Band-to-Band Transitions, Selection Rules, Effective Mass, and Excitonic Contributions in Monoclinic β-Ga2O3

Authors

Alyssa Mock, University of Nebraska-Lincoln
Rafal Korlacki, University of Nebraska at LincolnFollow
Chad Briley, University of Nebraska-Lincoln
Vanya Darakchieva, Linkoping University
Bo Monemar, Linkoping University
Yoshinao Kumagai, Tokyo University of Agriculture and Technology
Ken Goto, Tokyo University of Agriculture and Technology
Masataka Higashiwaki, National Institute of Information and Communications Technology
Mathias Schubert, University of Nebraska-LincolnFollow

Date of this Version

2017

Citation

Physical Review B 96, 245205 (2017)

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.96.245205

DOI: 10.1103/PhysRevB.96.245205

Comments

Copyright 2017 by the American Physical Society

Abstract

We employ an eigenpolarization model including the description of direction dependent excitonic effects for rendering critical point structures within the dielectric function tensor of monoclinic β-Ga₂O₃ yielding a comprehensive analysis of generalized ellipsometry data obtained from 0.75–9 eV. The eigenpolarization model permits complete description of the dielectric response. We obtain, for single-electron and excitonic band-to-band transitions, anisotropic critical point model parameters including their polarization vectors within the monoclinic lattice. We compare our experimental analysis with results from density functional theory calculations performed using the Gaussian-attenuation-Perdew-Burke-Ernzerhof hybrid density functional. We present and discuss the order of the fundamental direct band-to-band transitions and their polarization selection rules, the electron and hole effective mass parameters for the three lowest band-to-band transitions, and their excitonic contributions. We find that the effective masses for holes are highly anisotropic and correlate with the selection rules for the fundamental band-to-band transitions. The observed transitions are polarized close to the direction of the lowest hole effective mass for the valence band participating in the transition.