Ultra-wide bandgap surpasses GaN and SiC in power electronics
Key Takeaways
- Ultra-wide bandgap (UWBG) surpasses wide bandgap but scaling up is a challenge
- Thermal conductivity is problematic
- Breakthroughs are coming from academia
Gallium oxide (Ga₂O₃) is emerging as a leading ultra-wide bandgap (UWBG) semiconductor material with the potential to deliver higher efficiency, superior voltage tolerance and cost advantages compared to gallium nitride (GaN) and silicon carbide (SiC). This article explores Ga₂O₃’s technical strengths, recent university research breakthroughs at Bristol (UK). Swansea (UK) and Nagoya (Japan), and its expanding role in energy and power electronics. Remaining challenges and diverse application prospects highlight both the promise and the path ahead for this transformative material.
Why gallium oxide matters now
The shift toward ultra-wide bandgap semiconductors is reshaping power electronics, driven by demands for higher voltages, greater switching frequencies and improved energy efficiency from automotive to grid-scale systems. Gallium oxide distinguishes itself among UWBG candidates by possessing a bandgap of approximately 4.8 to 5.0 eV, which is substantially wider than the 3.4 eV of GaN and 3.3 eV of SiC.
This translates into an impressive critical electric field strength of around 8 MV/cm, more than double that of GaN, enabling the development of devices capable of operating at ultra-high voltages with smaller chip sizes and reduced power loss. These characteristics suggest groundbreaking potential for downsizing and optimizing power conversion equipment critical to electric vehicles, renewable energy systems and data centers.
Not only does Ga₂O₃ enable lower conduction losses and hence better efficiency, but its wide bandgap also confers inherent robustness to radiation and temperature effects, an appealing property for aerospace and robust industrial electronics. This combination positions gallium oxide as a pivotal material for next-generation power devices aimed at improving global energy sustainability.
Swansea University (UK) claims breakthrough
Scaling gallium oxide from a niche research material to an industrial semiconductor relies on producing large, high-quality wafers. Swansea University in the UK has established the country’s first facility capable of growing 4-inch diameter Ga₂O₃ thin films using metal-organic chemical vapor deposition (MOCVD).
Manufacturing gallium-oxide wafers
Swansea University’s close-coupled showerhead at its Oxide and Chalcogenide Metalorganic Chemical Vapor Deposition (MOCVD) reactor shows a 4-inch gallium oxide thin film on sapphire being unloaded. (Source: Dr. Dan Lamb, Swansea University)
The university’s Centre for Integrated Semiconductor Materials’ state-of-the-art facility houses a new Oxide and Chalcogenide Metalorganic Chemical Vapor Deposition (MOCVD) Laboratory, which is set to become a national hub for thin-film gallium oxide research and development and forms the backbone of the UK's budding UWBG semiconductor supply chain, reinforced by collaborations with major industry partners such as IQE and Microchip.
The research hub benefits from national funding and integrates within Europe’s growing UWBG eco-system, helping position the UK for a competitive role in global power semiconductor technology while supporting applications spanning electric vehicles to 5G communications.
Bristol (UK) center makes progress on deposition processes
The University of Bristol has a dedicated Ga₂O₃ epitaxial reactor with which it has successfully deposited advanced films on diamond and sapphire substrates, as well as bulk Ga₂O₃ wafers. Hetroepitaxy, the process of growing a crystalline layer of one material onto a crystalline substrate of a different material, will be important for the scaling up and economic commercialization of Ga₂O₃ devices.
The researchers have been fabricating trench Schottky barrier diodes (TSBDs) with a conformal coating of a dielectric material, Al₂O₃. For a given device architecture, the breakdown voltage of the devices is primarily limited by the breakdown strength of the dielectric layer.
The Bristol team has been working with Oxford Instruments Plasma Technology (OIPT) to replace dielectric deposited using thermal atomic layer deposition (ALD) with Plasma Enhanced ALD (PEALD). The denser, high-quality, high-breakdown PEALD has increased the breakdown voltage of the Schottky barrier diodes to 4 kV, the highest for a Ga₂O₃ device currently reported by research teams. A high breakdown voltage is desirable because it Improves device robustness, making it less likely to fail due to voltage spikes or electrical overstress. Experiments are continuing to further increase the figure. PEALD also offers opportunities to improve the quality of the interface between the dielectric and the Ga₂O₃ surface to reduce leakage current and variability in device performance.
Transistor profile and transfer characteristics for gallium oxide
How gallium oxide trench Schottky diodes have been fabricated with plasma enhanced atomic layer deposition of the Al₂O₃ dielectric layer to boost their breakdown voltage from 1.5 kV to 4 kV. (Source: Bristol University, UK)
“The advances in dielectric deposition using PEALD at Bristol are genuinely world leading. Achieving 4 kV breakdown voltages in Ga₂O₃ trench Schottky barrier diodes shows what’s possible when we combine deep materials understanding with precision process control,” said Dr. Katie Hore, Innovation Director, REWIRE, University of Bristol. “This kind of progress paves the way for Ga₂O₃ devices to outperform silicon carbide in the most demanding high-voltage applications.”
