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NEDO project confirms operation of gallium‐oxide Schottky barrier diodes: Prospects for application in power electronics devices


On April 6, NEDO (New Energy and Industrial Technology Development Organization) announced that Novel Crystal Technology, which is working on commercial development of β‐Ga2O3 Schottky barrier diodes as part of its Strategic Energy Conservation Technology Innovation Program, confirmed the successful operation of gallium‐oxide (β‐Ga2O3) Schottky barrier diodes (SBDs) for power devices. When the 1200 V breakdown voltage gallium‐oxide SBDs that are currently under development were evaluated in a current‐continuous PFC (power factor correction) circuit, it was confirmed that they operate properly at a high output voltage and power of 390 V and 350 W, respectively. This is the first time that successful operation of an actual device at a high‐power output has been confirmed in Japan. In addition, a comparison of their power conversion efficiency with that of silicon (Si) fast recovery diodes (Si FRDs), which are widely used for power devices, showed a 1% improvement in efficiency, confirming their energy efficiency.

Photograph of developed β‐ Ga2O3 SBDs
Provided by Novel Crystal Technology, Inc.

Silicon carbide (SiC) and gallium nitride (GaN) have been actively studied as new materials with superior performance to silicon (Si) semiconductors. However, gallium oxide demonstrates significantly superior material properties and the added advantage of being able to produce high‐quality single‐crystal substrates at low cost using "the melt growth method."

Owing to these characteristics, the use of gallium‐oxide power devices in practical applications has the potential to further reduce the loss and cost of power electronics systems, such as home appliances, electric vehicles, railway vehicles, industrial equipment, and solar and wind power generation equipment. Therefore, domestic and foreign companies, as well as research institutions, are accelerating their research and development efforts.

Novel Crystal Technology has been working on the development of gallium‐oxide SBDs under NEDO's "Strategic Energy Conservation Technology Innovation Program / Commercial development of β‐Ga2O3 SBD" project from 2020 to 2022. To date, the project has achieved significant results, including the successful development of high‐quality gallium‐oxide 100‐mm epi‐wafers and gallium‐oxide SBDs with a breakdown voltage of 1200 V and an ampere‐class rating.

In this study, they introduced a gallium‐oxide SBD under development in a continuous‐current PFC circuit and evaluated it for practical use. The circuit operation at a high voltage of 390 V and output power of 350 W was successfully demonstrated. The gallium‐oxide SBD developed was tested in a PFC circuit with a high output power (350 W) supply to demonstrate continuous current operation. The ratio of output power to input power of the circuit (power conversion efficiency) was calculated after verifying the operation. It was confirmed that the efficiency of the gallium‐oxide SBD improved by 1% compared to that of a Si FRD.

Novel Crystal Technology plans to establish a manufacturing process for the gallium‐oxide SBD that was successfully developed on a 4‐inch foundry line. The company plans to concurrently develop next‐generation gallium‐oxide SBDs with a trench structure to achieve even higher performance. In addition, research and development of inversion metal‐oxide‐semiconductor (MOS) transistors will also continue while exploiting the results of this development.

NEDO anticipates that the results of this research will pave the way for the development of gallium‐oxide power devices that can be used in various applications, such as power conditioners for photovoltaic power generation, general‐purpose inverters for industrial use, power electronics equipment (such as power supplies) with higher efficiency and smaller sizes, electrification of automobiles, and flying cars, etc. Such devices will improve the efficiency of electric energy.

Starting with the widespread use of gallium‐oxide SBDs in industrial general‐purpose inverters and power supplies, NEDO aims to achieve an energy saving effect of 100,000 kL/year (crude oil equivalent) in Japan over the next 30 years through reduced power consumption by expanding the use of these diodes to various power electronics devices.

This article has been translated by JST with permission from The Science News Ltd. ( Unauthorized reproduction of the article and photographs is prohibited.

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