Infrared-active phonon modes and static dielectric constants in α-(AlxGa1−x)2O3 (0.18 ≤ x ≤ 0.54) alloys
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 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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 14, 2022
- Source ID
- 10.1063/5.0085958
Entities
People
- Debdeep Jena
- Huili Grace Xing
- Mathias Schubert
- Matthew Hilfiker
- Megan Stokey
- Rafał Korlacki
- Riena Jinno
- Sean Knight
- Steffen Richter
- Teresa Gramer
- Vanya Darakchieva
- Yong-Jin Cho
Organizations
- Air Force Office of Scientific Research
- Cornell University
- Japan Society for the Promotion of Science
- Knut and Alice Wallenberg Foundation
- Kyoto University
- Linköping University
- Lund University
- National Science Foundation
- Swedish Energy Agency
- Swedish Foundation for Strategic Research
- Swedish Governmental Agency for Innovation Systems
- Swedish Research Council
- University of Nebraska–Lincoln