The Dawn of a New Era in Power Semiconductors: Nagoya University's Ga₂O₃ Breakthrough

Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, is poised to revolutionize power electronics with its exceptional properties. Researchers at Nagoya University have just unveiled six pivotal advances in Ga₂O₃ processing, addressing longstanding challenges in thin-film growth and device fabrication. This work, presented at the 73rd JSAP Spring Meeting in March 2026, marks a significant step toward commercializing next-generation power devices for electric vehicles (EVs), renewable energy systems, and space applications.

Leading the charge is Professor Masaru Hori from Nagoya University's Center for Low-temperature Plasma Sciences (cLPS), in collaboration with spinout company NU-Rei Co., Ltd. Their innovations promise devices that operate at higher voltages, with superior efficiency and lower costs compared to traditional silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) alternatives. As Japan solidifies its position as a global leader in semiconductor research, this breakthrough underscores the vital role of universities in driving technological innovation.

What Makes Gallium Oxide (Ga₂O₃) a Game-Changer?

Gallium oxide, or β-Ga₂O₃ in its most stable beta phase, boasts a bandgap of approximately 4.8 electron volts (eV)—far wider than silicon's 1.1 eV, SiC's 3.2 eV, or GaN's 3.4 eV. This translates to a critical electric field strength of up to 8 megavolts per centimeter (MV/cm), enabling breakdown voltages exceeding 1 kilovolt (kV) in compact devices. For context, Si devices top out around 650 volts, while SiC and GaN handle 1.2-1.7 kV but require expensive substrates.

In power electronics, where efficiency means less heat loss and smaller cooling systems, Ga₂O₃ shines. It uses abundant raw materials—gallium from bauxite refining and oxygen—slashing costs. Applications span EV inverters (reducing battery drain by 10-20%), solar inverters (boosting grid integration), and spacecraft power management (radiation-hardened, high-reliability). Japan's push aligns with its Green Growth Strategy, targeting carbon neutrality by 2050.

Nagoya University's Center for Low-temperature Plasma Sciences (cLPS): A Hub of Innovation

Established to pioneer plasma-based technologies, cLPS at Nagoya University integrates plasma science with materials engineering. Professor Hori's team leverages low-temperature plasmas for precise etching, deposition, and radical generation—key to semiconductor fabrication. Prior successes include ammonia-free GaN production and high-speed etching validated with KIOXIA. This ecosystem fosters spinouts like NU-Rei, commercializing plasma tools for Ga₂O₃ growth.

Nagoya's track record in wide-bandgap semiconductors dates back years, with breakthroughs in pn diodes last September 2025. Those diodes doubled current capacity over prior Ga₂O₃ devices and outperformed Si in energy efficiency, published in the Journal of Applied Physics (DOI: 10.1063/5.0282789).

The Six Key Advances: Revolutionizing Ga₂O₃ Processing

The Nagoya team presented a comprehensive process stack at JSAP 2026, spanning epitaxy, doping, and integration. Here's a breakdown:

• 1. High-Density Oxygen Radical Source (HD-ORS): A novel plasma source using ozone-oxygen mix doubles atomic oxygen density, accelerating gallium suboxide conversion to Ga₂O₃ while curbing byproducts. Compatible with MBE and PVD, it sets the stage for scalable growth.
• 2. High-Speed MBE Homoepitaxy: On Sn-doped Ga₂O₃ substrates, achieves 1 µm/hour at just 300°C—low temp minimizes stress. Verified by XRD and RHEED for (001) orientation.
• 3. High-Speed PVD Homoepitaxy: HD-ORS enables >1 µm/hour rates, up to 10x faster than standard MBE, ideal for mass production.
• 4. Silicon Pretreatment: Wet cleaning plus monolayer Ga adsorption prevents Si re-oxidation, priming for heteroepitaxy.
• 5. World-First Ga₂O₃ on Silicon: Heteroepitaxial single-crystal films on 2-inch Si(100) wafers. Si's low cost (10x cheaper) and high thermal conductivity solve Ga₂O₃'s heat issues.
• 6. NiO p-Type Doping: Ni implantation + annealing forms graded NiO layers, yielding pn junctions with 2x current density vs Ni Schottky diodes on Ga₂O₃/GaN.

These integrate seamlessly, paving the way for full devices.

Ga₂O₃ vs Competitors: A Performance Edge

Ga₂O₃ excels in >1 kV apps: Baliga figure-of-merit 4x SiC, 10x Si. SiC/GaN dominate 600-1700V but falter at higher voltages due to substrate costs (~$1000/cm² vs Ga₂O₃ melt-growth $10/cm²). Efficiency: Ga₂O₃ SBDs show Ron*area 30% lower than SiC. Thermal conductivity lags (27 W/mK vs SiC 490), but Si integration mitigates this. Market forecasts predict Ga₂O₃ power devices hitting $200M by 2035, CAGR 43%.

Real-World Impact: EVs, Renewables, and Beyond

In EVs, Ga₂O₃ inverters could extend range 10% via lower losses. Japan's Toyota and Nissan eye it for 2030 models. Renewables: Efficient converters stabilize grids from solar/wind intermittency. Space: Radiation tolerance suits satellites; NASA notes high-voltage PMAD potential. For more on Nagoya's press release, see here.

Japan's Ga₂O₃ Ecosystem: Universities Driving Industry

Nagoya leads, but Tohoku University (FOX Corp spinout for mass production), UMET, and Novel Crystal Technology push boundaries. Government backs via NEDO funding. Unis train talent: Nagoya's semiconductor programs attract global PhDs.

From Lab to Market: NU-Rei's Role

NU-Rei commercializes HD-ORS and p-type tech, partnering fabs. Builds on 2025 pn diodes, targeting prototypes by 2027.

Challenges Ahead and Bright Future

Hurdles: p-type stability, large wafers. Solutions via plasma innovations. Outlook: Ga₂O₃ in EVs by 2030, market $1B+. Nagoya's work accelerates this.

Careers in Japan's Semiconductor Research

Nagoya seeks plasma engineers, epitaxy experts. Thriving field with /research-jobs openings.

Photo by Nemanja Milenkovic on Unsplash