Low leakage current in heteroepitaxial Al 0.7 Sc 0.3 N ferroelectric films on Ga N

Yazawa, Keisuke; Evans, Charles; Dickey, Elizabeth C.; Tellekamp, M. Brooks; Brennecka, Geoff L.; Zakutayev, Andriy

doi:10.1103/PhysRevApplied.23.014036

Title: Low leakage current in heteroepitaxial ${Al}_{0.7} {Sc}_{0.3} N$ ferroelectric films on $Ga N$

Journal Article · 17 January 2025 · Physical Review Applied

DOI: https://doi.org/10.1103/PhysRevApplied.23.014036 · OSTI ID:2502112

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Wurtzite $(Al, Sc) N$ ferroelectrics are attractive for microelectronics applications due to their chemical and structural compatibility with wurtzite semiconductors, such as $Ga N$ and $(Al, Ga) N$ . However, the leakage current in epitaxial stacks reported to date should be reduced for reliable device operation. Here, we demonstrate low leakage current in epitaxial ${Al}_{0.7} {Sc}_{0.3} N$ films on $Ga N$ with well-saturated ferroelectric hysteresis loops that are orders of magnitude lower (i.e., 0.07 A ${cm}^{- 2}$ ) than previously reported films (1–19 A ${cm}^{- 2}$ ) having similar or better structural characteristics. We also show that, for these high-quality epitaxial $(Al, Sc) N$ films, structural quality (edge and screw dislocations), as measured by diffraction techniques, is not the dominant contributor to leakage. Instead, the small leakage in our films is limited by thermionic emission across the interfaces, which is distinct from the large leakage due to trap-mediated bulk transport in the previously reported $(Al, Sc) N$ films. To support this conclusion, we show that ${Al}_{0.7} {Sc}_{0.3} N$ on lattice-matched ${In}_{0.18} {Ga}_{0.82} N$ buffers with improved structural characteristics but higher interface roughness exhibit increased leakage characteristics. This demonstration of low leakage current in heteroepitaxial $(Al, Sc) N$ films and understanding of the importance of interface barrier and surface roughness can guide further efforts toward improving the reliability of wurtzite ferroelectric devices. Published by the American Physical Society 2025

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Research Organization:: National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Organization:: Materials Characterization Facility (MCF); National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: AC36-08GO28308

OSTI ID:: 2502112

Report Number(s):: NREL/JA--5K00-89432; 014036

Journal Information:: Physical Review Applied, Journal Name: Physical Review Applied Journal Issue: 1 Vol. 23; ISSN 2331-7019; ISSN PRAHB2

Publisher:: American Physical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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