First-principles simulations of excited states, using density-functional and many-body perturbation theory, are now capable of accurately predicting electronic and optical properties of complex oxides, enabling unprecedented understanding and computational materials design. After briefly discussing these techniques and their numerical implementation, I will focus on their application to Ga2O3. This material is interesting for transparent electronics in the semiconductor industry since it conducts electrical current while being transparent at the same time.
For Ga2O3 I will provide an overview of recent efforts by several groups to understand the optical absorption in terms of quasiparticle electronic structure and optical transition-matrix elements. These studies provide a clear quantitative picture of the optical anisotropy. I will then show how excitonic effects influence the spectrum close to the absorption onset and at high photon energies. In order to achieve an accurate computational description of excitons, the electron-hole interaction needs to be taken into account. To this end it is mandatory to understand the influence of dielectric screening, which is a long-standing problem in computational materials science. I will explain how the presence of free carriers and of lattice polarization contributes to dielectric screening, impacting the electron-hole interaction, with consequences for optical spectra.
Finally, I will also allude to the computational infrastructure needed to compute these highly accurate theoretical spectra for Ga2O3, since, more generally, combining numerical approaches with cutting-edge computation allows to further develop computational materials science and to perform highly accurate theoretical spectroscopy for modern, complex materials that drive societal progress.
André Schleife, "Optical properties of Ga2O3 from first principles: excitons, free-carriers, and dielectric screening (Conference Presentation)," Proc. SPIE 10533, Oxide-based Materials and Devices IX, 1053305 (Presented at SPIE OPTO: January 28, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2292770.5751531047001.
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