 45, 2487 (2024).
  7. S. Roy, B. Kostroun, J. Cooke, Y. Liu, A. Bhattacharyya, C. Peterson, B. Sensale-Rodriguez, and S. Krishnamoorthy, Ultra-low reverse leakage in large area kilo-volt class β-Ga2O3 trench Schottky barrier diode with high-k dielectric RESURF, Appl. Phys. Lett. 123, 243502 (2023).
  8. C. N. Saha, S. Roy, Y. Liu, C. Peterson, and S. Krishnamoorthy, 2.34 kV β-Ga2O3 vertical trench RESURF Schottky barrier diode with sub-micron fin width, APL Electronic Devices 1, 046125 (2025).
  9. Y. Zhang and J. S. Speck, Importance of shallow hydrogenic dopants and material purity of ultra-wide bandgap semiconductors for vertical power electron devices, Semicond. Sci. Technol. 35, 125018 (2020).
  10. B. J. Baliga, Fundamentals of Power Semiconductor Devices (Springer Science & Business Media, New York, 2010).
  11. J. Wan, H. Wang, C. Zhang, Y. Li, C. Wang, H. Cheng, J. Li, N. Ren, Q. Guo, and K. Sheng, 3.3 kV-class NiO/β-Ga2O3 heterojunction diode and its off-state leakage mechanism, Appl. Phys. Lett. 124, 243504 (2024).
  12. H. H. Gong, X. H. Chen, Y. Xu, F.-F. Ren, S. L. Gu, and J. D. Ye, A 1.86-kV double-layered NiO/β-Ga2O3 vertical p–n heterojunction diode, Appl. Phys. Lett. 117, 022104 (2020).
  13. J.-S. Li, C.-C. Chiang, X. Xia, H.-H. Wan, F. Ren, and S. J. Pearton, 7.5 kV, 6.2GWcm−2 NiO/β-Ga2O3 vertical rectifiers with on–off ratio greater than 1013, J. Vac. Sci. Technol. A 41, 030401 (2023).
  14. J.-S. Li, H.-H. Wan, C.-C. Chiang, T. J. Yoo, F. Ren, H. Kim, and S. J. Pearton, NiO/Ga2O3 vertical rectifiers of 7 kV and 1mm2 with 5.5 a forward conduction current, Cryst. 13, 1624 (2023).
  15. M. Xiao, B. Wang, J. Spencer, Y. Qin, M. Porter, Y. Ma, Y. Wang, K. Sasaki, M. Tadjer, and Y. Zhang, NiO junction termination extension for high-voltage (>3 kV) Ga2O3 devices, Appl. Phys. Lett. 122, 183501 (2023).
  16. F. Zhou et al., An avalanche-and-surge robust ultrawide-bandgap heterojunction for power electronics, Nat. Commun. 14, 4459 (2023).
  17. J.-S. Li, H.-H. Wan, C.-C. Chiang, T. J. Yoo, M.-H. Yu, F. Ren, H. Kim, Y.-T. Liao, and S. J. Pearton, Breakdown up to 13.5 kV in NiO/β-Ga2O3 vertical heterojunction rectifiers, ECS J. Solid State Sci. Technol. 13, 035003 (2024).
  18. Y. Qin, Z. Yang, H. Gong, A. G. Jacobs, J. Spencer, M. Porter, B. Wang, K. Sasaki, C.-H. Lin, and M. Tadjer, 10 kV, 250 °C operational, enhancement-mode Ga2O3 JFET with charge-balance and hybrid-drain designs, in 2024 IEEE International Electron Devices Meeting (IEDM) (IEEE, New York, 2024), pp. 1–4.
  19. Y. Qin, M. Xiao, M. Porter, Y. Ma, J. Spencer, Z. Du, A. G. Jacobs, K. Sasaki, H. Wang, and M. Tadjer, 10-kV Ga2O3 charge-balance Schottky rectifier operational at 200 °C, IEEE Electron Device Lett. 44, 1268 (2023).
  20. Y. Liu, S. M. Witsell, J. F. Conley, and S. Krishnamoorthy, Orientation-dependent β-Ga2O3 heterojunction diode with atomic layer deposition (ALD) NiO, Appl. Phys. Lett. 127, 122109 (2025).
  21. Y. Qin, M. Xiao, R. Zhang, Q. Xie, T. Palacios, B. Wang, Y. Ma, I. Kravchenko, D. P. Briggs, and D. K. Hensley, 1 kV GaN-on-Si quasi-vertical Schottky rectifier, IEEE Electron Device Lett. 44, 1052 (2023).
  22. Y. Ma et al., Wide-bandgap nickel oxide with tunable acceptor concentration for multidimensional power devices, Adv Elect Materials 11, 2300662 (2025).
  23. Y. Qin, M. Porter, M. Xiao, Z. Du, H. Zhang, Y. Ma, J. Spencer, B. Wang, Q. Song, and K. Sasaki, 2 kV, 0.7mΩcm2 vertical Ga2O3 superjunction schottky rectifier with dynamic robustness, in 2023 International Electron Devices Meeting (IEDM) (IEEE, New York, 2023), pp. 1–4.
  24. M. Xiao, Y. Ma, Z. Du, Y. Qin, K. Liu, K. Cheng, F. Udrea, A. Xie, E. Beam, and B. Wang, First demonstration of vertical superjunction diode in GaN, in 2022 International Electron Devices Meeting (IEDM) (IEEE, New York, 2022), pp. 35–36.
  25. K. Egbo, E. M. Garrity, W. A. Callahan, C. Chae, C.-W. Lee, B. Tellekamp, J. Hwang, V. Stevanovic, and A. Zakutayev, NiGa2O4 interfacial layers in NiO/Ga2O3 heterojunction diodes at high temperature, Appl. Phys. Lett. 124, 173512 (2024).
  26. D. S. Yu, L. Meng, V. G. T. Vangipuram, C. Chae, J. Hwang, and H. Zhao, Metal–organic chemical vapor deposition of p-type NiO and NiO/β-Ga2O3 PN diodes, APL Electronic Devices 1, 046104 (2025).
