Emerging Powerhouse: Gallium Oxide’s Potential to Revolutionize High-Power Semiconductor Applications

Mitsubishi Electric Corporation announced on July 30 that it has acquired a stake in Novel Crystal Technology, Inc. (referred to as “NCT” below), a Japanese company that develops and sells gallium oxide wafers.

Wide-bandgap semiconductor materials, represented by silicon carbide (SiC) and gallium nitride (GaN), have gained significant popularity in recent years due to their high-temperature resistance, high voltage capability, fast switching speed, high efficiency, energy-saving properties, and long lifespan. However, while the development of wide-bandgap semiconductor materials continues to flourish, the academic and research communities are looking forward to the next-generation semiconductor material – gallium oxide (Ga₂O₃), which is considered a representative of the new generation of semiconductors to replace silicon carbide and gallium nitride.

Mitsubishi Electric has already been involved in the silicon carbide field for many years and has achieved significant results in areas such as air conditioning, high-speed rail, and automotive applications, with its production capacity continuously expanding. As gallium oxide materials and application technologies gradually transition from the research and development stage to commercial applications, the industry believes that gallium oxide is likely to become a dominant player in high-power and high-voltage applications. Based on this, Mitsubishi Electric has made a formal move to enter the gallium oxide market.

Mitsubishi Electric stated that it aims to accelerate the development of energy-saving gallium oxide power semiconductors by combining its expertise in designing and manufacturing high-efficiency power semiconductors with NCT’s expertise in gallium production.

Explaining the advantages of gallium oxide, as a representative of the fourth-generation materials, it possesses several performance advantages, including a large bandgap (4.8 eV), high critical breakdown field strength (8 MV/cm), excellent conductivity (nearly ten times that of silicon carbide), and low material growth cost. The industry believes that in the future, gallium oxide could become a dominant player in high-power and high-voltage applications.

From various public data, it can be observed that gallium oxide outperforms silicon carbide and gallium nitride in various performance indicators. The last two data points, BFOM (measuring high-power performance) and JFOM (measuring radiofrequency performance), both indicate that gallium oxide far exceeds silicon carbide and gallium nitride. Therefore, gallium oxide is inherently suitable for high-power and high-frequency applications, effectively reducing energy consumption in areas such as new energy vehicles, rail transportation, and renewable energy generation.

Currently, five polymorphs of gallium oxide have been discovered, each with unique properties. The most extensively researched is the β-phase (with optimal thermal stability and a bandgap of approximately 4.8 eV), but research on the α-phase (with a high bandgap of ~5.3 eV) and ε-phase (with a polarization ten times that of gallium nitride, suitable for high electron mobility transistors) is also increasing.

Considering the material attributes, gallium oxide holds great promise as an ultra-wide bandgap material. Its advantages not only lie in its high material performance but also in its relatively low cost. In 2019, research findings suggested that gallium oxide’s manufacturing cost is slightly higher than that of silicon but only about one-third that of silicon carbide. However, achieving this cost advantage with current technology remains challenging.

Currently, gallium oxide materials and application technologies are in a critical stage of transitioning from research achievements to commercial applications. However, there are still several technical challenges to overcome, such as difficulties in preparing large-sized gallium oxide single crystals due to their high melting point, high-temperature decomposition, and susceptibility to cracking, as well as incomplete upstream and downstream market-related supporting facilities. At present, all parties in the industry are striving to overcome these obstacles and achieve a leading breakthrough.

The future prospects of gallium oxide are promising, and several players are making moves to capitalize on this potential.

According to industry data, the gallium oxide market is currently dominated by two Japanese companies: NCT and Flosfia. NCT has earned a reputation in the industry since its establishment in 2012 through a joint effort between the National Institute of Information and Communications Technology (NICT) and Tamura Corporation. NICT published the first single crystal β-gallium oxide transistor with a breakdown voltage exceeding 250V. In the same year, NCT achieved a breakthrough in 2-inch gallium oxide crystals and epitaxy technology and later achieved mass production of gallium oxide materials in 2014. In 2017, in collaboration with Tamura Corporation, they successfully developed the world’s first gallium oxide MOS-type power transistor, significantly reducing power consumption to only one-thousandth of traditional MOSFETs. In 2019, they developed 2-inch β-gallium oxide wafers, but due to high manufacturing costs, they were only used in laboratory research and development. However, in 2021, NCT successfully mass-produced 4-inch gallium oxide wafers and began supplying them to customers, establishing Japan’s leading position in the third-generation compound semiconductor race.

It is worth noting that Tamura Corporation achieved mass production of 4-inch gallium oxide in 2019 and also achieved a breakthrough in 6-inch gallium oxide material technology in the same year. The current industry progress involves 6-inch GaN-on-SiC substrates, 6-inch HVPE epitaxy, and 4-inch wafers. According to industry sources, NCT plans to supply 6-inch wafers by 2023.

Flosfia, on the other hand, was incubated by Kyoto University in Japan, with shareholders including Mitsubishi Heavy Industries, Denso (a Toyota subsidiary), and the Japan Bank for International Cooperation. In 2017, the company achieved a breakthrough in low-cost α-gallium oxide material, followed by mass production of α-gallium oxide epitaxial material in 2018. It is rumored that they plan to mass-produce 600V 10A SBDs in 2022 and supply 100,000 devices to Toyota’s new energy vehicles in 2023.