Conventional silicon semiconductors fail above 150°C. But the silicon carbide (SiC) semiconductors under development at Hiroshima University operate at 500°C and withstand mega-gray level radiation. If commercialized, the technology could reshape both long-duration Venus surface exploration and the decommissioning of the Fukushima Daiichi nuclear plant. Here is how a Japanese team achieved the world’s first prototype run in a commercial fab.

The "Extreme Environment" Problem: Why Conventional Semiconductors Fall Short

Semiconductors form the heart of every electronic device in our modern world, from smartphones to automobiles to medical equipment. Yet conventional silicon semiconductors have a critical weakness: they malfunction above approximately 150°C due to thermal runaway. Under radiation, they fail at around 0.2 kGy (kilogray).

What does this mean in practice? In outer space, inside nuclear facilities, deep underground drilling sites, or within jet engines, these "extreme environments" require elaborate cooling systems or radiation shielding for electronics to function. Sometimes, electronic devices simply cannot be used at all.

A research team led by Professor Shinichiro Kuroki at Hiroshima University's Research Institute for Semiconductor Industrial Technology is working to break through these limitations by developing integrated circuits using Silicon Carbide (SiC).

The Remarkable Properties of Silicon Carbide

Silicon Carbide is a compound of silicon and carbon. It possesses hardness second only to diamond, excellent thermal conductivity, and extreme chemical stability.

SiC's greatest advantage as a semiconductor lies in its wide bandgap. While silicon has a bandgap of approximately 1.1 eV (electron volts), SiC (4H-SiC type) has about 3.3 eV, nearly three times larger. This means thermal excitation of electrons is suppressed even at high temperatures, enabling stable operation at 500°C.

Radiation tolerance is also orders of magnitude better. While conventional silicon semiconductors degrade at a few kGy, SiC integrated circuits have been confirmed to withstand MGy (megagray) levels, over 1,000 times more radiation.

World's First: Successful Prototype Production in a Commercial Fab

In April 2025, a joint team from Hiroshima University and Phenitec Semiconductor Corporation (Ibara City, Okayama Prefecture) achieved the world's first successful prototype production of SiC integrated circuits in a commercial semiconductor fabrication facility.

Using the 6-inch wafer line at Phenitec's Kagoshima factory (Yusui Town, Kagoshima Prefecture), the team spent approximately one year establishing circuit design and manufacturing processes. The resulting prototype wafers include CMOS image sensor test chips and process evaluation devices.

Previously, SiC integrated circuit fabrication was only possible in Hiroshima University's super clean room research facility. Success in a commercial fab represents a major step from research to practical implementation. Technology transfer toward establishing a SiC integrated circuit foundry is now becoming a realistic prospect.

Application 1: Venus Exploration

One of the most dramatic applications for SiC semiconductor technology is Venus surface exploration.

Venus is sometimes called "Earth's twin," but its surface environment is hellish. Atmospheric pressure is about 93 times Earth's (9.4 MPa), and the thick CO₂ atmosphere creates a greenhouse effect maintaining surface temperatures around 460°C day and night. Sulfuric acid clouds swirl in the upper atmosphere.

In 1982, the Soviet Venera 13 lander successfully touched down on Venus and transmitted color photographs to Earth. However, despite electronic equipment protected by pressurized vessels with lithium salt cooling systems, it ceased functioning after just 127 minutes, still the longest operational record for any Venus surface mission.

NASA Glenn Research Center developed SiC JFET (Junction Field-Effect Transistor) integrated circuits and tested them in the Glenn Extreme Environments Rig (GEER), which replicates Venus surface conditions. The results: over 60 days of continuous operation without cooling or shielding, representing more than 100 times the durability improvement over conventional systems.

NASA is developing the LLISSE (Long-Life In-situ Solar System Explorer) project, a Venus lander equipped with SiC electronics. While previous landers required approximately 700 kg of mass, LLISSE could be designed under 20 kg by eliminating environmental protection systems.

Hiroshima University's technology aligns with this space exploration trend. Professor Kuroki's laboratory is conducting research under the KAKENHI Grant-in-Aid project titled "Establishment of SiC Extreme Environment Electronics to Support Expansion of Human Frontier," explicitly targeting space applications.

