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Optimization of GaN Nanowires Reformation Process by Metalorganic Chemical Vapor Deposition for Device-Quality GaN Templates

Delgado Carrascon, Rosalia ; Tran, Dat Quoc ; Sukkaew, Pitsiri ; Mock, Alyssa ; Ciechonski, Rafal ; Ohlsson, Jonas LU ; Zhu, Yadan ; Hultin, Olof LU ; Monemar, Bo LU and Paskov, Plamen P. , et al. (2020) In Physica Status Solidi (B) Basic Research 257(4).
Abstract

Herein, the potential of reformed GaN nanowires (NWs) fabricated by metalorganic chemical vapor deposition (MOCVD) for device-quality low-defect density templates and low-cost alternative to bulk GaN substrates is demonstrated. The effects of epilayer thickness and NW reformation conditions on the crystalline quality and thermal conductivity of the subsequent GaN epilayers are investigated. Smooth surfaces with atomically step-like morphologies with no spirals are achieved for GaN epilayers on the reformed NW templates, indicating step-flow growth mode. It is further found that annealing of the NWs at a temperature of 1030 °C in the presence of NH3 and H2, followed by a coalescence done at the same temperature... (More)

Herein, the potential of reformed GaN nanowires (NWs) fabricated by metalorganic chemical vapor deposition (MOCVD) for device-quality low-defect density templates and low-cost alternative to bulk GaN substrates is demonstrated. The effects of epilayer thickness and NW reformation conditions on the crystalline quality and thermal conductivity of the subsequent GaN epilayers are investigated. Smooth surfaces with atomically step-like morphologies with no spirals are achieved for GaN epilayers on the reformed NW templates, indicating step-flow growth mode. It is further found that annealing of the NWs at a temperature of 1030 °C in the presence of NH3 and H2, followed by a coalescence done at the same temperature under planar growth conditions, leads to the most efficient screw dislocation density reduction by nearly an order of magnitude. At these optimized conditions, the growth takes place in a layer-by-layer fashion, producing a smooth surface with a root mean square (RMS) roughness of 0.12 nm. The highest thermal conductivity of k = 206 W m−1 K−1, approaching the respective value of bulk GaN, is obtained for the optimized 2 μm-thick GaN layer. The thermal conductivity results are further discussed in terms of the phonon-dislocation and the phonon-boundary scattering.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
dislocation densities, GaN, nanowires, thermal conductivity
in
Physica Status Solidi (B) Basic Research
volume
257
issue
4
article number
1900581
publisher
John Wiley and Sons
external identifiers
  • scopus:85076421200
ISSN
0370-1972
DOI
10.1002/pssb.201900581
language
English
LU publication?
yes
id
173e8982-409a-4d53-a570-cd6446259f1f
date added to LUP
2020-01-10 11:54:46
date last changed
2021-01-06 08:09:23
@article{173e8982-409a-4d53-a570-cd6446259f1f,
  abstract     = {<p>Herein, the potential of reformed GaN nanowires (NWs) fabricated by metalorganic chemical vapor deposition (MOCVD) for device-quality low-defect density templates and low-cost alternative to bulk GaN substrates is demonstrated. The effects of epilayer thickness and NW reformation conditions on the crystalline quality and thermal conductivity of the subsequent GaN epilayers are investigated. Smooth surfaces with atomically step-like morphologies with no spirals are achieved for GaN epilayers on the reformed NW templates, indicating step-flow growth mode. It is further found that annealing of the NWs at a temperature of 1030 °C in the presence of NH<sub>3</sub> and H<sub>2</sub>, followed by a coalescence done at the same temperature under planar growth conditions, leads to the most efficient screw dislocation density reduction by nearly an order of magnitude. At these optimized conditions, the growth takes place in a layer-by-layer fashion, producing a smooth surface with a root mean square (RMS) roughness of 0.12 nm. The highest thermal conductivity of k = 206 W m<sup>−1</sup> K<sup>−1</sup>, approaching the respective value of bulk GaN, is obtained for the optimized 2 μm-thick GaN layer. The thermal conductivity results are further discussed in terms of the phonon-dislocation and the phonon-boundary scattering.</p>},
  author       = {Delgado Carrascon, Rosalia and Tran, Dat Quoc and Sukkaew, Pitsiri and Mock, Alyssa and Ciechonski, Rafal and Ohlsson, Jonas and Zhu, Yadan and Hultin, Olof and Monemar, Bo and Paskov, Plamen P. and Samuelson, Lars and Darakchieva, Vanya},
  issn         = {0370-1972},
  language     = {eng},
  number       = {4},
  publisher    = {John Wiley and Sons},
  series       = {Physica Status Solidi (B) Basic Research},
  title        = {Optimization of GaN Nanowires Reformation Process by Metalorganic Chemical Vapor Deposition for Device-Quality GaN Templates},
  url          = {http://dx.doi.org/10.1002/pssb.201900581},
  doi          = {10.1002/pssb.201900581},
  volume       = {257},
  year         = {2020},
}