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Impact of Al profile in high-Al content AlGaN/GaN HEMTs on the 2DEG properties

Papamichail, A. ; Persson, A. R. ; Richter, S. LU ; Stanishev, V. LU ; Armakavicius, N. ; Kühne, P. ; Guo, S. ; Persson, P. O.I. ; Paskov, P. P. and Rorsman, N. , et al. (2024) In Applied Physics Letters 125(12).
Abstract

Ultra-thin high-Al content barrier layers can enable improved gate control and high-frequency operation of AlGaN/GaN high electron mobility transistors (HEMTs) but the precise composition control is very challenging. In this work, we investigate the compositional profiles of AlxGa1−xN/GaN HEMT structures with targeted Al content in the barrier layer, x = 0.50, 0.70, and 1, and thickness in the sub-10 nm range in correlation with the two-dimensional electron gas (2DEG) properties. The HEMT structures are grown by metal-organic chemical vapor deposition on SiC. The maximum Al content in the barrier layer, experimentally determined by scanning transmission electron microscopy combined with energy-dispersive x-ray... (More)

Ultra-thin high-Al content barrier layers can enable improved gate control and high-frequency operation of AlGaN/GaN high electron mobility transistors (HEMTs) but the precise composition control is very challenging. In this work, we investigate the compositional profiles of AlxGa1−xN/GaN HEMT structures with targeted Al content in the barrier layer, x = 0.50, 0.70, and 1, and thickness in the sub-10 nm range in correlation with the two-dimensional electron gas (2DEG) properties. The HEMT structures are grown by metal-organic chemical vapor deposition on SiC. The maximum Al content in the barrier layer, experimentally determined by scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, is found to be lower than that intended and the deviations from the designed structures increase progressively with increasing x. Compositionally sharp interface between GaN and Al0.46Ga0.54N and box-like Al profile is achieved for intended x ∼ 0.50 while pronounced Al grading is found in the samples with intended x of 0.70 and 1, with a maximum Al content of 0.78 reached for the HEMT structure with intended AlN barrier layer. The impact of the experimentally determined Al profiles on the 2DEG properties, obtained by contactless and electrical Hall effect measurements and coupled with self-consistent solution of the Poisson-Schrödinger equation, is evaluated and discussed. It is shown that the observed deviations from the intended Al profiles have a negative effect on the 2DEG confinement and result in reduced mobility parameters, which have significant implications for the implementation of high-Al content AlGaN/GaN structures in high-frequency devices.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Physics Letters
volume
125
issue
12
article number
123505
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:85204926369
ISSN
0003-6951
DOI
10.1063/5.0218911
language
English
LU publication?
yes
id
7a6b2ed0-5379-412e-89c0-7a7dcbb4eedb
date added to LUP
2025-01-08 11:23:35
date last changed
2025-06-23 12:04:35
@article{7a6b2ed0-5379-412e-89c0-7a7dcbb4eedb,
  abstract     = {{<p>Ultra-thin high-Al content barrier layers can enable improved gate control and high-frequency operation of AlGaN/GaN high electron mobility transistors (HEMTs) but the precise composition control is very challenging. In this work, we investigate the compositional profiles of Al<sub>x</sub>Ga<sub>1−x</sub>N/GaN HEMT structures with targeted Al content in the barrier layer, x = 0.50, 0.70, and 1, and thickness in the sub-10 nm range in correlation with the two-dimensional electron gas (2DEG) properties. The HEMT structures are grown by metal-organic chemical vapor deposition on SiC. The maximum Al content in the barrier layer, experimentally determined by scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, is found to be lower than that intended and the deviations from the designed structures increase progressively with increasing x. Compositionally sharp interface between GaN and Al<sub>0.46</sub>Ga<sub>0.54</sub>N and box-like Al profile is achieved for intended x ∼ 0.50 while pronounced Al grading is found in the samples with intended x of 0.70 and 1, with a maximum Al content of 0.78 reached for the HEMT structure with intended AlN barrier layer. The impact of the experimentally determined Al profiles on the 2DEG properties, obtained by contactless and electrical Hall effect measurements and coupled with self-consistent solution of the Poisson-Schrödinger equation, is evaluated and discussed. It is shown that the observed deviations from the intended Al profiles have a negative effect on the 2DEG confinement and result in reduced mobility parameters, which have significant implications for the implementation of high-Al content AlGaN/GaN structures in high-frequency devices.</p>}},
  author       = {{Papamichail, A. and Persson, A. R. and Richter, S. and Stanishev, V. and Armakavicius, N. and Kühne, P. and Guo, S. and Persson, P. O.I. and Paskov, P. P. and Rorsman, N. and Darakchieva, V.}},
  issn         = {{0003-6951}},
  language     = {{eng}},
  number       = {{12}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Applied Physics Letters}},
  title        = {{Impact of Al profile in high-Al content AlGaN/GaN HEMTs on the 2DEG properties}},
  url          = {{http://dx.doi.org/10.1063/5.0218911}},
  doi          = {{10.1063/5.0218911}},
  volume       = {{125}},
  year         = {{2024}},
}