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Electron Trapping and Detrapping in an Oxide Two-Dimensional Electron Gas: The Role of Ferroelastic Twin Walls

Ojha, SK and Hazra, S and Mandal, P and Patel, RK and Nigam, S and Kumar, S and Middey, S (2021) Electron Trapping and Detrapping in an Oxide Two-Dimensional Electron Gas: The Role of Ferroelastic Twin Walls. In: Physical Review Applied, 15 (5).

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Official URL: https://doi.org/10.1103/PhysRevApplied.15.054008


The choice of electrostatic gating over the conventional chemical doping for phase engineering of quantum materials is attributed to the fact that the former can reversibly tune the carrier density without affecting the system's level of disorder. However, this proposition seems to break down in field-effect transistors involving SrTiO3 (STO)-based two-dimensional electron gases. Such peculiar behavior is associated with electron trapping under an external electric field. However, the microscopic nature of the trapping centers remains an open question. In this paper, we investigate electric-field-induced charge-trapping and charge-detrapping phenomena at the conducting interface between the band insulators γ-Al2O3 and STO. Our transport measurements reveal that the charge trapping under a positive back-gate voltage (Vg) above the tetragonal-to-cubic structural transition temperature (Tc) of STO has a contribution from electric-field-assisted thermal escape of electrons from the quantum well, and from clustering of oxygen vacancies as well. We observe an additional source of trapping below Tc, which arises from the trapping of free carriers at ferroelastic twin walls in the STO. Application of a negative Vg results in charge detrapping, which vanishes above Tc. This feature demonstrates the crucial role of structural domain walls in the electrical transport properties of STO-based heterostructures. The number of charges trapped (detrapped) at (from) a twin wall is controlled by the net polarity of the wall and is completely reversible with a sweep of Vg. © 2021 American Physical Society.

Item Type: Journal Article
Publication: Physical Review Applied
Publisher: American Physical Society
Additional Information: The copyright for this article belongs to Authors
Keywords: Alumina; Aluminum oxide; Charge trapping; Domain walls; Electric fields; Electron traps; Electrons; Field effect transistors; Quantum chemistry; Semiconductor quantum wells; Strontium titanates; Titanium compounds, Back-gate voltages; Conducting interface; Electric field induced; Electrical transport properties; External electric field; Structural domains; Structural transition temperature; Transport measurements, Two dimensional electron gas
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 17 Aug 2021 10:45
Last Modified: 17 Aug 2021 10:45
URI: http://eprints.iisc.ac.in/id/eprint/69175

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