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Proceedings Paper

Microwave performance of AlGaN/AlN/GaN-based single and coupled channels HFETs
Author(s): R. A. Ferreyra; X. Li; F. Zhang; C. Zhu; N. Izyumskaya; C. Kayis; V. Avrutin; Ü. Özgür; H. Morkoç
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Paper Abstract

In this work we compare electronic transport performance in HFETs based on single channel (SC) GaN/Al0.30GaN/AlN/GaN (2nm/20nm/1nm/3.5μm) and coupled channel (CC) GaN/Al0.285GaN/AlN/GaN/AlN/GaN (2nm/20nm/1nm/4nm/1nm/3.5μm) structures. The two structures have similar current gain cut-off frequencies (11.6 GHz for SC and 14 GHz for CC for ~ 1μm gate length) however, the maximum drain current, IDmax, is nearly doubled in the CC HFET (0.64 A/mm compared to 0.36 A/mm in SC). HFETs exhibit maximum transconductance (Gmmax) at a bias point close to where maximum f T occurs: VGS =-2.25 V and VDS =12 V and VGS = -2 V and VDS= 15 V for SC and CC HFETs, respectively. Since threshold voltage (Vth) is ~ -3.75 V for both SC and CC structures, devices are able to work at high frequencies with a high gm delivering higher ID. This is in contrast with device performance reported by others where f T is attained at VGS closer to Vth and therefore with lower ID/IDmax ratios and low Gm. Results are consistent in that CC HFET delivers higher IDmax because of the higher electron mobility (μ) and higher carrier density (n) in the channel. As the saturation drain current, IDsat, is attained at electric fields (~40KV/cm) lower than the critical electric field, Ecr , (~ 150KV/cm for GaN ) the higher f T in CC HFETs can be attributed, mainly, to a higher μ, which is in agreement with the Hall measurements. A higher μ in CC HFET is attributed to a shorter hot phonon lifetime.

Paper Details

Date Published: 27 March 2013
PDF: 6 pages
Proc. SPIE 8625, Gallium Nitride Materials and Devices VIII, 86252B (27 March 2013); doi: 10.1117/12.2005165
Show Author Affiliations
R. A. Ferreyra, Virginia Commonwealth Univ. (United States)
X. Li, Virginia Commonwealth Univ. (United States)
F. Zhang, Virginia Commonwealth Univ. (United States)
C. Zhu, Virginia Commonwealth Univ. (United States)
N. Izyumskaya, Virginia Commonwealth Univ. (United States)
C. Kayis, Virginia Commonwealth Univ. (United States)
V. Avrutin, Virginia Commonwealth Univ. (United States)
Ü. Özgür, Virginia Commonwealth Univ. (United States)
H. Morkoç, Virginia Commonwealth Univ. (United States)

Published in SPIE Proceedings Vol. 8625:
Gallium Nitride Materials and Devices VIII
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon; Hiroshi Fujioka, Editor(s)

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