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Infrared-active phonon modes and static dielectric constants in -(AlxGa 1-x)2O3(0.18 ≤ x ≤ 0.54) alloys

Stokey, Megan ; Gramer, Teresa ; Korlacki, Rafał ; Knight, Sean ; Richter, Steffen LU ; Jinno, Riena ; Cho, Yongjin ; Xing, Huili Grace ; Jena, Debdeep and Hilfiker, Matthew , et al. (2022) In Applied Physics Letters 120(11).
Abstract

We determine the composition dependence of the transverse and longitudinal optical infrared-active phonon modes in rhombohedral α-(AlxGa1-x)2O3 alloys by far-infrared and infrared generalized spectroscopic ellipsometry. Single-crystalline high quality undoped thin-films grown on m-plane oriented α-Al2O3 substrates with x = 0.18, 0.37, and 0.54 were investigated. A single mode behavior is observed for all phonon modes, i.e., their frequencies shift gradually between the equivalent phonon modes of the isostructural binary parent compounds. We also provide physical model line shape functions for the anisotropic dielectric functions. We use the anisotropic high-frequency dielectric constants for polarizations parallel and perpendicular to... (More)

We determine the composition dependence of the transverse and longitudinal optical infrared-active phonon modes in rhombohedral α-(AlxGa1-x)2O3 alloys by far-infrared and infrared generalized spectroscopic ellipsometry. Single-crystalline high quality undoped thin-films grown on m-plane oriented α-Al2O3 substrates with x = 0.18, 0.37, and 0.54 were investigated. A single mode behavior is observed for all phonon modes, i.e., their frequencies shift gradually between the equivalent phonon modes of the isostructural binary parent compounds. We also provide physical model line shape functions for the anisotropic dielectric functions. We use the anisotropic high-frequency dielectric constants for polarizations parallel and perpendicular to the lattice c axis measured recently by Hilfiker et al. [Appl. Phys. Lett. 119, 092103 (2021)], and we determine the anisotropic static dielectric constants using the Lyddane-Sachs-Teller relation. The static dielectric constants can be approximated by linear relationships between those of α-Ga2O3 and α-Al2O3. The optical phonon modes and static dielectric constants will become useful for device design and free charge carrier characterization using optical techniques.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Applied Physics Letters
volume
120
issue
11
article number
112202
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:85126835203
ISSN
0003-6951
DOI
10.1063/5.0085958
language
English
LU publication?
yes
id
5b88d841-3c68-479b-ae9c-800a13834f36
date added to LUP
2022-04-19 14:28:41
date last changed
2023-11-08 21:54:42
@article{5b88d841-3c68-479b-ae9c-800a13834f36,
  abstract     = {{<p>We determine the composition dependence of the transverse and longitudinal optical infrared-active phonon modes in rhombohedral α-(AlxGa1-x)2O3 alloys by far-infrared and infrared generalized spectroscopic ellipsometry. Single-crystalline high quality undoped thin-films grown on m-plane oriented α-Al2O3 substrates with x = 0.18, 0.37, and 0.54 were investigated. A single mode behavior is observed for all phonon modes, i.e., their frequencies shift gradually between the equivalent phonon modes of the isostructural binary parent compounds. We also provide physical model line shape functions for the anisotropic dielectric functions. We use the anisotropic high-frequency dielectric constants for polarizations parallel and perpendicular to the lattice c axis measured recently by Hilfiker et al. [Appl. Phys. Lett. 119, 092103 (2021)], and we determine the anisotropic static dielectric constants using the Lyddane-Sachs-Teller relation. The static dielectric constants can be approximated by linear relationships between those of α-Ga2O3 and α-Al2O3. The optical phonon modes and static dielectric constants will become useful for device design and free charge carrier characterization using optical techniques.</p>}},
  author       = {{Stokey, Megan and Gramer, Teresa and Korlacki, Rafał and Knight, Sean and Richter, Steffen and Jinno, Riena and Cho, Yongjin and Xing, Huili Grace and Jena, Debdeep and Hilfiker, Matthew and Darakchieva, Vanya and Schubert, Mathias}},
  issn         = {{0003-6951}},
  language     = {{eng}},
  number       = {{11}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Applied Physics Letters}},
  title        = {{Infrared-active phonon modes and static dielectric constants in -(Al<sub>x</sub>Ga <sub>1-x</sub>)<sub>2</sub>O<sub>3</sub>(0.18 ≤ x ≤ 0.54) alloys}},
  url          = {{http://dx.doi.org/10.1063/5.0085958}},
  doi          = {{10.1063/5.0085958}},
  volume       = {{120}},
  year         = {{2022}},
}