Normally-OFF Two-Dimensional Hole Gas Diamond MOSFETs Through Nitrogen-Ion Implantation

Nobutaka Oi, Takuya Kudo, Masafumi Inaba, Satoshi Okubo, Shinobu Onoda, Atsushi Hiraiwa, Hiroshi Kawarada*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Diamond is a promising material for power applications owing to its excellent physical properties. Two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with hydrogen-terminated (C-H) channel have high current densities and high breakdown fields but often show normally- ON operation. From the viewpoint of safety, normally- OFF operation is required for power applications. In this letter, we used ion implantation to form a shallow and thin nitrogen-doped layer below the C-H channel region, which realized normally- OFF operation. Nitrogen-ion implanted length is fixed at 5 or 10 \mu \text{m}. Nitrogen is a deep donor (1.7 eV) and the nitrogen-doped layer prevents hole accumulation near the surface. The threshold voltage was as high as -2.5 V and no obvious dependence on the threshold voltage of nitrogen-ion implanted length is observed. The breakdown field was 2.7 MV/cm at room temperature. Of 64 devices with a common gate length, 75% showed normally- OFF operation. We confirmed the threshold voltage shift by a thin and shallow nitrogen-doped layer formed by ion implantation.

Original languageEnglish
Article number8715486
Pages (from-to)933-936
Number of pages4
JournalIEEE Electron Device Letters
Issue number6
Publication statusPublished - 2019 Jun


  • Diamond
  • high voltage
  • normally-off
  • wide bandgap semiconductor

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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