On the one hand, the computer chips convert the electrical energy supplied into heat during the computing processes. This heat has to be dissipated via cooling systems, which requires additional energy. Researchers led by Prof. Qing-Tai Zhao from Forschungszentrum Jülich have therefore analyzed how much energy can be saved when computing at very low temperatures. Prof. Joachim Knoch from RWTH Aachen University and other scientists from EPFL in Switzerland, the company TSMC and the National Yang Ming Chiao Tung University (NYCU) in Taiwan as well as the University of Tokyo were involved in the study on cryogenic computing, as reported by Forschungszentrum Jülich. Studies show that savings of up to 70 % are possible at -196.15 °C. This temperature can be achieved with liquid nitrogen cooling. The savings potential still includes the cost of cooling. With helium cooling at -269 °C, it is even 80 %, the researchers write.
Sub-nanometer thin films contribute to the solution
In practice, however, things have been different so far. This is because at very low temperatures, physical phenomena become noticeable that are lost in the "thermal noise" at higher temperatures. These challenges can be overcome. Ultimately, the realization of cryogenic computing requires "the replacement of materials established in commercial CMOS technology with novel materials or the integration of newly evaluated known materials", as Prof. Joachim Knoch from RWTH Aachen University explains. In the study, the researchers suggest how a kind of "super transistor for the cold" could be made possible. These include: Gate-all-around nanowires and fully depleted silicon-on-insulator (SOI) structures that enable particularly precise control, high-k dielectrics with a very high dielectric constant in combination with sub-nanometer thin interlayers that reduce energetic disorder and efficiently concentrate the electric field, source/drain engineering, which enables the formation of steep transitions and causes fewer defects, the use of new types of materials such as semiconductors with a small band gap, which allow switching at lower voltages, and back-gating, which allows the threshold voltage to be dynamically adjusted.
"Cold-optimized chips could help save a lot of energy, especially in high and supercomputing centers where thousands to hundreds of thousands of chips are used," explains Hung-Li Chiang, a scientist at TSMC, the world's largest semiconductor manufacturer based in Taiwan.
Developments can be used for quantum computers
The "cold chips" are also relevant for the electronics of quantum computers. This is because the sensitive quantum states in quantum computers are extremely sensitive. Heat is practically poison for quantum computers, which are usually cooled to temperatures close to absolute zero using special cooling devices - cryostats.
These demanding applications are also the focus of the Jülich research group led by Qing-Tai Zhao. "The requirements for quantum electronics are particularly high. However, related developments could open up new avenues for high-performance computers at cryogenic temperatures and universal cryogenic computers with extremely low power consumption that integrate von Neumann, quantum and neuromorphic processors," explains Zhao.