基板工学によるパワーエレクトロニクスの進歩(NREL Researchers Advance Substrate Engineering Pathways To Improve Power Electronics)

2025-03-17 米国国立再生可能エネルギー研究所（NREL）

＜関連情報＞

• https://www.nrel.gov/news/program/2025/nrel-researchers-advance-substrate-engineering-pathways-to-improve-power-electronics.html
• https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.22.054044
• https://journals.aps.org/prxenergy/abstract/10.1103/PRXEnergy.3.033007

超ワイドギャップ窒化物の第一原理からのヘテロ構造界面工学： TaC/AlNおよびTaC/GaN岩塩-ウルツ鉱界面 Heterostructural interface engineering for ultrawide-gap nitrides from first principles: Ta⁢C/Al⁢N and Ta⁢C/Ga⁢N rocksalt-wurtzite interfaces

Sharad Mahatara and Stephan Lany
Physical Review Applied  Published: 15 November, 2024
DOI:https://doi.org/10.1103/PhysRevApplied.22.054044

Abstract

Epitaxial lattice matching is an important condition for the formation of coherent interfaces with low defect densities. However, lattice-matched substrates with the same crystal structure as the active layer are often not available, suggesting opportunities for utilizing heterostructural interfaces. For example, at high Al contents that are interesting for ultrawide-gap applications in power electronics, Al⁢Ga₁₋⁢N semiconductor alloys in the (0001) orientation of the wurtzite (wz) structure become lattice-matched to (111)-oriented rocksalt (rs) Ta⁢C substrates. To predict the expected interface atomic structures under different synthesis conditions, we perform high-throughput density-functional-theory calculations, using an algorithm for systematic sampling of the possible stacking sequences of the atomic layers on the in-plane hexagonal lattice. The approach considers octahedral, tetrahedral, and prismatic coordination motifs, and is generally applicable for the modeling of commensurate rs/wz heterostructural interfaces. Our results provide guidance for synthesis control of substrate-film bonding and the polarity of ultrawide-gap Al⁢Ga₁₋⁢N alloys on Ta⁢C substrates.

縦型AlGa1-Nパワーエレクトロニクス・デバイスのためのTaC仮想基板の設計 Designing Ta⁢C Virtual Substrates for Vertical Al⁢Ga1−⁢N Power Electronics Devices

Dennice M. Roberts, Jordan A. Hachtel, Nancy M. Haegel, Moira K. Miller, Anthony D. Rice, and M. Brooks Tellekamp
PRX Energy Published: 27 September, 2024
DOI:https://doi.org/10.1103/PRXEnergy.3.033007

Abstract

Power electronics are critical for a sustainable energy future, playing a key role in electrification and integration of renewable energy sources into the grid. Advances in ultrawide band gap materials are needed to handle higher powers in smaller form factors while reducing electrical and thermal losses. High Al content Al⁢Ga_1−⁢N is theoretically capable of meeting these demands, but its impact in power electronics has been severely restricted by a lack of substrates that can satisfy conductivity, lattice matching, and/or thermal expansion requirements. We demonstrate that electrically conductive Ta⁢C can be used as a virtual substrate for Al⁢Ga_1−⁢N heteroepitaxy. Scaleably sputtered Ta⁢C grown on Al₂⁢O₃, followed by high-temperature face-to-face annealing, produces a thin film Ta⁢C template with an effective hexagonal lattice constant matched to Al_0.70⁢Ga_0.30⁢N. Annealing of the Ta⁢C promotes recrystallization, significantly improving crystallinity and reducing crystalline defects from as-deposited columnar grains to a step-and-terrace surface morphology, enabling the subsequent growth of high-quality Al_0.70⁢Ga_0.30⁢N by molecular beam epitaxy. X-ray diffraction and scanning transmission electron microscopy confirm that the Al⁢Ga₁₋⁢N layer is heteroepitaxially aligned, strain-free, and lattice-matched, transitioning abruptly from Ta⁢C to Al⁢Ga _−⁢N without intermediate phases. These results demonstrate Ta⁢C virtual substrates as electrically conductive, lattice-matched, and thermally compatible templates for vertical Al⁢Ga₁₋⁢N devices that can meet the growing power needs of a sustainable energy future.