Defect states in the electronic structure of Ga2O3 transparent conductive oxides

Published

June 23, 2026

Author(s)

Elizaveta Pyatenko, Constantin Wansorra, Ralph Steininger, John Vinson, Wolfram Witte, Dimitrios Hariskos, Michael Powalla, Clemens Heske, Lothar Weinhardt, Dirk Hauschild

Abstract

Defect states are crucial in many electronic devices. Oxygen vacancies, for example, are common in transparent conductive oxides and can both be beneficial (e.g., as dopant to enhance conductivity) as well as detrimental (e.g., leading to reduced device performance by recombination at interfaces). Using soft and hard x-ray photoelectron spectroscopy (PES and HAXPES) with excitation photon energies ranging from 0.1 keV to 6.3 keV, we study the electronic surface structure of differently processed Ga2O3 samples in a depth-resolved fashion. Specifically, we investigate a Ga2O3 thin film, as used in Cu(In,Ga)Se2-based thin-film solar cells, as well as a β-Ga2O3 single crystal before and after a defect-inducing Ar+-ion treatment. Spectra calculations based on density functional theory (DFT) are used to explain the PES and HAXPES valence band signatures as a function of the excitation photon energy. The β-Ga2O3 single crystal spectra can be well described by the DFT calculations. In contrast, the Ga2O3 thin film and Ar+-ion treated β-Ga2O3 show significant spectral broadening of the valence band features and additional spectral intensity close to the valence band maximum, which we assign to defect states. This additional intensity varies as a function of probing depth, suggesting that these defects are mostly localized at the surface. We also discuss the importance of DFT-based spectra calculations to verify the proper determination of valence band maxima using a linear extrapolation.

Citation

Journal of Physical Chemistry C

Volume

130

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.jpcc.6c02301

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Citation

Pyatenko, E. , Wansorra, C. , Steininger, R. , Vinson, J. , Witte, W. , Hariskos, D. , Powalla, M. , Heske, C. , Weinhardt, L. and Hauschild, D. (2026), Defect states in the electronic structure of Ga2O3 transparent conductive oxides, Journal of Physical Chemistry C, [online], https://doi.org/10.1021/acs.jpcc.6c02301, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=961325 (Accessed July 14, 2026)

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