In a breakthrough development, Novel Crystal Technology, Inc. has achieved an ampere-class 1200-V breakdown-voltage Schottky barrier diode (SBD). The company has been working on the commercial development of β-Ga₂O₃ Schottky barrier diodes as part of Japan’s New Energy and Industrial Technology Development Organization (NEDO) Strategic Energy Conservation Technology Innovation Program.

The new epoch-making development will greatly advance the commercialization of gallium oxide SBDs with high breakdown voltages. This will lead to cheaper but higher-performance power electronics.

Also, the new product will enable more efficient and miniaturized power electronics devices, like power converters for photovoltaic power generation, general-purpose inverters for industrial use, and power supplies. Thus, this SBD can contribute to the efficient use of electric energy, for example, electrification of automobiles and flying cars.

Development of Gallium Oxide

Gallium oxide (β-Ga₂O₃) has superior material properties and has cheaper crystal growth method than that of silicon carbide (SiC) or gallium nitride. These are competing high-performance materials to replace silicon. Low-loss, low-cost power devices can be made from β-Ga₂O₃. Its use is expected in home appliances, electric vehicles, railway vehicles, industrial equipment, solar power generators, and wind power generators. Companies and research institutes are accelerating the research and development on β-Ga₂O₃ with the goal of using this material to miniaturize and improve the efficiency of electrical equipment.

Development History

In 2017, Novel Crystal Technology embarked on commercializing β-Ga₂O₃ devices. Since then, it has been working on demonstrating β-Ga₂O₃ SBDs as part of the Strategic Energy Conservation Technology Innovation Program of NEDO. The company has developed a mass-production process for trench-type β-Ga₂O₃ SBDs on 2-inch wafers using its research prototype line and a foundry. It has also developed the first ampere-class 1200-V breakdown-voltage β-Ga₂O₃. It is expected that high-voltage β-Ga₂O₃ SBDs will find use in next-generation quick chargers.

Tamura Corporation, the parent company of Novel Crystal Technology, developed the first β-Ga₂O₃ epitaxial wafers for power devices in 2015. It was made through the same NEDO-funded project under the “Research and development of ultra-high voltage gallium oxide power device” from 2011 to 2013.

Since 2018, the company has been developing practical β-Ga₂O₃ SBDs for power devices in the same project under “Research and development of ampere-grade gallium oxide power device.”

The success reported here is based on the results of another NEDO-funded project “Commercial development of β- Ga₂O₃ SBD.” Novel Crystal Technology has been participating in this project since 2020.

Achievements

Until now, the planer type structure, which is relatively easy to process, has been used for high-current β-Ga₂O₃ SBDs. However, as the planer type has a large leakage current, it is difficult to manufacture a planer Ga₂O₃ SBD with a breakdown voltage of 1200V.

In 2017, Novel Crystal Technology demonstrated a trench-type Ga₂O₃ SBD that reduces reverse leakage current to 1/1000. Since then, it has been improving the device’s breakdown voltage and increasing the current.

Figure 2 shows an optical image and a schematic cross-section of the developed β-Ga₂O₃ field-plated trench MOSSBD. The device has a forward current 10 IF of 2A (VF = 2.0V) (Figure 3a), breakdown voltage of 1200V, and low leakage current <10^-9A (Figure 3b).

At present, the company mass produces SBDs on 2-inch wafers by using a research prototype line and a foundry.

Future Plans

Through its participation in NEDO projects, Novel Crystal Technology will establish the manufacturing process and ensure the reliability of these new 1200-V breakdown-voltage β- Ga₂O₃ SBDs, aiming for commercialization in 2023. The company will also build a 100-mm mass-production foundry line for high-quality β-Ga₂O₃ 100-mm epitaxial wafers, which started to go on sale in June 2021.

The market for medium- and high-voltage high-speed diodes, which is expected to expand to 120 billion yen (US$1.04 billion) in 2022 and 150 billion yen (US$1.29 billion) by 2030 would especially benefit from this development. Novel Crystal Technology will enter this market with its β-Ga₂O₃ SBDs and contribute to energy saving.