A multifunctional three-terminal diode (TTD) developed by a team at the University of Science and Technology of China (USTC) can function as both an optical emitter and a photodetector. The TTD boosts communication bandwidth significantly. It is easily reconfigured, making it useful for integrated optical computing. According to the researchers, it sets a new benchmark in light emission and detection control. The TTD consists of a traditional two-terminal, gallium nitride (GaN)-based p-n diode with a monolithically integrated third terminal (Tt) that is composed of a metal/aluminum oxide (Al 2O3) dielectric layer placed directly on the p-layer. When the TTD is operated as an optical emitter, its light intensity can be tuned by adjusting the bias applied to the Tt. The TTD’s modulation bandwidth can be increased from the 160 megahertz (MHz) available in the original p-n diode to 263 MHz. This increase is possible because of the integrated bias tee function enabled by the Tt and represents a 64% boost in modulation bandwidth compared to conventional systems. The TTD’s innovative design eliminates the need for external bias tee circuits, reducing signal loss and enhancing overall performance. A team of researchers at USTC, led by professor Haiding Sun and including colleagues at several international institutions, developed the TTD, a multifunctional three-terminal diode that functions as both an optical emitter and a photodetector. Courtesy of M.H. Memon/University of Science and Technology of China. When the TTD is switched to detector mode, both the applied voltage on the Tt and the incident light act as signal inputs that control the magnitude of output photocurrent, providing reconfigurable optoelectronic NAND and NOR logic gates. The TTD enables reconfigurable optoelectronic logic operations without the need for structural changes. It can be easily reconfigured by adjusting the voltage across the diode. The TTD’s reconfigurability make it well-suited for use with integrated optoelectronic chips. The increase in modulation bandwidth that can be achieved with the TTD could advance applications in optical wireless communication where high speed and efficiency are critical, such as light fidelity and non-line-of-sight communications. The diode’s ability to boost computing performance could be valuable in high-speed data transmission applications for optical communications. Integrated optoelectronics, optoelectronic logic operations — almost any application or sector requiring high-speed, multifunctional optoelectronic devices — could benefit from the TTD’s high-performance light emission and photodetection capabilities. Two-terminal devices have been the building blocks of modern electronic systems, but the typical two-terminal architecture can limit functionality and performance. The TTD’s dual functionality is a significant improvement over conventional two-terminal devices. By performing multiple functions within a single device, the TTD reduces system complexity and improves the performance of optoelectronic systems, clearing the path to more compact and efficient technology. The USTC team collaborated with colleagues at Fudan University, the Chinese Academy of Sciences, The Australian National University, King Abdullah University of Science and Technology, and Wuhan University to develop the TTD. The research was led by professor Haiding Sun at the iGaN Lab at USTC. The research was published in Nature Electronics (www.doi.org/10.1038/s41928-024-01142-y).