Researchers at The Hong Kong Polytechnic University (PolyU) have engineered a novel tunnelling field-effect transistor (TFET) that overcomes the physical 'Boltzmann limit,' a barrier that has constrained the energy efficiency of traditional transistors for decades. The breakthrough, published in the prestigious journal Science, could pave the way for ultra-low-power, high-performance integrated circuits essential for next-generation AI chips and advanced semiconductor applications.
Conventional transistors operate via thermionic emission of electrical charges, which requires a minimum gating voltage of 60 millivolts (mV). The Boltzmann limit makes subthreshold swing (SS) values below 60 mV per decade physically impossible at room temperature, restricting progress in high-performance electronics. The new TFET, developed by a team led by Prof. Jianhua HAO, Head of the Department of Physics and Materials and Chair Professor of Materials Physics and Devices at PolyU, uses quantum tunnelling to break this boundary.
'By adopting quantum tunnelling, our TFET breaks through this boundary, paving the way for ultra-low-power, high-performance integrated circuits essential for emerging AI chips and advanced semiconductor applications,' said Prof. Hao. The team created an ultra-thin heterostructure of alternating 2D bismuth and indium selenide layers using pulsed laser deposition. By precisely controlling the layer structure, the normally semi-metallic bismuth transforms into a semiconductor in its 2D form, allowing charge carriers to tunnel efficiently into indium selenide through quantum tunnelling.
The resulting TFET achieved SS values well below the 60 mV per decade limit. Operating at room temperature on silicon substrates, the device required a gate-voltage range of only 160 mV—far lower than the 800 mV originally required. This dramatic reduction in voltage could lead to significant energy savings in electronic devices, from smartphones to data centers.
Moreover, the device resolved a longstanding challenge in experimental TFETs by delivering a high output current alongside an exceptionally high ON/OFF current ratio. This combination is crucial for driving multiple downstream logic gates and diminishing circuit-delay, making the TFET more practical for real-world integrated circuits.
The implications for the semiconductor industry are profound. As AI models grow in complexity, the demand for energy-efficient computing has never been greater. Traditional transistors are approaching their physical limits, and this innovation offers a viable path forward. By enabling ultra-low-power operation, the TFET could extend battery life in mobile devices, reduce energy consumption in large-scale data centers, and facilitate the development of more powerful AI chips that do not overheat.
The research was conducted in collaboration with the National University of Singapore, The Hong Kong University of Science and Technology, Peking University, and the Singapore University of Technology and Design. This international effort underscores the global importance of advancing semiconductor technology.
While the TFET is still in the research phase, the successful demonstration on silicon substrates suggests that it could be integrated into existing manufacturing processes, potentially accelerating its adoption. The next steps will involve scaling the technology and addressing any manufacturing challenges, but the fundamental breakthrough has been achieved.
For business leaders and technology enthusiasts, this development signals a shift toward more sustainable, high-performance computing. As the world becomes increasingly reliant on AI and data-driven technologies, innovations like the TFET will be critical in meeting the computational demands of the future while minimizing environmental impact.
