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.
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.
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.
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.
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.