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

doi:10.1117/12.703659

8 February 2007 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

Author Affiliations +

Proceedings Volume 6473, Gallium Nitride Materials and Devices II; 647316 (2007) https://doi.org/10.1117/12.703659
Event: Integrated Optoelectronic Devices 2007, 2007, San Jose, California, United States

Abstract

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 (I_g). The Al₂O₃/ Si₃N₄ 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 Al₂O₃. 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 &mgr;m, the drain current was 1.30 A/mm, and the cut-off frequency (f_&Tgr;) and maximum oscillation frequency (f_max) 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, SiO₂, 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 Ns. 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.

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Narihiko Maeda, Masanobu Hiroki, Noriyuki Watanabe, Yasuhiro Oda, Haruki Yokoyama, Takuma Yagi, Toshiki Makimoto, Takatomo Enoki, and Takashi Kobayashi "Insulator engineering in GaN-based MIS HFETs", Proc. SPIE 6473, Gallium Nitride Materials and Devices II, 647316 (8 February 2007); https://doi.org/10.1117/12.703659

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