Elevated temperature spectroscopic ellipsometry analysis of the dielectric function, exciton, band-to-band transition, and high-frequency dielectric constant properties for single-crystal ZnGa2O4
Abstract
We report the elevated temperature (22 °C ≤ T ≤ 600 °C) dielectric function properties of melt grown single crystal ZnGa2O4 using a spectroscopic ellipsometry approach. A temperature dependent Cauchy dispersion analysis was applied across the transparent spectrum to determine the high-frequency index of refraction yielding a temperature dependent slope of 3.885(2) × 10−5 K−1. A model dielectric function critical point analysis was applied to examine the dielectric function and critical point transitions for each temperature. The lowest energy M0-type critical point associated with the direct bandgap transition in ZnGa2O4 is shown to red-shift linearly as the temperature is increased with a subsequent slope of −0.72(4) meV K−1. Furthermore, increasing the temperature results in a reduction of the excitonic amplitude and increase in the exciton broadening akin to exciton evaporation and lifetime shortening. This matches current theoretical understanding of excitonic behavior and critically provides justification for an anharmonic broadened Lorentz oscillator to be applied for model analysis of excitonic contributions.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 28, 2022
- Source ID
- 10.1063/5.0087623
Entities
People
- Assya Abakar
- Emma Williams
- J. A. Woollam
- Jose Rivera
- K. Irmscher
- Mathias Schubert
- Matthew Hilfiker
- Megan Stokey
- Nate Koeppe
- Rafał Korlacki
- Ufuk Kılıç
- Yousra Traouli
- Zbigniew Galazka
Organizations
- Air Force Office of Scientific Research
- American Chemical Society Petroleum Research Fund
- Leibniz Institute for Crystal Growth
- Linköping University
- National Science Foundation
- University of Angers
- University of Nebraska–Lincoln