  27. M. T. Greiner, M. G. Helander, W.-M. Tang, Z.-B. Wang, J. Qiu, and Z.-H. Lu, Universal energy-level alignment of molecules on metal oxides, Nat. Mater. 11, 76 (2012).
  28. S. Ghosh, M. Baral, R. Kamparath, R. J. Choudhary, D. M. Phase, S. D. Singh, and T. Ganguli, Epitaxial growth and interface band alignment studies of all oxide α-Cr2O3/β-Ga2O3 pn heterojunction, Appl. Phys. Lett. 115, 061602 (2019).
  29. H. Mashiko, T. Oshima, and A. Ohtomo, Band-gap narrowing in α−(CrxFe1−x)2O3 solid-solution films, Appl. Phys. Lett. 99, 241904 (2011).
  30. C. Su, H. Zhou, Z. Hu, C. Wang, Y. Hao, and J. Zhang, 1.96 kV p-Cr2O3/β-Ga2O3 heterojunction diodes with an ideality factor of 1.07, Appl. Phys. Lett. 126, 132104 (2025).
  31. Y. Feng, et al., 120 A/1.78 kV p-Cr2O3/n-β-Ga2O3 heterojunction PN diodes with slanted mesa edge termination, IEEE Electron Device Lett. 46, 1705 (2025).
  32. W. A. Callahan, K. Egbo, C.-W. Lee, D. Ginley, R. O’Hayre, and A. Zakutayev, Reliable operation of Cr2O3:Mg/β-Ga2O3 p–n heterojunction diodes at 600 °C, Appl. Phys. Lett. 124, 153504 (2024).
  33. Y. Liu, S. Roy, C. Peterson, A. Bhattacharyya, and S. Krishnamoorthy, Ultra-low reverse leakage NiOx/β-Ga2O3 heterojunction diode achieving breakdown voltage >3kV with plasma etch field-termination, AIP Adv. 15, 015114 (2025).
  34. C. G. Van de Walle and J. Neugebauer, Universal alignment of hydrogen levels in semiconductors, insulators and solutions, Nature 423, 626 (2003).
  35. W. Kohn and L. J. Sham, Self-consistent equations including exchange and correlation effects, Phys. Rev. 140, A1133 (1965).
  36. J. Heyd, G. E. Scuseria, and M. Ernzerhof, Erratum: Hybrid functionals based on a screened Coulomb potential, J. Chem. Phys. 118, 8207 (2003); 124, 219906 (2006).
  37. P. E. Blöchl, Projector augmented-wave method, Phys. Rev. B 50, 17953 (1994).
  38. G. Kresse and D. Joubert, From ultrasoft pseudopotentials to the projector augmented-wave method, Phys. Rev. B 59, 1758 (1999).
  39. G. Kresse and J. Furthmüller, Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set, Phys. Rev. B 54, 11169 (1996).
  40. C. Freysoldt, B. Grabowski, T. Hickel, J. Neugebauer, G. Kresse, A. Janotti, and G. C. Van de Walle, First-principles calculations for point defects in solids, Rev. Mod. Phys. 86, 253 (2014).
  41. C. Freysoldt, J. Neugebauer, and C. G. Van de Walle, Fully Ab initio finite-size corrections for charged-defect supercell calculations, Phys. Rev. Lett. 102, 016402 (2009).
  42. C. Freysoldt, J. Neugebauer, and C. G. Van de Walle, Electrostatic interactions between charged defects in supercells, Phys. Status Solidi 248, 1067 (2011).
  43. J. B. Varley, J. R. Weber, A. Janotti, and C. G. Van de Walle, Oxygen vacancies and donor impurities in β-Ga2O3, Appl. Phys. Lett. 97, 142106 (2010).
  44. A. Fiedler, R. Schewski, Z. Galazka, and K. Irmscher, Static dielectric constant of β-Ga2O3 perpendicular to the principal planes (100),(010), and (001), ECS J.Solid State Sci. Technol. 8, Q3083 (2019).
  45. S. Roy, A. Bhattacharyya, C. Peterson, and S. Krishnamoorthy, 2.1 kV (001)-β-Ga2O3 vertical Schottky barrier diode with high-k oxide field plate, Appl. Phys. Lett. 122, 152101 (2023).
  46. J. Pan, C. Li, H. Geng, Y. Ni, C. Wu, H. Wu, S. Wang, F. Wu, and D. Guo, Band engineering to suppress dark current in self-powered solar-blind photodetectors for optoelectronics in harsh environments, Phys. Rev. Appl. 24, 064043 (2025).
  47. S. Jin, Y. Weng, H. Xu, M. A. Iqbal, K. Chen, A. Chen, and D. Guo, Solar-blind deep ultraviolet photoelectrochemical detectors: Materials, mechanisms, and applications, Mater. Today Phys. 59, 101869 (2025).
  48. C. Buttay, C. Raynaud, H. Morel, G. Civrac, M.-L. Locatelli, and F. Morel, Thermal stability of silicon carbide power diodes, IEEE Trans. Electron Devices 59, 761 (2012).

Outline

Information

Phys. Rev. Materials 10, 064605– Published 22 June, 2026
  • Received 13 December 2025
  • Accepted 12 May 2026
Article part of CHORUS
Crossmark - Check for updates button

©2026 American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation