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AlGaN (2.5%) fully vertical FinFETs : Influence of m- and a-plane substrate alignments

Garigapati, N. S. LU ; Logotheti, A. LU orcid ; So, B. LU orcid ; Malm, J. LU ; Prystawko, P. ; Grzegory, I. ; Nawaz, M. ; Björk, M. ; Darakchieva, V. LU and Lind, E. LU orcid (2026) In Applied Physics Letters 128(11).
Abstract

We demonstrate the first fully vertical single-fin AlGaN FinFETs (Al = 2.5%) on ammonothermal n+-GaN substrates, featuring a gate length of Lg = 200 nm and excellent gate control. This work presents a systematic study of the impact of fin orientation along the a- and m-crystallographic planes on the electrical performance of AlGaN vertical FinFETs. We report that threshold voltage is maximized at fin width, Wfin = 100 nm, with VT = 1.9 V (a-plane) and 1.75 V (m-plane). The highest ON-current density taken at an overdrive voltage VOV = 1.5 V and peak extrinsic transconductance are achieved at Wfin = 200 nm, with JON = 4.4 kA/cm2 (a-plane) and 4.1... (More)

We demonstrate the first fully vertical single-fin AlGaN FinFETs (Al = 2.5%) on ammonothermal n+-GaN substrates, featuring a gate length of Lg = 200 nm and excellent gate control. This work presents a systematic study of the impact of fin orientation along the a- and m-crystallographic planes on the electrical performance of AlGaN vertical FinFETs. We report that threshold voltage is maximized at fin width, Wfin = 100 nm, with VT = 1.9 V (a-plane) and 1.75 V (m-plane). The highest ON-current density taken at an overdrive voltage VOV = 1.5 V and peak extrinsic transconductance are achieved at Wfin = 200 nm, with JON = 4.4 kA/cm2 (a-plane) and 4.1 kA/cm2 (m-plane), and gme,peak = 4.1 kS/cm2 (a-plane) and 3.6 kS/cm2 (m-plane). The minimum specific on-resistance of FinFETs with Wfin = 200 nm, extracted at VOV = 1.5 V, is as follows: RON,sp = 0.85 m Ω cm2 (a-plane) and 0.97 m Ω cm2 (m-plane). The single-fin device area, including current spreading in the drift layer, is used for normalization. Among all variants, a-plane devices with narrower fins delivered the superior electrical performance. These results establish the critical role of crystallographic alignment in optimizing vertical AlGaN device performance and represent a significant step toward scalable vertical AlGaN power transistors.

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; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Physics Letters
volume
128
issue
11
article number
112109
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:105033680583
ISSN
0003-6951
DOI
10.1063/5.0310395
language
English
LU publication?
yes
id
2871eb00-2ccc-485d-8b0f-b7830b830642
date added to LUP
2026-06-08 14:53:00
date last changed
2026-06-08 14:53:57
@article{2871eb00-2ccc-485d-8b0f-b7830b830642,
  abstract     = {{<p>We demonstrate the first fully vertical single-fin AlGaN FinFETs (Al = 2.5%) on ammonothermal n<sup>+</sup>-GaN substrates, featuring a gate length of L<sub>g</sub> = 200 nm and excellent gate control. This work presents a systematic study of the impact of fin orientation along the a- and m-crystallographic planes on the electrical performance of AlGaN vertical FinFETs. We report that threshold voltage is maximized at fin width, W<sub>fin</sub> = 100 nm, with V<sub>T</sub> = 1.9 V (a-plane) and 1.75 V (m-plane). The highest ON-current density taken at an overdrive voltage V<sub>OV</sub> = 1.5 V and peak extrinsic transconductance are achieved at W<sub>fin</sub> = 200 nm, with J<sub>ON</sub> = 4.4 kA/cm<sup>2</sup> (a-plane) and 4.1 kA/cm<sup>2</sup> (m-plane), and g<sub>me,peak</sub> = 4.1 kS/cm<sup>2</sup> (a-plane) and 3.6 kS/cm<sup>2</sup> (m-plane). The minimum specific on-resistance of FinFETs with W<sub>fin</sub> = 200 nm, extracted at V<sub>OV</sub> = 1.5 V, is as follows: R<sub>ON,sp</sub> = 0.85 m Ω cm<sup>2</sup> (a-plane) and 0.97 m Ω cm<sup>2</sup> (m-plane). The single-fin device area, including current spreading in the drift layer, is used for normalization. Among all variants, a-plane devices with narrower fins delivered the superior electrical performance. These results establish the critical role of crystallographic alignment in optimizing vertical AlGaN device performance and represent a significant step toward scalable vertical AlGaN power transistors.</p>}},
  author       = {{Garigapati, N. S. and Logotheti, A. and So, B. and Malm, J. and Prystawko, P. and Grzegory, I. and Nawaz, M. and Björk, M. and Darakchieva, V. and Lind, E.}},
  issn         = {{0003-6951}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{11}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Applied Physics Letters}},
  title        = {{AlGaN (2.5%) fully vertical FinFETs : Influence of m- and a-plane substrate alignments}},
  url          = {{http://dx.doi.org/10.1063/5.0310395}},
  doi          = {{10.1063/5.0310395}},
  volume       = {{128}},
  year         = {{2026}},
}