Views: 3 Author: Site Editor Publish Time: 2023-03-13 Origin: Site
It can be used for the manufacture of high-power UV LED, and the technology of the Japanese team is bright
Recently, a Japanese team of engineers announced that they had invented an insulating substrate stripping method. By immersing the device sample in a water environment with a temperature of 115 ° C and a pressure of 170 KPa, the AlGaN LED device was separated from the substrate.
This method is jointly developed by Meiji University, Mitsubishi University and Osaka University in Japan. It can make AlGaN LED peel off as easily as using laser stripping technology to peel off high-power GaN devices.
Based on this idea, the Japanese engineer team began to consider how to penetrate water into the crystal gap of hundreds of nanometers. At first, all attempts were hindered by the surface tension of water. In order to solve this problem, the research team proposed a new method: immerse the sample into a beaker filled with water, and then put it into a closed polycarbonate container, which is emptied and kept in vacuum for 5 hours.
The above figure shows the cross section transmission electron microscope image of AlGaN-based heterostructure, indicating that the AlN nanopillar area has been peeled off. Yanwu Yuanming said that the key to the success of the whole scheme is mainly the use of pressurized water. From the transmission electron microscope, the 1cm2 sample made by the team has almost no additional dislocation. Based on this, if the experimental method is further optimized, it can be used for mass production of AlGaN-based devices.
Silanna UV technology is conducive to the manufacture of shorter wavelength ultraviolet LED
On September 15, 2022, Silana UV announced a breakthrough in UVC-LED technology, providing a huge advantage analysis for disinfection, water quality monitoring, gas sensing, liquid chromatography, chemical and biological applications.
It is understood that the breakthrough patent of Silanna UV technology is that the short-period superlattice (SPSL) method has overcome many difficulties that have troubled the competitive AlGaN UVC-LED technology. In essence, Silanna UV has effectively created a new material, a nanostructure, which is easier to control and has far better characteristics than traditional AlGaN.
Silanna UV uses a different method to generate ultraviolet light. Silanna uses short period superlattice (SPSL) technology to replace the common AlGaN method. It is reported that in this method, instead of using coarse old ternary alloys, the alternating layers of AlN and GaN (up to hundreds of layers) are carefully constructed to create the so-called SPSL. Unlike traditional ternary alloys, the key characteristics of this SPSL - including band gap and conductivity - can be fine-tuned by simply adjusting the thickness of the constituent layer. This means that the problems caused by high Al content AlGaN have been alleviated, especially the poor electrical characteristics and short wavelength optical loss of the old method.
SPSL technology makes Silanna UV have great advantages over UVC-LED competitors, including maintaining high power at short wavelengths, excellent electrical characteristics and excellent service life performance.
Peking University team prepared high-quality p-type AlGaN short-period superlattice
The team of Shen Bo and Xu Fujun from the State Key Laboratory of Artificial Microstructure and Mesoscopic Physics of Peking University and the Wide Band Gap Semiconductor Research Center has innovatively developed a method of "desorption control ultra-thin layer epitaxy", successfully solved the problem of controllable preparation of high Al component AlGaN epitaxial layers with sub nanometer thickness, and realized high Al component AlGaN epitaxial layers with three single atomic layers (about 0.75 nm) in thickness, On this basis, high-quality p-type AlGaN short-period superlattices were prepared.
At the same time, this method is beneficial for Mg atoms to occupy the vacancy generated by the desorption of Al and Ga atoms and merge into the lattice, which can effectively increase the doping concentration of Mg in the epitaxial layer of AlGaN.
The hole concentration at room temperature of p-type AlGaN short-period superlattices (the equivalent Al component is more than 50%) based on this method reaches 8.1 × 1018 cm-3。The ionization energy of Mg acceptor in AlGaN was determined to be 17.5 meV by variable temperature Hall experiment, which achieved a significant reduction of the ionization energy of Mg in AlGaN. More importantly, the sub-nanometer ultra-thin barrier layer ensures the formation of microstrip in the superlattice and provides a channel for the longitudinal transport of holes.
When the p-type AlGaN superlattice structure is applied to deep UV LED devices, the carrier injection efficiency and light extraction efficiency (combined with high-reflectivity p-type electrode) of the device are significantly improved, and the output power reaches 17.7 mW at 100 mA.
The intensity of deep ultraviolet luminescence is nearly 2 times higher. The team of Xiamen University designed an artificial nanostructure
The research team of Xiamen University has innovatively designed an artificial pyramid/plate-shaped nanostructure. Through the combination of nanoimprinting, dry etching technology and wet etching technology, the (AlN) 8/(GaN) 2 active layer with a luminescent wavelength of 234 nm forms (0001), (10-13), (20-21) and other groups of crystal planes with fine and controllable angles. Interestingly, these crystal planes can control the propagation and extraction mode of deep UV light waves in nanostructures, effectively break through the limitation of small cone angle of outgoing light in traditional planar structures, and greatly improve the extraction efficiency of deep UV light.
The results showed that the polarized light of TM and TE increased by 5.6 times and 1.1 times respectively compared with the plane structure, and the total luminous intensity at 234 nm wavelength of deep ultraviolet was increased by nearly 2 times. This research work provides a new idea for improving the efficiency of deep ultraviolet short-wave light-emitting devices, and is expected to expand to the photoelectric devices such as micro-size LED and deep ultraviolet detector.
The optical power of the device has been increased by 55%, and the service life has been nearly doubled. Another technology released by Xiamen University
A new study from Xiamen University announced that the team of Professor Cai Duanjun of Xiamen University and Professor Li Junji of Quannan University of South Korea worked together to propose a new and efficient hydrogen removal technology driven by local strong electric field of chloride ion. Through the application of this technology, the conductivity of p-AlGaN and the photoelectric performance of deep ultraviolet LED have been significantly improved, with the optical power of the device increased by 55% and the life of the device nearly doubled.
It is reported that the team used electrochemical methods to apply a local strong electric field in semiconductors, using semiconductor wafers as anodes in a solution environment, using the highly concentrated chloride ion layer adsorbed on its surface. Using this method, this work successfully achieved efficient hydrogen removal for a variety of semiconductor materials, including GaN, AlGaN, SiC, AllnP and complete deep UV LED wafers, with a maximum hydrogen removal rate of 52%.
More importantly, the application of this new directional electric field hydrogen removal technology can effectively activate the acceptor activity of Mg in p-type AlGaN with high Al content, greatly improve the p-type conductivity, in which the current increases by 8.8 times, the hole concentration increases by an order of magnitude, and the electrode contact resistance decreases by an order of magnitude. Further applying this technology to 273 nm AlGaN-based deep UV LED, the photoelectric performance of the device has also been significantly enhanced. Among them, the switching voltage of LED is reduced by 1 V, and the optical power is increased by 55% at most, reaching 9.8 mW at the current of 100 mA, and the efficiency of wall insertion is significantly increased by 62%, reaching 3.3%. Moreover, the reliability of UVC-LED has also been improved, and its service life has been nearly doubled.
