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Novel Crystal Technology (NCT), a global leader in Gallium Oxide (Ga2O3) technology, has successfully grown the first 6-inch Ga2O3 single crystal using the advanced Vertical Bridgman (VB) technique. This achievement marks a significant step forward in NCT’s efforts to deliver larger, high-quality semiconductor wafers for Ga2O3-based power devices.
The VB technique offers several advantages over NCT’s existing Edge-defined Film-fed Growth (EFG) method. By growing the crystal in a cylindrical shape, VB significantly reduces costs associated with substrate cutting. Additionally, it allows for production of substrates in various crystalline orientations, unrestricted by limitations imposed by crystal anisotropy.
Furthermore, the controlled thermal environment of VB growth leads to superior crystal quality with minimal defects, compared to EFG. Finally, dopant uniformity within the substrate is expected to improve, aligning with industry standards for other semiconductors like silicon.
NCT carried out a comparative evaluation between VB and EFG crystals with National Institute of Advanced Industrial Science and Technology (AIST) revealed a dramatic improvement in crystal quality. Synchrotron radiation X-ray topography analysis confirmed minimal defects in the VB-grown crystal, compared to the high density of defects observed in the EFG-grown crystal. This clearly demonstrates the superiority of the VB technique for producing high-quality Ga2O3 substrates.
Ga2O3 is a promising material for power electronics due to its ability to significantly reduce power loss compared to commonly used Silicon Carbide (SiC) in high-voltage applications, like electric vehicles and renewable energy systems. Its wide bandgap characteristics hold immense potential for energy conservation and CO2 emission reduction.
Established in 2015, NCT manufactures 2-inch and 100 mm gallium oxide (Ga2O3) substrates and epi-wafers for power devices. These are commercially available and used by universities, institutes, and power device companies worldwide. NCT currently supplies thousands of these substrates annually to support research and development efforts.
NCT is actively developing larger substrates such as 6-inch. Beyond substrates, NCT has a vision for broader Ga2O3 device production. They are already offering samples of their first Ga2O3 Schottky Barrier Diode, with qualification tests expected to be completed in September 2024.
The development of the Vertical Bridgman growth technique for Ga2O3 single crystals was initiated by Shinshu University, successfully achieving growth of 2-inch and 4-inch crystals. NCT acquired and extended their techniques to enable larger diameter crystal development. This research and development program was partially funded by the Adaptable and Seamless Technology Transfer Program through Target Driven R&D (A-STEP) of the Japan Science and Technology Agency (JST).
Original – Novel Crystal Technology
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The National Science Foundation has given a $300,000 grant to Xiaoqing Song, an assistant professor in the Electrical Engineering and Computer Science Department, to support his research project focused on advancing high density and high-operation-temperature traction inverters. Song’s project explores the integration of gallium oxide packaged power modules to enhance the power density and temperature range of electric vehicles.
Collaborating with the National Renewable Energy Laboratory, the project sets out to innovate power module packaging, establish reliable strategies for gallium oxide power devices and demonstrate the capabilities of a high density, high temperature traction inverter.
“By eliminating technical barriers for gallium oxide device integration, this project will foster the development of next-generation, high density and high-operation-temperature power converters,” Song said.
The traction inverter, responsible for converting stored direct current (DC) power into alternating current (AC) power to drive electric motors, stands to benefit significantly from gallium oxide technology. Song said, “Gallium oxide can make the traction inverter smaller, lighter, more efficient and capable of operating across a wider range of temperatures.
“Gallium oxide has a larger band gap energy compared to conventional silicon and wide band gap semiconductors. It enables high breakdown electrical strength, low intrinsic carrier concentration and correspondingly high operation temperatures,” Song said.
One challenge addressed in the project is the low thermal conductivity of gallium oxide, which hinders efficient heat removal. Song outlines the plan to develop advanced power module packaging techniques that enable low thermal resistance, low parasitic inductances and high-temperature operation capability.
“National Renewable Energy Laboratory (NREL) has significant experience in power module simulation, fabrication and characterization, as well as world-class experimental and lab capabilities for evaluating and designing efficient and reliable power electronics systems. The PI will collaborate with them to design and develop a gallium oxide-based high density and operation-temperature traction inverter for automotive applications. This project will help establish a long-term partnership with NREL that can catalyze further research and development of ultra-wide bandgap power semiconductor devices,” Song said.
Song shared that the collaboration with the National Renewable Energy Laboratory aims to design and develop a gallium oxide-based high density and high-operation-temperature traction inverter for automotive applications, fostering a long-term partnership that can drive further research in ultra-wide bandgap power semiconductor devices.
“Other applications include power grids, data centers, renewable energy, space and defense, etc.,” Song added.
The success of the project, he believes, will provide valuable insights into gallium oxide device modeling, packaging, gate driving, protection and application in power converters. These advancements are expected to catalyze progress in transport electrification and the deployment of gallium oxide technology in challenging environments.
“The research achievements and experiences gained in the fellowship will sustain and promote the PI’s future multi-disciplinary research activities in semiconductor devices, multiphysics analysis, power module packaging and high performance power electronics. Other broader impacts also include the education and development of the next generation workforce in STEM (science, technology, engineering and math), the encouragement of more women and underrepresented minorities in electrical engineering, especially in the area of wide and ultra-wide bandgap semiconductor devices, power module packaging and power electronics with hands-on lab experiences,” Song said.
Original – University of Arkansas
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Mitsubishi Electric Corporation announced that it has taken an equity position in Novel Crystal Technology, Inc., a Japanese company that develops and sells gallium-oxide wafers, a promising candidate for use in superior energy-saving power semiconductors that Mitsubishi Electric intends to develop at an accelerated pace in support of global decarbonization.
Novel Crystal Technology, one of the world’s first companies to develop, manufacture and sell gallium-oxide wafers for power semiconductors, and now a leading producer of these products, has manufacturing technology that Mitsubishi Electric will use in its production of gallium-oxide power semiconductors.
Mitsubishi Electric has been contributing to energy savings in power-electronic products by producing semiconductors made of silicon and silicon carbide (SiC). Recent advances have been achieved with SiC and gallium-nitride wafers, but gallium-oxide wafers are expected to help achieve even higher breakdown voltages and lower power dissipation.
Mitsubishi Electric now expects to accelerate its development of superior energy-saving gallium-oxide power semiconductors by combining its own expertise in the design and manufacture of low-energy-loss, highreliability power semiconductors with Novel Crystal Technology’s expertise in the production of gallium-oxide wafers.
Original – Mitsubishi Electric
