Lateral Rutile GeO2 MOSFET Devices on Single-Crystal r-GeO2 Substrates
K. Tetzner1, Z. Galazka2, A. Thies1, A. Külberg1, and O. Hilt1
Published in:
IEEE Electron Device Lett., vol. 47, no. 3, pp. 566-569, doi:10.1109/LED.2025.3638262 (2026).
Abstract:
We report on the fabrication and electrical characterization of rutile GeO2 (r-GeO2) MOSFETs on single-crystal insulating (110) substrates prepared from crystals grown by the top-seeded solution growth. P+ ion implantation was used to define both the channel and ohmic contact regions. Transfer-length method measurements revealed nearly ideal ohmic characteristics for highly doped channels, allowing extraction of contact and sheet resistances of 12.4 Ω·mm and 2835 Ω/sq, respectively. Transistor devices exhibited drain currents up to 100 mA/mm demonstrating high current capability of r-GeO2 but showed no gate control due to the high channel carrier density. In contrast, lower-doped devices showed excellent current modulation with on/off ratios > 108, though with reduced on-state currents of 350 —A/mm, consistent with lower dopant activation. Furthermore, a threshold voltage of −6.8 V, an on-resistance (Ron) of 24 kΩ, and a subthresh- old swing of ∼400 mV/dec were achieved. Three-terminal off-state breakdown measurements of devices featuring low-doped channels yielded catastrophic breakdown at ∼1.3 kV, corresponding to an average drift-zone break- down field of 1.3 MV/cm. Combined with a specific Ron of 3.6 Ω cm2, a Baliga’s Figure of Merit of 0.5 MW/cm2 is obtained. These results represent the first demonstration of functional r-GeO2 MOSFETs on single-crystal insulating substrates and highlight the strong potential of this emerg- ing ultrawide-bandgap semiconductor for next-generation high-voltage power electronics.
1 Ferdinand-Braun-Institut (FBH), 12489 Berlin, Germany
2 Leibniz-Institut für Kristallzüchtung (IKZ), 12489 Berlin, Germany
Index Terms:
GeO2, MOSFET, implantation, power device, ohmic contacts, breakdown.
© 2025 The Authors. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
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