Dielectric Function Tensor (1.5 eV to 9.0 eV), Anisotropy, and Band to Band Transitions of Monoclinic β-(Al_xGa_1–x)₂O₃ (x ≤ 0.21) Films

Authors

Matthew Hilfiker, University of Nebraska-LincolnFollow
Ufuk Kilic, University of Nebraska-LincolnFollow
Alyssa Mock, Linköping UniversityFollow
Vanya Darakchieva, Linköping University, SwedenFollow
Sean Knight, University of Nebraska-LincolnFollow
Rafal Korlacki, University of Nebraska-LincolnFollow
Akhil Mauze, University of California, Santa Barbara
Yuewei Zhang, University of California, Santa Barbara
James Speck, University of California, Santa Barbara
Mathias SchubertFollow

ORCID IDs

Matthew Hilfiker https://orcid.org/0000-0002-7015-5484

Ufuk Kilic https://orcid.org/0000-0002-4235-3002

Alyssa Mock https://orcid.org/0000-0002-4235-3002

Vanya Darakchieva https://orcid.org/0000-0002-8112-7411

Sean Knight https://orcid.org/0000-0002-2758-6967

Rafał Korlacki https://orcid.org/0000-0003-3989-2731

Akhil Mauze https://orcid.org/0000-0003-4503-2455

Yuewei Zhang https://orcid.org/0000-0002-4192-1442

Mathias Schubert https://orcid.org/0000-0001-6238-663X

Document Type

Article

Date of this Version

6-2019

Citation

Applied Physics Letters 114, 231901 (2019)

DOI: 10.1063/1.5097780

Comments

Copyright 2019 by AIP Publishing

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Applied Physics Letters 114, 231901 (2019) and may be found at https://doi.org/10.1063/1.5097780

Abstract

A set of monoclinic β-(Al_xGa_1–x)₂O₃ films coherently grown by plasma-assisted molecular beam epitaxy onto (010)-oriented β-Ga₂O₃ substrates for compositions x ≤ 0.21 is investigated by generalized spectroscopic ellipsometry at room temperature in the spectral range of 1.5 eV–9.0 eV. We present the composition dependence of the excitonic and band to band transition energy parameters using a previously described eigendielectric summation approach for β-Ga₂O₃ from the study by Mock et al. All energies shift to a shorter wavelength with the increasing Al content in accordance with the much larger fundamental band to band transition energies of Al₂O₃ regardless of crystal symmetry. The observed increase in the lowest band to band transition energy is in excellent agreement with recent theoretical predictions. The most important observation is that charge confinement in heterostructures will strongly depend on the growth condition due to the strongly anisotropic properties of the band to band transitions.