Another important aspect of the research at Bristol is to reduce wafer defects. After many decades of development, the defects in SiC wafers have been reduced to below 100 defects/cm2. In Ga₂O₃ they are still in the range 10,000-100,000 defects/cm2 and their effects on device performance are poorly understood. This is a major challenge for scaling the production of Ga₂O₃ devices. The research team is working on identifying different types of defects, fabricating devices on known defect sites to analyze their effect on the final devices and to determine whether they are the driver for device failure.
Nagoya University solves gallium oxide p-type conduction challenge
A long-standing obstacle to gallium oxide’s practical impact was the difficulty of creating stable p-type layers, a prerequisite for forming pn junctions, essential components of diodes and transistors. Nagoya University’s breakthrough provides a scalable industrial method to overcome this critical limitation.
By implanting nickel ions into Ga₂O₃ substrates and employing a dual-phase annealing process, initial oxygen plasma treatment followed by a high-temperature oxygen furnace anneal, the nickel converts into nickel oxide, generating reliable p-type conduction within the gallium oxide film.
This innovation has resulted in high-performance PN diodes that can handle twice the current capacity of previous Ga₂O₃ devices while significantly reducing energy losses. Commercialization efforts by spin-off company NU-Rei aim at power switching devices for electric vehicles, renewable energy converters, and high-efficiency rectification, promising significant efficiency gains and cost savings in energy-intensive sectors.
This solves a fundamental roadblock and paves the way for a full suite of Ga₂O₃-based power devices on par with or better than current GaN or SiC technologies.
Diverse applications driving gallium oxide adoption
Gallium oxide’s unique performance and production advantages open a wide spectrum of applications.
- In electric vehicles, Ga₂O₃-based devices can improve traction inverters, onboard chargers and DC-DC converters, delivering higher efficiencies and reducing cooling demands compared to silicon-based and conventional WBG devices.
- Renewable energy systems such as solar inverters, wind turbine converters and smart grid interface equipment benefit from high-voltage, low-loss switching capabilities.
- Industrial motor drives also leverage gallium oxide’s wide bandgap to reduce size and enhance robustness.
- In high-frequency RF and power amplification, Ga₂O₃’s superior bandgap can enable lower parasitic losses, crucial for emerging high-speed telecommunications and radar infrastructure.
- Emerging space exploration missions utilize Ga₂O₃’s radiation hardness and thermal tolerance for compact power distribution units, evidenced by NASA-funded Ga₂O₃ power electronics development for future spacecraft.
Together, these applications will drive demand for Ga₂O₃ materials, devices and integrated modules, supporting an expected compound annual growth rate (CAGR) exceeding 40 percent through the 2030s.
How gallium oxide stacks up against GaN and SiC
| Parameter | Gallium oxide (Ga₂O₃) | GaN | SiC |
|---|---|---|---|
| Bandgap (eV) | 4.8–5.0 | 3.4 | 3.3 |
| Critical electric field | ~8 MV/cm | ~3 MV/cm | ~2 MV/cm |
| Electron mobility | Moderate to low | High | Moderate |
| Thermal conductivity | Low (0.1–0.3 W/cm·K) | High (1.3–2.5 W/cm·K) | High (4.9 W/cm·K) |
| Device maturity | Early-stage, emerging | Mature, commercial | Mature, commercial |
| Voltage handling | Very high, superior | High | High |
Gallium oxide promises substantially improved bandgap, breakdown field, and voltage handling characteristics for power semiconductors but thermal management is more challenging due to the material’s low thermal conductivity.
Primary challenges, thermal management and device reliability
Ga₂O₃ faces several ongoing hurdles before it can challenge GaN and SiC at scale.
- Despite the ability to operate at high junction temperatures, its intrinsically poor thermal conductivity complicates heat dissipation, which increases cooling requirements or demands advanced packaging strategies.
- Gallium oxide’s p-type doping optimization is recent but still at an early stage, further refinement is needed for industrial-scale production of a full device portfolio.
- Long-term reliability under thermal cycling, radiation exposure and high-voltage stress must be comprehensively validated before Ga₂O₃ enters critical industrial or aerospace markets.
- The technology also requires integration with mature device fabrication lines and effective thermal interface materials, such as diamond or graphene composites, to realize its full potential.
Addressing these will be the focus of both academic and corporate research and development in the coming years.
Market outlook
Market forecasts project that gallium oxide power devices will capture a significant share of the growing UWBG semiconductor market, driven by electrification, renewable energy expansion and next-generation communications infrastructure.
Growth is fueled by Ga₂O₃’s combination of high-voltage capability, manufacturability at scale and versatile applications ranging from EV powertrains to grid converters and future aerospace electronics. The synergy of Swansea and Bristol’s scalable production and Nagoya’s device innovations illustrates the path from research to robust commercial products.
As silicon slowly cedes ground and GaN and SiC seek next-generation successors, Ga₂O₃ will likely emerge as a third pillar of UWBG semiconductors, poised to power an era of lower emissions, higher efficiency and smaller system footprints.
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