High-Mobility 2DEG at Oxide Interface Enabled by Precise Interface Engineering

06/04/2025 / Announcements

a–c) Sketch of the three different growth approaches to define the interface termination of a BSO/LIO heterostructure. The yellow shaded areas indicate co-deposition growth in an adsorption-controlled growth regime while the red (blue) shaded areas highlight interface termination using layer-by-layer growth. The vertical bars indicate the related shutter-controlled supply of particle flux from the corresponding effusion cell. d) Comparison of RT 2DEG sheet resistance, charge carrier concentration, and mobility to other oxide systems. e) Cross-sectional scanning transmission electron microscopy (STEM) bright field image of the LIO/BSO/DSO heterostructure. f) Enlarged area of the BSO/LIO interface revealing coherent growth of the heterostructure. Atomistic models of BSO and LIO were superimposed to the STEM image using VESTA.

Researchers at the Paul Drude Institute for Solid State Electronics, in collaboration with the Leibniz-Institut für Kristallzüchtung (IKZ); University College London; University of Oxford; and the Deutsches Elektronen-Synchrotron DESY, report the formation of a two-dimensional electron gas (2DEG) with room-temperature electron mobility values up to 119 cm²/Vs at the interface between epitaxial layers of BaSnO₃ (BSO) and LaInO₃ (LIO). This mobility represents the highest value reported to date for a 2DEG in perovskite oxide systems at room temperature. The work, published in Advanced Materials, introduces a molecular beam epitaxy (MBE) growth protocol that enables controlled interface termination, a critical factor in achieving high mobility.

By combining adsorption-controlled co-deposition for bulk layer growth with shutter-controlled, layer-by-layer deposition of interfacial monolayers, the researchers engineered interfaces with specific terminations. Samples with a SnO₂/LaO-terminated interface exhibited reproducible charge carrier accumulation and high electron mobilities, verified through capacitance–voltage profiling and hard X-ray photoelectron spectroscopy. In contrast, heterostructures with BaO/InO₂ termination or undefined terminations did not show comparable electronic properties.

Electrical transport measurements confirmed that the interface termination governs the presence and quality of the 2DEG. SnO₂/LaO-terminated structures consistently yielded low sheet resistance and stable carrier concentrations, with mobility values exceeding 100 cm²/Vs. The study also demonstrated that the accumulation layer can be fully depleted with applied voltage, a feature relevant to potential device integration.

These findings establish interface termination as a key design parameter in oxide heterostructures and demonstrate a reproducible route for achieving high electron mobility in perovskite-based 2DEGs. The approach can be transferred to other perovskite oxide systems and provides a framework for further exploration of buried interfaces in electronic device structures.

Title: Enabling 2D electron gas with high room-temperature electron mobility exceeding 100 cm2 Vs−1 at a perovskite oxide interface
Authors: G. Hoffmann, M. Zupancic, A. A. Riaz, Curran Kalha, C. Schlueter, Andrei Gloskovskii, A. Regoutz, M. Albrecht, J. Nordlander, O. Bierwagen
Source: Adv. Mater., 36, 2409076 (2024)
DOI: 10.1002/adma.202409076

Core Research Area (CReA): Novel Functional Oxide Materials