Application 2: Fukushima Daiichi Nuclear Decommissioning

Another critical application is decommissioning work at the Fukushima Daiichi Nuclear Power Station.

More than 14 years after the 2011 accident, retrieval of melted nuclear fuel (fuel debris) remains the greatest challenge. The interior of the reactor containment vessels experiences ultra-high radiation levels reaching hundreds of sieverts per hour (a 2017 survey recorded up to 650 Sv/h), environments where not only humans but ordinary electronic equipment loses functionality within hours.

Survey robots deployed so far (PMORPH, Mini-Manbo, Spot, etc.) incorporate radiation-hardened designs, but camera and sensor lifespans remain bottlenecks for decommissioning work. During a 2017 Unit 2 investigation, the robot's onboard camera darkened after accumulating 1,000 Sv of radiation, forcing retreat after approximately two hours.

If SiC-based image sensors and control circuits are commercialized, this situation would fundamentally change. Hiroshima University is advancing R&D on "MGy-class radiation-resistant image sensors" through a commissioned project from the Fukushima International Research for Nuclear Decommissioning (F-REI). MGy-class means radiation tolerance over 1,000 times current equipment.

Enabling long-duration, high-precision internal surveys would allow accurate mapping of fuel debris distribution, efficient removal planning, and reduced worker exposure. The 30-40 year timeline projected for decommissioning completion could potentially be significantly shortened.

From EVs to Healthcare: Expanding Applications

Technology for extreme environments also yields spillover benefits for everyday life.

Electric vehicle (EV) motor surroundings reach high temperatures during operation. Currently, SiC power semiconductors are used in many EVs including Tesla's Model 3, but control circuits remain silicon-based and require cooling systems. If SiC integrated circuits are commercialized, cooling-free control systems become possible, leading to lighter, more efficient EVs.

Other applications include monitoring inside jet engines, deep-sea drilling, geothermal power plant control systems, "places where electronics couldn't be used" before. Medical applications such as radiation therapy equipment are also being explored.

Challenges and Outlook

Several challenges remain before SiC semiconductor technology reaches full commercialization.

First, integration density. Current SiC integrated circuits are at the scale of hundreds of transistors, equivalent to 1970s silicon integrated circuits. Considering modern smartphone processors contain tens of billions of transistors, the gap is stark. However, extreme environment applications don't necessarily require high integration density, so commercialization is expected to proceed first for specific applications.

Second, manufacturing costs. SiC wafers are more expensive than silicon wafers, and processes are still being established. Development of commercial foundries is expected to drive cost reduction.

Third, reliability demonstration. Space and nuclear equipment require extremely high reliability. Long-term testing in actual environments and data accumulation are necessary.

Professor Kuroki offers his outlook: "SiC semiconductor LSIs will likely be commercialized first in fields where silicon semiconductors are impossible, such as space probes and nuclear power plants. After that, applications will gradually expand to EVs and other areas."

Japanese Technology Expanding Humanity's Frontier

"Supporting the expansion of human frontier", these words embedded in Hiroshima University's research project title are not mere rhetoric.

Exploration probes operating for months on Venus's surface. Robots capable of long-duration surveys in Fukushima Daiichi's deepest areas. Intelligent systems performing self-diagnosis inside scorching jet engines. Sensors conducting long-term observations at 10,000 meters underwater.

All of these become possible for the first time through SiC semiconductor technology. And at the forefront of this technology stands a Japanese research team.

The world's first commercial fab prototype success marks the first step in technology transfer from laboratory to factory to society. With the "Setouchi Semiconductor Co-Creation Consortium" centered on Hiroshima University now in full operation, this effort may also play a role in revitalizing Japan's semiconductor industry.

SiC semiconductors challenging extreme environments. This endeavor will surely expand the places humanity can go and the worlds we can know.

In Japan, expectations are rising for this technology to contribute to Fukushima decommissioning and future space exploration. What research or interest exists in your country regarding semiconductors usable in extreme environments? What are your views on technological innovation in space exploration and the nuclear sector? We'd love to hear your perspective!

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