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SSEP Seminar: Computational studies of ultrawide band gap semiconductors: Ga2O3 and LiGaO2

Friday, November 13, 2020, 12:00 am


Title:                 Computational studies of ultrawide band gap semiconductors: Ga2O3 and LiGaO2

Speaker:           Prof. Walter Lambrecht, Department of Physics, Case Western Reserve University

Date:                 Friday November 13, 2020

Time talk:         12 pm (noon) – 1 pm

Gathering:        2 pm – 3 pm

Location:          Zoom

Abstract: Ga2O3 in the beta structure is now widely studied as an ultrawide band gap semiconductor. I will present our results on modeling electron paramagnetic resonance spectra in β-Ga2O3. Two EPR spectra are related to Ga vacancies, one occurs only after optical or X-ray excitation. Calculations of the hyperfine and g-tensors help to identify which signal corresponds to which vacancy structure.  I will also discuss the EPR spectra of Mg and Zn dopants in Ga2O3. Most of the talk, however, will be about introducing two potential new ultrawide gap semiconductors, LiGaO2 and NaGaO2. LiGaO2, has been studied in the past as ceramic and piezoelectric material but we recently showed it should be possible to n-type dope it with Si or Ge. I will present results on the native defects and various dopants in LiGaO2 as well as a study of the EPR parameters of the Li and Ga vacancies, which have already been measured. I will also present GW band structure calculations, showing that LiGaO2 and NaGaO2 both have a wurtzite derived structure with gaps larger than 5.5 eV but have nonetheless interesting differences in  the valence band maximum splitting which result in anisotropic absorption onsets. Finally, I will also discuss alternative structures of these materials, which occur at high pressure.

Biography: Walter Lambrecht did his PhD in Physics at Ghent University in Belgium in 1980. After a visiting professorship in Bahía Blanca, Argentina (1982-84)  and a postdoc at the Max Planck Institute for Solid State Research in Stuttgart (1984-1987), he joined Case Western Reserve University as a researcher and became a faculty member there in 1996. He is a Fellow of the APS (2002) and was awarded the Faculty Distinguished Research Award of CWRU in 2018.  He works on electronic structure of a broad range of materials.


Gathering: We know that it is hard to build your own network and discuss about research with experts around the world during a global pandemic. Hence, we want to give you the possibility to schedule your own coffee break discussion with our guests. Please, reach out to me ( to plan your private session of about 10-15 min. You can use this time to ask more questions or present your work, and hopefully new collaborations can arise from this.

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