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"We first proposed and realized a photodiode based on field-effect modulation, and demonstrated its great potential in optical communication and optical logic operations," said Professor Sun Haidong from the University of Science and Technology of China.

Recently, his team's paper was published on the cover of the current issue of Nature Electronics.

He stated: "Among all the cover papers published in Nature Electronics, we found that on average, there is only one paper from Mainland China selected as a cover paper every year or so, and sometimes it takes about two years."

Therefore, the publication of this cover paper has made the entire research group feel honored and motivated.

In the research, the research group used a monolithic integration method to create a capacitor structure made of "metal-oxide-insulator-semiconductor" on the p-type conductive layer of a gallium nitride-based ultraviolet light-emitting diode.Through this, they constructed a light-emitting diode with three ports and provided it with the symbol of a new device.

While applying a bias to the original light-emitting diode, when a specific working voltage is configured on the third port, this three-terminal photodiode can demonstrate unique working modes and states, thus being able to act as a tunable light emitter or a multifunctional photoelectric detector.

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When the three-terminal diode operates as a light emitter, due to the integration of the "biaser" function on the third port, the output optical power can be regulated by the bias voltage of the third electrode.

Therefore, when it is connected to an optical communication system, it can achieve the same function as a conventional light-emitting diode connected with an external biaser.

Compared with systems using external biasers, the three-terminal diode has a higher frequency bandwidth due to its ability to reduce parasitic capacitance, with an enhancement of up to 60%, reaching the international highest level for devices of the same size.Sun Haidong stated that the introduction of this three-terminal diode not only reduces the demand for external bias circuitry in optical communication systems but also achieves smaller and wider bandwidth optical communication systems.

Interestingly, when the three-terminal diode switches to the photodiode mode, it is simultaneously controlled by the voltage applied to the third port and the incident light, thus enabling the implementation of reconfigurable high-speed optoelectronic logic gates, such as "NAND" and "NOR."

Moreover, when switching between different logic gates, there is no need to make any changes to the structure of the device itself.

Based on the universal logic gates NOR and NAND, any logical Boolean expression can be generated, and at this time, a complete logic circuit can be formed using the same device.

In the research, they not only achieved performance improvement but also integrated the "bias" of the traditional optical communication system into the device's third electrode based on monolithic integration technology. This not only improved the communication bandwidth performance of the device but also significantly reduced the volume and area of the optical communication system.This is conducive to further promoting the development of the next generation of high-speed, compact, multifunctional optoelectronic integrated chips and systems.

Due to the simple structure and manufacturing process of this device, the new field-effect modulated photodiode architecture proposed in this paper can be widely used in active optoelectronic integrated chips and devices made of various semiconductor materials, promoting the development of the next generation of high-speed, multifunctional optoelectronic integrated chips.

Break through the existing technical bottlenecks and limits of electronic systems.

It is understood that with the arrival of the era of artificial intelligence and the deepening development of digital transformation, people's demand for semiconductor chips with high data transmission speed and high data computing performance is continuously increasing.

Driven by the demand for high-speed data transmission and processing, integrated circuit chip technology has shown a trend of high integration and diversification.Among them, the potential of optoelectronic integrated chips that use photons as information carriers and their related technologies is being continuously explored and developed.

Optoelectronic chips are a new type of chip architecture composed of various basic elements such as optoelectronic devices and microelectronic devices.

They can convert, transmit, and process signals in various forms such as electricity and light, and are expected to blend and complement traditional integrated circuit devices, overcoming the limitations and bottlenecks of device physical size brought by Moore's Law.

Among them, as a necessary component in optoelectronic integrated chips, photodiodes have been widely used in light-emitting units and detection units.

However, existing photodiodes all require corresponding external driving circuits, only in this way can the conversion between electrical signals and optical signals be realized.This architecture greatly restricts the signal transmission speed and bandwidth of the entire optoelectronic system, and inevitably increases the system's volume and complexity, thereby limiting the integration and development of optoelectronic technology.

Therefore, how to break through the traditional model and overcome the bottlenecks and limits of existing electronic system technology has become a research focus in the field of optoelectronic integration.

The Pakistani student has not returned to his homeland for several years, and his classmates in the country left just before the New Year.

Over the years, Sun Hai has been deeply involved in the field of gallium nitride materials and devices, and has been working hard to study their applications in the fields of solid-state lighting, display imaging, and detection.At the same time, he and his research group are also very concerned about the expansion of such technologies in emerging fields of optoelectronic integration and optical communication, optical computing, etc.

When researching the UV micro-LED-based blind light communication system, they found that the bias-tee in the light signal transmission module is crucial for effective signal transmission during the construction and testing process.

To meet the needs of the system construction, the team tried all models of bias-tees on the market.

However, the huge system is always very troublesome to build, and its modulation bandwidth performance is easily affected by the quality of the bias-tee module.

