Back in 2011, the world held its breath after the Fukushima Daiichi nuclear plant in Japan suffered a failure of its cooling systems, in the wake of the country getting hit by a 9.0 magnitude earthquake and tsunami. The worry was not unfounded: the resulting meltdown — which spread highly radioactive material in multiple directions — became one of the worst nuclear-related disasters of all time.

More than a decade on, the clean-up is still in progress. Last month, the Japanese government began a testing procedure to remove radioactive debris in and around the plant — a significant step in the plant’s decommissioning process, expected to be completed by 2051.

A groundbreaking startup from Japan, Ookuma Diamond Device (ODD), is playing a fascinating part in the process, by way of diamond chips that are being used in efforts to remove radioactive debris, by way of diamond-chip-powered amplifiers. And now, it has raised 4 billion yen, equivalent to approximately $27 million, to build the world’s first diamond semiconductor manufacturing facility in nearby Ookuma, also in Fukushima.

ODD’s plans are to build the factory in January 2025 and have it up and running by Summer 2026.

Why use diamond chips rather than traditional silicon-based semiconductors?

Diamond is known as a wide-bandgap (WBG) semiconductor material — others include SiC (silicon carbide) and GaN (gallium nitride). WBG materials are considered to have better power conversion efficiency and exceptional thermal management.

Unlike silicon-based CPUs, GPUs, and NPUs, but the diamond-based chip do not have a circuit structure. Diamond semiconductors act more like powerful control devices than small electricity sources, Cocal Capital partner Ken Nishimura told TechCrunch. He said that the diamond semiconductor will be used in larger facilities such as nuclear power plants that require super high temperatures and radiation levels, which silicon-based chips cannot withstand.

Diamond semiconductor amplifiers operating under 300°C have been successfully prototyped using the National Institute of Advanced Industrial Science and Technology (AIST) and Hokkaido University facilities.

“Diamond semiconductors, which we develop, are fundamentally different from traditional silicon-based chips due to their superior material properties,” Yuhei Nagai, CFO of Ookuma Diamond Device, said in an exclusive interview with TechCrunch. Compared to other advanced semiconductors like SiC and GaN, diamond semiconductors provide superior power conversion efficiency and improved thermal management for next-generation technologies such as 6G, space, defense, and nuclear, he continued.

It’s also notable that diamond chips can be made from methane gas, potentially enabling full production in Japan. This is in contrast to GaN, which relies sourcing materials heavily controlled by China.

ODD’s focus is on developing “pure diamond semiconductors,” rather than GaN semiconductors on a diamond substrate, Nagai said. The market size for diamond materials used in chips is expected to grow to $10 billion by 2032, up from $113.7 million in 2023., according to a recent report.

The startup, a spinout from Japan’s National Institute of Advanced Industrial Science and Technology (AIST) and Hokkaido University, was specifically founded in 2021 to help with decommissioning the Fukushima Daiichi Nuclear Power Plant.

Two co-founders, Dr. Junichi Kaneko and Dr. Hitoshi Umezawa, have researched diamond chips for over 20 years. They found their work thrown into the spotlight after the disaster, which spelled more resources for R&D and spurred the founding of the startup. ODD built the world’s first practical diamond chip in 2021.

The leaps between theory, chip, and final product are still significant. The two co-founders are also leading the Japanese government’s wider national project to make an actual product that could remove radioactive debris from natural disasters. 

“The [ODD’s] prototypes represent a world-first achievement—no one else has been able to develop functioning diamond semiconductor amplifiers to this point,” said Nagai.

A handful of global companies are also developing diamond semiconductors, including Diamfab in France, Element Six in the U.K., and A.L.M.T. in Japan, a subsidiary of Sumitomo Electric Industries.

ODD sets itself apart by claiming to be the only one with end-to-end expertise, from substrate to packaging, enabling the world’s prototype of a diamond semiconductor amplifier.

ODD is also talking with more than 10 potential customers worldwide in the nuclear power plant, aerospace, and telco industries, Nagai said — an area that this week got increased focus after it emerged that Google signed a deal to work on powering data centers with nuclear power.

Globis Capital partners led the recent funding, which brings its total raised to approximately $45 million (6.7 billion yen) since its inception, with participation from Coral Capital, aSTART, Green Co-Invest Investment, Japan Post Bank Spiral Regional Innovation Fund, Mitsui Sumitomo Insurance venture capital, SMBC Venture Capital, among others.

The startup, which currently has 27 employees, has also received around $15 million in government grants from the Cabinet Office, METI, MIC, ATLA, and the Reconstruction Agency.