Less than two decades after smartphones fit into the palm of our hands, artificial intelligence is now running on devices worn on our wrists. The challenge is that while devices continue to shrink, the amount of data they must process and the number of functions they must perform are growing exponentially. A research team at POSTECH(Pohang University of Science and Technology) has found a promising way to address this contradiction.
A team led by Professor Byoung Hun Lee of the Department of Electrical Engineering and the Department of Semiconductor Engineering at POSTECH, together with Dr. Jae Hyeon Jun of the Department of Electrical Engineering, has developed a transistor technology that enables a single semiconductor device to perform multiple circuit functions simultaneously. The new approach significantly simplifies circuit design and increases data processing speed by fourfold compared with conventional methods. The findings were published in Advanced Functional Materials , an international journal in the fields of materials science and electronic devices.
One of the key challenges in the semiconductor industry is integrating more functions into smaller chips. As the number of functions increases, so do the number of circuits and transistors required. However, when adding new functions to previously fabricated semiconductor chips, back-end-of-line(BEOL), processing must be conducted at temperatures below 400°C to protect the existing chip structure.
The research team focused on zinc oxide(ZnO) and tellurium(Te). Both materials can be fabricated as thin, uniform films at temperatures below 200°C, making them promising candidates for next-generation semiconductor materials. By combining the two, the team created a ZnO–Te heterojunction transistor.
The device controls current flow in a highly distinctive way. Unlike conventional semiconductors, in which current generally increases as voltage rises, this device exhibits negative differential transconductance(NDT), in which current decreases over a certain voltage range. The team successfully realized double negative differential transconductance(D-NDT), in which this phenomenon occurs twice in succession within a single device. In simple terms, the technology allows a single device to handle tasks that would normally be divided among multiple devices, thereby reducing circuit complexity.
The key lies in precisely controlling the overlap length between the two materials. When the overlap region is short, the current changes only once. However, as the overlap region becomes longer, both lateral and vertical currents form simultaneously within the device, generating double current peaks. Just as a current flowing in a straight line becomes capable of more complex routing when it meets a three-dimensional intersection, the device becomes capable of more complex signal processing.
Using this device, the team implemented a frequency quadrupler that converts one input signal into four output signals. This function would typically require multiple transistors, but the new technology achieves it with a single device, reducing the number of required transistors by 75%. In actual circuit experiments, the researchers also confirmed that data processing speed increased fourfold within a single input signal cycle.
“This study demonstrates the possibility of implementing complex circuit functions at the level of a single device,” said Professor Byoung Hun Lee. “We expect this technology to be widely applicable to the development of ultra-compact AI devices and three-dimensional integrated, highly-density semiconductor systems.”
This research was supported by the Core Technology Development Program for the National Semiconductor Research Laboratory and the Nano-materials Technology Development Program, funded by the Ministry of Science and ICT and the National Research Foundation of Korea.
Advanced Functional Materials
Multi-Functional ZnO–Te Heterojunction Devices Enabling Compact Frequency Quadrupler
26-May-2026