One day, they sat together to discuss how to simplify and optimize the blind light communication system.At this point, Sun Haidong and student Yu Huabing, along with the Pakistani international student Muhammad Hunain Memon, suddenly had a brainstorm: considering that the bias itself is a "component or circuit module," could the bias be directly integrated into the light-emitting diode light source through monolithic integration technology?

However, implementing the functions of the bias with capacitors and inductors directly on the gallium nitride wafer does not seem to be a wise idea, as this solution would make the chip preparation process more complex, and the performance of the capacitors and inductors cannot be guaranteed, while also seriously affecting the quality of optical communication.

Suddenly, Yu Huabing casually said: "Why make it so complicated? Why not use the classic field effect in semiconductor devices to achieve signal modulation functions?"

At this moment, Sun Haidong's mind emerged with the structure of combining the light-emitting diode with a "new functional electrode" (i.e., the "third electrode" in the paper).

In the traditional sense, the field-effect transistor based on the classic structure of metal-oxide-semiconductor (MOS) can itself achieve the opening and cutting off of the transistor channel by effectively controlling the voltage applied to the MOS.So they thought: If a similar structure is combined with a light-emitting diode (LED), it might play a similar modulating role.

However, this is about regulating the luminescent properties of the LED, which will generate new control mechanisms and phenomena.

Subsequently, they immediately determined the device structure and manufacturing process. Soon, the research team created the first three-electrode diode sample and verified the control effect of the third electrode in the sample.

Although this process only took a month, they also faced many doubts: Does this field effect really exist? Is the modulation effect caused by leakage from the third electrode? What is the mechanism of this modulation effect? Does this structure really have application prospects?

During the three years of this project, they repeatedly questioned themselves and answered these questions through experiments and tests.During this period, Muhammad Hunain Memon was unable to return to his homeland, Pakistan, for testing purposes. Yu Huaibin would always be the last one to go home for the New Year, and during the New Year, Yu Huaibin would pass the testing baton to Muhammad Hunain Memon.

Ultimately, they developed up to a dozen rounds of device processes, continuously designing and attempting based on the structure of light-emitting diodes at various wavelengths, with the third electrode.

After a large number of experiments and repeated confirmations, it was proven that the third electrode indeed has a modulating effect on light-emitting diodes.

It was also found that the diode structure with the third electrode can use the field effect to control the photogenerated current. When used in optoelectronic logic gate circuits, it is also expected to provide a better prototype basis for the implementation of optical computing.

Sun Hai Ding added: "In the experiment, my mentor, Academician Liu Sheng, provided guidance on some key technical details, including how to construct the device electrodes, the material growth process, and the monolithic integrated packaging of the device. He also guided us to carry out industrial layout, including patent applications, etc."Ultimately, the related paper was published under the title "A three-terminal light emitting and detecting diode" in Nature Electronics[1].

Muhammad Hunain Memon and Yu Huabing are the co-first authors, and Academician Liu Sheng from Wuhan University and Professor Sun HaiDing from the University of Science and Technology of China are the co-corresponding authors.

It is also reported that Sun HaiDing named his laboratory "iGaN Laboratory," which is closely related to the original intention and mission of the research group.

GaN is the chemical formula for gallium nitride, and Sun HaiDing personally believes that gallium nitride is one of the most perfect semiconductor materials besides silicon.

The "i" represents imagination, innovation, and importance. "This is our iGaN. YES, We CAN!" said Sun HaiDing.It is also reported that optoelectronic chips and integration serve as a supplement to traditional electronic integrated systems and have always been the focus of Sun Haiding's laboratory.

He believes that gallium nitride is the "silicon material" in the field of wide bandgap semiconductors, possessing many characteristics that silicon does not have, such as luminescence, and it can emit light from ultraviolet to infrared.

Therefore, whether in the field of optoelectronics or in the traditional power electronics field, gallium nitride can exert tremendous power.

In the field of optoelectronics, the invention of gallium nitride-based blue light-emitting diodes has changed human lighting habits (replacing traditional incandescent lamps), and the relevant scientists were also awarded the 2013 Nobel Prize in Physics.

But this is just the beginning of the "shining and heating" of the gallium nitride optoelectronic industry, and the prospects for gallium nitride and its related devices are very bright in the future.At present, the research team has also started cooperation with the leading enterprises in the field of gallium nitride optoelectronics in China. This project has also been supported by national-level projects (including the National Key Research and Development Plan and the National Natural Science Foundation of China projects, etc.).

At the moment, they are communicating and cooperating with the industry, hoping to industrialize the devices and technologies as soon as possible.

Sun Haidong said: "We also hope that this research can promote the development of the next generation of high-speed and multifunctional optoelectronic integrated chips, bringing new technical solutions to the fields of optoelectronics, optical communication, and optical computing."