Anisotropic dielectric functions, band-to-band transitions, and critical points in α -Ga2O3
Abstract
We use a combined generalized spectroscopic ellipsometry and density functional theory approach to determine and analyze the anisotropic dielectric functions of an α-Ga2O3 thin film. The sample is grown epitaxially by plasma-assisted molecular beam epitaxy on m-plane sapphire. Generalized spectroscopic ellipsometry data from multiple sample azimuths in the spectral range from 0.73 eV to 8.75 eV are simultaneously analyzed. Density functional theory is used to calculate the valence and conduction band structure. We identify, for the indirect-bandgap material, two direct band-to-band transitions with M0-type van Hove singularities for polarization perpendicular to the c axis, E0,⊥=5.46(6) eV and E0,⊥=6.04(1) eV, and one direct band-to-band transition with M1-type van Hove singularity for polarization parallel to E0,||=5.44(2) eV. We further identify excitonic contributions with a small binding energy of 7 meV associated with the lowest ordinary transition and a hyperbolic exciton at the M1-type critical point with a large binding energy of 178 meV.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 08, 2021
- Source ID
- 10.1063/5.0031424
Entities
People
- Debdeep Jena
- Huili Grace Xing
- J. A. Woollam
- Mathias Schubert
- Matthew Hilfiker
- Megan Stokey
- Rafał Korlacki
- Riena Jinno
- Ufuk Kılıç
- Yong-Jin Cho
Organizations
- Air Force Office of Scientific Research
- American Chemical Society Petroleum Research Fund
- Cornell University
- Kyoto University
- Linköping University
- National Science Foundation
- University of Nebraska–Lincoln