2024-07-16
한어Русский языкEnglishFrançaisIndonesianSanskrit日本語DeutschPortuguêsΕλληνικάespañolItalianoSuomalainenLatina
What do you think of when you think of diodes? The small flashing light on your phone charger? The infrared "eyes" on the front of your remote control? These are all common applications of diodes in our daily lives. As a basic component of electronic circuits, diodes are like a "checkpoint" on a one-way street, allowing current to pass in only one direction (rectification). This seemingly simple function plays a key role in countless electronic devices.
In fact, the potential of diodes is far more than that. Professor Sun Haiding's iGaN Lab research group at the University of Science and Technology of China and Academician Liu Sheng of Wuhan University and his team have recently developed a multifunctional photodiode, which has brought the application prospects of diodes to a whole new level.
This article was published as a cover article in Nature Electronics
(Image source: Reference 1)
This new multifunctional diode,It can not only rectify like a normal diode, but also emit light like a light-emitting diode (LED), and it also has the ability of photoelectric detection and logical operation.It is truly "killing three birds with one stone"! It was unimaginable in the past to realize multiple functions in one diode.
The core of this "super diode" is a gallium nitride-based PN junction. As we all know, the PN junction is the "heart" of the diode, composed of two types of semiconductors, p-type and n-type. When a forward voltage is applied to both ends of the PN junction, electrons and holes will meet at the junction and "recombine", thereby generating current and turning on the circuit.
If this recombination process releases photons, the PN junction becomes a light-emitting diode, which can convert electrical energy into light energy. And gallium nitride is a material that is naturally suitable for making LEDs.
Three colors of LED
(Image source: Wikipedia)
Gallium nitride is an emerging wide-bandgap semiconductor. Compared with traditional silicon and germanium, it is like a "big guy", and electrons need more energy to cross its energy band "gap".
This gives GaN many advantages:It can withstand higher voltages, temperatures and frequencies, and is suitable for manufacturing high-power, high-frequency and high-temperature devices; its bandgap width corresponds to the wavelength of blue-violet light to ultraviolet light, and is an ideal material for manufacturing short-wavelength LEDs and lasers; it can form band-adjustable compounds with a variety of elements, facilitating monolithic integration (integrating multiple functional devices on the same piece of semiconductor material to form a complete system or subsystem).
With these unique physical and chemical properties, gallium nitride shines in lighting, display, communication, power electronics and other fields, and is hailed as the "star" of the third-generation semiconductors.
This time, researchers made a seemingly small change based on gallium nitride LEDs: adding an independently controllable third electrode above the p-type region of the PN junction. It is this ingenious design that gives the diode more room for imagination.
Schematic diagram of the new diode
(Image source: Reference 1)
By applying different voltages and regulating the contact between the electrode and the p-region, the carrier concentration in the PN junction region can be controlled, thereby adjusting the luminous intensity and detection sensitivity of the device. Even better, the two control signals can also simulate the input of the logic gate, allowing the diode to have the ability of logical operation.
Seeing this, many readers may be confused and start to back off. Don’t worry, we will now “translate” the above words into language that everyone can understand.
In traditional gallium nitride LEDs, the PN junction is like a "two-person stage" where electrons in the n-region and holes in the p-region meet and recombine, releasing photons at the same time, which manifests itself as bright light on a macroscopic scale.
The rhythm of this "dance" is mainly controlled by the voltage applied to the two ends of the PN junction. The higher the voltage, the faster the electrons and holes "dance", and the greater the luminous intensity. But in addition to adjusting the brightness, this "stage" does not seem to have any other functions.
The innovative designs of Chinese researchers have given this "stage" new capabilities.They added an independent third electrode above the p region. This electrode, like a "stage manager", can provide additional control over the "dancers" without affecting the "performance" of the PN junction.
Specifically, when a negative voltage is applied to the third electrode, it acts like a "vacuum cleaner" to attract holes near the p-region. The departure of holes is like fewer "dancers" on the stage, which will reduce the hole concentration in the entire p-region.
As the majority carriers in the p-region, the change in the concentration of holes will significantly affect the electrical properties of the PN junction. A decrease in hole concentration means that the conductivity of the p-region becomes worse, the resistance of the PN junction increases, the probability of "encountering" between electrons and holes decreases, and the luminescence intensity will weaken. Conversely, if a positive voltage is applied to the third electrode, more holes will be pushed to the p-region, enhancing the luminescence of the PN junction.
Although adjusting the third electrode has a similar effect to adjusting the overall voltage, its regulation effect is more precise and the energy loss is lower.
That's not all. The addition of the third electrode gives it new applications in photoelectric detection. When the diode is working in reverse bias, the electric field inside the PN junction can separate the photogenerated electron-hole pairs, generate photocurrent, and realize the detection of light signals. The third electrode can change the strength of the built-in electric field of the PN junction by adjusting the hole concentration in the p-region, thereby affecting the size of the photocurrent. This is equivalent to a "zoom lens" that can adjust the photoelectric response sensitivity of the diode as needed.
What is even more amazing is that when the third electrode and the PN junction are considered as a whole, this device can simulate logic operations! Imagine that we can regard the voltage applied across the PN junction as an input signal, the voltage of the third electrode as another input signal, and the current output of the diode as the logical result.
By cleverly designing the circuit and adjusting the high and low levels of the two input signals, the diode can perform basic logic operations such as "AND", "OR" and "NOT". This is equivalent to upgrading a simple "stage" into a multifunctional "studio center"!
Of course, there are still many challenges to overcome before this technology can be applied, such as further optimizing device performance and improving the reliability and consistency of the manufacturing process. But there is no doubt that the emergence of this multifunctional gallium nitride diode indicates that a more exciting optoelectronic world is quietly approaching.
In this world, light emission, detection, and computing are no longer clearly separated, but perfectly integrated and closely coordinated within a device. We have reason to believe that this groundbreaking research result will bring revolutionary changes to the future fields of lighting, display, communication, and computing.
One device, multiple functions.This is not only a technological innovation, but also represents a brand new way of thinking. The "three-in-one" gallium nitride diode tells us that with clever design and cross-border integration, a seemingly ordinary device can also release extraordinary potential. This also tells us that whether in scientific research or other fields, breaking the inherent boundaries and daring to explore and innovate can always bring unexpected surprises.
references:
Produced by: Science Popularization China
Author: Guo Fei (Yantai University)
Producer: China Science Expo
Collect and organize the latest news information and make it available for free for everyone to read
