Researchers at The Hong Kong Polytechnic University (PolyU) have engineered a novel tunnelling field-effect transistor (TFET) that overcomes the physical limits of conventional semiconductor technology, potentially revolutionizing energy-efficient computing and next-generation AI chips. The breakthrough, published in the journal Science, addresses the so-called “Boltzmann limit,” which has long constrained the energy efficiency of traditional transistors.
Conventional transistors operate via thermionic emission, requiring a minimum gate voltage of 60 millivolts (mV) at room temperature. This physical constraint, known as the Boltzmann limit, makes subthreshold swing (SS) values below 60 mV per decade impossible, limiting progress in high-performance electronics. The PolyU team, led by Prof. Jianhua HAO, Head of the Department of Physics and Materials and Chair Professor of Materials Physics and Devices, has circumvented this limit by adopting quantum tunnelling.
“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 2D bismuth and indium selenide alternating layers using pulsed laser deposition. By precisely controlling the layer structure, the normally semi-metallic bismuth transforms into a semiconductor in 2D form, allowing charge carriers to tunnel efficiently into indium selenide via 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 requirements could lead to significant energy savings in electronic devices.
Moreover, the device resolved a long-standing challenge in experimental TFETs by delivering a high output current alongside an exceptionally high ON/OFF current ratio. This dual achievement enables the transistor to drive multiple downstream logic gates, reducing circuit delay and improving overall performance.
The research, 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, marks a significant step forward in semiconductor technology. The implications for the industry are profound: more energy-efficient transistors could extend battery life in portable devices, reduce cooling requirements in data centres, and enable more powerful AI processors without escalating power consumption.
As the demand for AI and high-performance computing continues to grow, the ability to break through physical barriers like the Boltzmann limit becomes increasingly critical. This innovation not only demonstrates the potential of 2D materials in electronics but also provides a pathway towards more sustainable and powerful computing technologies.
