27 May 2025
Modern computer chips generate a lot of heat - and consume large amounts of energy as a result. A promising approach to reducing this energy demand could lie in the cold, as highlighted by a new perspective article by an international research team coordinated by Qing-Tai Zhao from Forschungszentrum Jülich.
The work was conducted in collaboration with researchers from RWTH Aachen University, EPFL in Switzerland, TSMC and NYCU in Taiwan, and the University of Tokyo. In the article, published in Nature Reviews Electrical Engineering, the authors outline how conventional CMOS technology can be adapted for cryogenic operation using novel materials and intelligent design strategies.
Data centers already consume vast amounts of electricity - and their power requirements are expected to double by 2030 due to the rising energy demands of artificial intelligence, according to the International Energy Agency (IEA). The computer chips that process data around the clock produce large amounts of heat and require considerable energy for cooling. But what if we flipped the script? What if the key to energy efficiency lay not in managing heat, but in embracing the cold?
This is the idea behind the concept of cryogenic computing, i.e., computing at very low temperatures. In the future, computer chips could not only work faster but also more efficiently at these temperatures-at least if they are adapted accordingly. The approach is also interesting for numerous applications such as quantum computers, space probes, and medical imaging, which often require very low temperatures close to absolute zero. Conventional chips can also benefit from powerful cooling. However, they are only suitable for truly cryogenic operation to a limited extent.
Transistors like it cold - actually
"Transistors account for a large proportion of the power consumption in computers," says Qing-Tai Zhao. These tiny switches - modern chips often contain several billion per square millimeter - require a certain voltage to switch between on and off. At room temperature, around 60 millivolts are required to limit the current flow to one tenth. This value, known as the "subthreshold swing," is a measure of a transistor's switching efficiency - and is highly temperature-dependent.
"Traditionally, this switching voltage decreases as the temperature drops. That's because electrons have less thermal energy. They don't 'jump' over barriers as easily and behave more predictably overall. Near absolute zero, theoretically only 1 millivolt would be required," Zhao explains. Less voltage means less energy, less heat, and greater efficiency.
In fact, studies show that at 77 Kelvin (-196.15 °C) - a temperature still achievable using liquid nitrogen cooling - energy savings of up to 70 percent are possible. This remains true even when the energy needed for cooling is factored in. With helium-based cooling at 4 Kelvin, savings could reach as high as 80 percent, according to the researchers.
Theory vs. practice
However, the reality is somewhat different. At very low temperatures, physical phenomena become apparent that are masked by "thermal noise" at higher temperatures. The most notable of these are the so-called band tail effects: energetic disturbances caused by small material disorders or defects, as no semiconductor is perfect. "They prevent transistors from switching off properly," says Zhao. The current continues to "leak" even though the component should actually be blocked.
In addition, there's source-drain tunneling, a quantum phenomenon in which electrons pass directly through the barrier region. Together, these effects prevent the subthreshold swing from decreasing as much as expected. Instead of reaching values below 1 millivolt per decade, the subthreshold swing typically settles between 5 and 10 millivolts per decade at temperatures below 20 Kelvin - far too high to achieve the energy efficiency theoretically possible.
New materials, new perspectives
The good news is that there are solutions. In their study, published in Nature Reviews Electrical Engineering, the researchers propose a whole range of technologies that, in combination, could enable a kind of "super transistor for the cold." These include:
- Gate-all-around nanowires and fully depleted Silicon-On-Insulator (SOI), which enable particularly precise control
- High-k dielectrics, which efficiently bundle the electric field,
- Source/drain engineering, which enables steep junction formation and introduces less defects,
- the use of novel materials such as small band gap semiconductors, which allow switching with lower voltages,
- and so-called back gating, in which the threshold voltage can be dynamically adjusted.
From lab to application
Such cold-optimized chips could significantly reduce energy consumption - especially in high-performance data centers where thousands or even hundreds of thousands of chips are deployed. But they are also especially relevant to quantum computing, where the fragile quantum states used for processing are extremely sensitive to interference. Heat is particularly detrimental, which is why quantum computers are typically operated at temperatures well below 4 Kelvin using specialized cooling systems called cryostats.
These demanding applications are also the focus of Zhao's research group at Forschungszentrum Jülich. "The requirements for quantum electronics are extremely high. But the technologies being developed in this context could pave the way for high-performance computing at cryogenic temperatures, and for universal cryogenic systems that combine von Neumann, quantum, and neuromorphic processors - all with ultra-low power consumption," Zhao explains.
Major semiconductor manufacturers are also working on this topic. Experts from TSMC, the world's largest chip foundry based in Taiwan - known for producing high-performance chips for companies like Apple, Nvidia, and AMD - were also involved in the current study.
Original publication
Zhao, QT., Han, Y., Han, HC. et al.
Ultra-low-power cryogenic complementary metal oxide semiconductor technology
Nat Rev Electr Eng (2025), DOI: 10.1038/s44287-025-00157-7
