Fully Ion Implanted Normally-Off GaN DMOSFETs with ALD-Al₂O₃ Gate Dielectrics

Michitaka Yoshino; Yuto Ando; Manato Deki; Toru Toyabe; Kazuo Kuriyama; Yoshio Honda; Tomoaki Nishimura; Hiroshi Amano; Tetsu Kachi; Tohru Nakamura

doi:10.3390/ma12050689

Fully Ion Implanted Normally-Off GaN DMOSFETs with ALD-Al₂O₃ Gate Dielectrics

Materials (Basel). 2019 Feb 26;12(5):689. doi: 10.3390/ma12050689.

Authors

Michitaka Yoshino¹, Yuto Ando², Manato Deki³, Toru Toyabe⁴, Kazuo Kuriyama⁵, Yoshio Honda⁶, Tomoaki Nishimura⁷, Hiroshi Amano^{8

9}, Tetsu Kachi¹⁰, Tohru Nakamura^{11

12}

Affiliations

¹ Research Center of Ion Beam Technology, Hosei University, Tokyo 184-8584, Japan. michitaka.yoshino.86@hosei.ac.jp.
² Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8601, Japan. yuuto_a@nuee.nagoya-u.ac.jp.
³ Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan. deki@nuee.nagoya-u.ac.jp.
⁴ Toyo University, Kawagoe 350-8585, Japan. tttoyabe@gmail.com.
⁵ Research Center of Ion Beam Technology, Hosei University, Tokyo 184-8584, Japan. kuri@hosei.ac.jp.
⁶ Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan. honda@nagoya-u.jp.
⁷ Research Center of Ion Beam Technology, Hosei University, Tokyo 184-8584, Japan. t-nishi@hosei.ac.jp.
⁸ Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8601, Japan. amano@nuee.nagoya-u.ac.jp.
⁹ Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan. amano@nuee.nagoya-u.ac.jp.
¹⁰ Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan. kachi@imass.nagoya-u.ac.jp.
¹¹ Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan. tohru@hosei.ac.jp.
¹² Research Center for Micro-Nano Technology, Hosei University, Tokyo 184-0003, Japan. tohru@hosei.ac.jp.

Abstract

A normally-off GaN double-implanted vertical MOSFET (DMOSFET) with an atomic layer deposition (ALD)-Al₂O₃ gate dielectric film on a free-standing GaN substrate fabricated by triple ion implantation is presented. The DMOSFET was formed with Si ion implanted source regions in a Mg ion implanted p-type base with N ion implanted termination regions. A maximum drain current of 115 mA/mm, maximum transconductance of 19 mS/mm at a drain voltage of 15 V, and a threshold voltage of 3.6 V were obtained for the fabricated DMOSFET with a gate length of 0.4 μm with an estimated p-type base Mg surface concentration of 5 × 10¹⁸ cm^-3. The difference between calculated and measured V_ths could be due to the activation ratio of ion-implanted Mg as well as Fermi level pinning and the interface state density. On-resistance of 9.3 mΩ·cm² estimated from the linear region was also attained. Blocking voltage at off-state was 213 V. The fully ion implanted GaN DMOSFET is a promising candidate for future high-voltage and high-power applications.

Keywords: GaN; MOSFET; Mg; Si; ion implantation.