Exploring Optical and Electronic Properties of Chromium Defects in β-Ga<sub>2</sub>O<sub>3</sub>

ORAL

Abstract

β-Ga₂O₃ is a promising material for power electronics and ultraviolet (UV) optoelectronics due to its ultra-wide bandgap (~4.9 eV), high breakdown voltage, and thermal stability. Its capacity to host defects and dopants allows tunable properties, making it suitable for high-power and quantum applications. However, understanding and controlling these defects, particularly transition metal impurities like chromium (Cr), is crucial for optimizing material and device performance. Here, we investigate Cr impurities in β-Ga₂O₃ using photoluminescence (PL) spectroscopy at cryogenic temperatures and density functional theory calculations. Our PL measurements reveal a sharp ensemble emission from Cr defects with a zero-phonon line (ZPL) at 1.79 eV and a series of peaks at lower energies attributed to complex phonon sideband signatures, similar to Cr emissions in Al₂O₃. Polarization-dependent PL shows that while the PL intensity of the ZPL and sidebands share the same variations with excitation polarization angle, they exhibit different emission polarization angles—an observation that deviates from the Franck-Condon approximation. Simulated PL lineshapes agree with experimental data, providing insights into electron-phonon interactions and the observed deviations from expected behavior. This comprehensive study enhances our understanding of Cr-related defects in β-Ga₂O₃, paving the way for advancements in both classical power devices and emerging solid-state quantum technologies.

*This work was supported via the UC Santa Barbara National Science Foundation (NSF) Quantum Foundry funded via the Q-AMASE-i program under award DMR-1906325. MET was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, and Co-design Center for Quantum Advantage (C2QA) under contract number DE-SC0012704. SM was supported by the GAME MURI of the Air Force Office of Scientific Research (FA9550-18-1-0479). CVdW acknowledges a Vannevar Bush Faculty Fellowship (Office of Naval Research Award No. N00014-22-1-2808). Use was made of computational facilities purchased with funds from the NSF (CNS-1725797) and administered by the Center for Scientific Computing (CSC). The CSC is supported by the California NanoSystems Institute and the Materials Research Science and Engineering Center (MRSEC; NSF DMR 2308708) at UC Santa Barbara. This work used Bridges-2 at PSC through allocation DMR070069 from the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by National Science Foundation grant number #1548562.

–

Presenters

  • Sahil Patel

    • Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106-5080, U.S.A.
    • University of California, Santa Barbara

Authors

  • Mark E Turiansky

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.

  • Sai Mu

    • University of South Carolina
    • Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina, 29208, U.S.A.

  • Lukas Razinkovas

    • Center for Physical Sciences and Technology (FTMC), Vilnius LT–10257, Lithuania

  • Kamyar Parto

    • Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106-5080, U.S.A.
    • University of California, Santa Barbara

  • Sahil Patel

    • Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106-5080, U.S.A.
    • University of California, Santa Barbara

  • Sean Doan

    • Department of Physics, University of California, Santa Barbara, CA 93106-9530, U.S.A.
    • University of California, Santa Barbara

  • Ganesh Pokharel

    • Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.
    • University of California, Santa Barbara

  • Steven J Gomez Alvarado

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.

  • Stephen D Wilson

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.
    • University of California at Santa Babara

  • Galan Moody

    • Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106-5080, U.S.A.
    • University of California, Santa Barbara

  • Chris G Van de Walle

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara, CA 93106-5050, U.S.A.