Insulator engineering in GaN-based MIS HFETs

Narihiko Maeda*, Masanobu Hiroki, Noriyuki Watanabe, Yasuhiro Oda, Haruki Yokoyama, Takuma Yagi, Toshiki Makimoto, Takatomo Enoki, Takashi Kobayashi

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Citations (Scopus)


Insulated-gate AlGaN/GaN heterostructure field-effect transistors (HFETs), i.e., GaN-based metal-insulator-semiconductor (MIS) HFETs, have been fabricated that exhibited excellent DC and RF characteristics together with the reduced gate leakage current (Ig). The Al2O3/ Si 3N4 bilayer gate insulator was used to simultaneously utilize (i) the high-quality interface between Si3N4 and AlGaN, and (ii) the high resistivity and high dielectric constant of Al 2O3. The Ig was less than 10-4 A/mm even at a gate voltage of +3 V. In a device with a gate length of 0.1 μm, the drain current was 1.30 A/mm, and the cut-off frequency (fT) and maximum oscillation frequency (fmax) were 70 and 90 GHz, respectively. Moreover, the deposition effect of insulators on the electrical properties in AlGaN/GaN heterostructures has been examined and theoretically analyzed for Si- and Al-based insulators (Si3N4, SiO 2, AlN, and Al2O3), because insulators are commonly used for surface passivation as well as the gate insulator, and hence, clarifying the insulator deposition effect is a fundamental issue in GaN-based HFETs. The increase in the two-dimensional electron gas (2DEG) was observed for all the insulators, and the effect was found to vary among insulators. One result is that Al2O3 was most effective to increase N s. The results were explained in terms of the change in the potential profile. The band engineering including insulators is proposed to be indispensable for interpreting and designing the device performance, because, through the potential profile change, the essential device parameters are altered such as the source resistance, the channel resistance under the insulated-gate, and its threshold voltage.

Original languageEnglish
Title of host publicationGallium Nitride Materials and Devices II
Publication statusPublished - 2007
Externally publishedYes
EventGallium Nitride Materials and Devices II - San Jose, CA, United States
Duration: 2007 Jan 222007 Jan 25

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceGallium Nitride Materials and Devices II
Country/TerritoryUnited States
CitySan Jose, CA


  • AlGaN/GaN HFET
  • AlO /SiN
  • GaN-based HFET
  • Insulated-gate
  • Insulator engineering
  • Surface passivation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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