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Impact of AlN buffer thickness on electrical and thermal characteristics of AlGaN/GaN/AlN HEMTs

Kim, Minho ; Tran, Dat Q. ; Paskov, Plamen P. ; Choi, Uiho ; Nam, Okhyun and Darakchieva, Vanya LU (2026) In Applied Physics Letters 128(4).
Abstract

We investigate the influence of AlN buffer thickness on the structural, electrical, and thermal properties of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates by metal-organic chemical vapor deposition. X-ray diffraction and atomic force microscopy reveal that while thin AlN layers (120 nm) exhibit compressive strain and smooth step-flow surfaces, thicker single-layer buffers (550 nm) develop tensile strain and increased surface roughness. Multi-layer buffer structures up to 2 μ m alleviate strain and maintain surface integrity. Low-temperature Hall measurements confirm that electron mobility decreases with increasing interface roughness, with the highest mobility observed in the structure... (More)

We investigate the influence of AlN buffer thickness on the structural, electrical, and thermal properties of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates by metal-organic chemical vapor deposition. X-ray diffraction and atomic force microscopy reveal that while thin AlN layers (120 nm) exhibit compressive strain and smooth step-flow surfaces, thicker single-layer buffers (550 nm) develop tensile strain and increased surface roughness. Multi-layer buffer structures up to 2 μ m alleviate strain and maintain surface integrity. Low-temperature Hall measurements confirm that electron mobility decreases with increasing interface roughness, with the highest mobility observed in the structure with a thin AlN buffer. Transient thermoreflectance measurements show that thermal conductivity (ThC) of the AlN buffer increases with the thickness, reaching 190 W/m.K at 300 K for the 2 μ m buffer layer, which is approximately 60% of the bulk AlN ThC value. These results highlight the importance of optimizing AlN buffer design to balance strain relaxation, thermal management, and carrier transport for high-performance GaN-based HEMTs.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Physics Letters
volume
128
issue
4
article number
042105
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:105028973179
ISSN
0003-6951
DOI
10.1063/5.0310464
language
English
LU publication?
yes
id
09d8d6c5-4ace-4f67-be3b-4e44a8a82874
date added to LUP
2026-02-19 13:51:59
date last changed
2026-02-19 13:53:09
@article{09d8d6c5-4ace-4f67-be3b-4e44a8a82874,
  abstract     = {{<p>We investigate the influence of AlN buffer thickness on the structural, electrical, and thermal properties of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates by metal-organic chemical vapor deposition. X-ray diffraction and atomic force microscopy reveal that while thin AlN layers (120 nm) exhibit compressive strain and smooth step-flow surfaces, thicker single-layer buffers (550 nm) develop tensile strain and increased surface roughness. Multi-layer buffer structures up to 2 μ m alleviate strain and maintain surface integrity. Low-temperature Hall measurements confirm that electron mobility decreases with increasing interface roughness, with the highest mobility observed in the structure with a thin AlN buffer. Transient thermoreflectance measurements show that thermal conductivity (ThC) of the AlN buffer increases with the thickness, reaching 190 W/m.K at 300 K for the 2 μ m buffer layer, which is approximately 60% of the bulk AlN ThC value. These results highlight the importance of optimizing AlN buffer design to balance strain relaxation, thermal management, and carrier transport for high-performance GaN-based HEMTs.</p>}},
  author       = {{Kim, Minho and Tran, Dat Q. and Paskov, Plamen P. and Choi, Uiho and Nam, Okhyun and Darakchieva, Vanya}},
  issn         = {{0003-6951}},
  language     = {{eng}},
  number       = {{4}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Applied Physics Letters}},
  title        = {{Impact of AlN buffer thickness on electrical and thermal characteristics of AlGaN/GaN/AlN HEMTs}},
  url          = {{http://dx.doi.org/10.1063/5.0310464}},
  doi          = {{10.1063/5.0310464}},
  volume       = {{128}},
  year         = {{2026}},
}