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Phonon properties : Phonon and free charge carrier properties in monoclinic-symmetry β-Ga2O3

Schubert, Mathias LU orcid ; Mock, Alyssa ; Korlacki, Rafał ; Knight, Sean LU ; Monemar, Bo LU ; Goto, Ken LU orcid ; Kumagai, Yoshinao ; Kuramata, Akito ; Galazka, Zbigniew and Wagner, Günther , et al. (2020) In Springer Series in Materials Science 293. p.501-534
Abstract

We present and discuss the complete set of infrared-active phonon modes in monoclinic-symmetry crystal modification gallium oxide (gallia, β-Ga2O3). The phonon mode set is obtained from a comprehensive analysis of generalized spectroscopic ellipsometry data in the farinfrared and infrared spectral regions investigating various n-type electrically conductive single crystal samples with different free electron volume density parameters cut under different orientations. The analysis of the ellipsometry data is performed using an eigendielectric displacement vector summation (EDVS) approach. In this approach, the effect of the free charge carriers onto the lattice modes of intrinsic β-Ga2O3 are... (More)

We present and discuss the complete set of infrared-active phonon modes in monoclinic-symmetry crystal modification gallium oxide (gallia, β-Ga2O3). The phonon mode set is obtained from a comprehensive analysis of generalized spectroscopic ellipsometry data in the farinfrared and infrared spectral regions investigating various n-type electrically conductive single crystal samples with different free electron volume density parameters cut under different orientations. The analysis of the ellipsometry data is performed using an eigendielectric displacement vector summation (EDVS) approach. In this approach, the effect of the free charge carriers onto the lattice modes of intrinsic β-Ga2O3 are removed by calculation. Density functional theory calculations are performed in the general gradient approximation and all phonon modes at the Brillouin-center and their displacement direction dependencies are obtained. Transverse and longitudinal optical phonon mode parameters polarized within the monoclinic plane as well as perpendicular to the monoclinic plane agree excellently between experiment and theory. We also present and discuss the directional limiting frequency parameters within the monoclinic plane, the shape and anisotropy of the reststrahlen band, and the order of the phonon modes in semiconductors with polar phonon modes and monoclinic crystal structure. We further present and discuss the effect of coupling of longitudinal optical phonons with free charge carriers, leading to longitudinal-phonon-plasmon coupled modes. We reveal that the coupled modes, which affect electric and thermal transport, change amplitude, frequency, and direction within the monoclinic plane as a function of free electron concentration. Finally, we show optical Hall effect measurements, and provide experimentally determined effective electron mass parameters in β-Ga2O3 for moderately-doped n-type samples.

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publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
host publication
Gallium Oxide : Materials Properties, Crystal Growth, and Devices - Materials Properties, Crystal Growth, and Devices
series title
Springer Series in Materials Science
editor
Higashiwaki, Masataka and Fujita, Shizuo
volume
293
pages
34 pages
publisher
Springer
external identifiers
  • scopus:85084669681
ISSN
0933-033X
2196-2812
ISBN
978-3-030-37155-5
978-3-030-37153-1
DOI
10.1007/978-3-030-37153-1_28
language
English
LU publication?
no
additional info
Publisher Copyright: © Springer Nature Switzerland AG 2020.
id
0f07eb7f-d102-4880-8f17-5165e5501349
date added to LUP
2025-11-06 16:39:11
date last changed
2025-11-12 03:49:08
@inbook{0f07eb7f-d102-4880-8f17-5165e5501349,
  abstract     = {{<p>We present and discuss the complete set of infrared-active phonon modes in monoclinic-symmetry crystal modification gallium oxide (gallia, β-Ga<sub>2</sub>O<sub>3</sub>). The phonon mode set is obtained from a comprehensive analysis of generalized spectroscopic ellipsometry data in the farinfrared and infrared spectral regions investigating various n-type electrically conductive single crystal samples with different free electron volume density parameters cut under different orientations. The analysis of the ellipsometry data is performed using an eigendielectric displacement vector summation (EDVS) approach. In this approach, the effect of the free charge carriers onto the lattice modes of intrinsic β-Ga<sub>2</sub>O<sub>3</sub> are removed by calculation. Density functional theory calculations are performed in the general gradient approximation and all phonon modes at the Brillouin-center and their displacement direction dependencies are obtained. Transverse and longitudinal optical phonon mode parameters polarized within the monoclinic plane as well as perpendicular to the monoclinic plane agree excellently between experiment and theory. We also present and discuss the directional limiting frequency parameters within the monoclinic plane, the shape and anisotropy of the reststrahlen band, and the order of the phonon modes in semiconductors with polar phonon modes and monoclinic crystal structure. We further present and discuss the effect of coupling of longitudinal optical phonons with free charge carriers, leading to longitudinal-phonon-plasmon coupled modes. We reveal that the coupled modes, which affect electric and thermal transport, change amplitude, frequency, and direction within the monoclinic plane as a function of free electron concentration. Finally, we show optical Hall effect measurements, and provide experimentally determined effective electron mass parameters in β-Ga<sub>2</sub>O<sub>3</sub> for moderately-doped n-type samples.</p>}},
  author       = {{Schubert, Mathias and Mock, Alyssa and Korlacki, Rafał and Knight, Sean and Monemar, Bo and Goto, Ken and Kumagai, Yoshinao and Kuramata, Akito and Galazka, Zbigniew and Wagner, Günther and Tadjer, Marko J. and Wheeler, Virginia D. and Higashiwaki, Masataka and Darakchieva, Vanya}},
  booktitle    = {{Gallium Oxide : Materials Properties, Crystal Growth, and Devices}},
  editor       = {{Higashiwaki, Masataka and Fujita, Shizuo}},
  isbn         = {{978-3-030-37155-5}},
  issn         = {{0933-033X}},
  language     = {{eng}},
  pages        = {{501--534}},
  publisher    = {{Springer}},
  series       = {{Springer Series in Materials Science}},
  title        = {{Phonon properties : Phonon and free charge carrier properties in monoclinic-symmetry β-Ga<sub>2</sub>O<sub>3</sub>}},
  url          = {{http://dx.doi.org/10.1007/978-3-030-37153-1_28}},
  doi          = {{10.1007/978-3-030-37153-1_28}},
  volume       = {{293}},
  year         = {{2020}},
}