University of Science and Technology of China has made important progress in semiconductor deep ultraviolet LED research

Recently, the research team of Haiding Sun and Shibing Long of the School of Microelectronics of the University of Science and Technology of China has achieved the above research breakthroughs by using the sapphire substrate chamfer angle to adjust the quantum well to achieve three-dimensional carrier confinement.

Although ultraviolet light accounts for only 5% of the energy of sunlight, it is widely used in human life. At present, ultraviolet light applications include printing and curing, coin anti-counterfeiting, skin disease treatment, plant growth light, and destruction of molecular structures such as bacteria and viruses. Therefore, it is widely used in air sterilization, water purification, and solid surface sterilization and disinfection.

Traditional ultraviolet light sources generally use the excited state of mercury vapor discharge to generate ultraviolet rays, which have many defects such as high power consumption, large heat generation, short life, slow response, and potential safety hazards. The new deep-ultraviolet light source adopts the light emitting diode (LED) light-emitting principle. Compared with the traditional mercury lamp, it has many advantages. The most important advantage is that it does not contain toxic mercury elements. The implementation of the "Minamata Convention" foretells that the use of mercury-containing ultraviolet lamps will be completely banned in 2020. Therefore, the development of a new environmentally friendly and efficient UV light source has become an important challenge facing people.

And deep ultraviolet light-emitting diodes based on wide-bandgap semiconductor materials have become the best choice for this new application. This all-solid-state light source system is small in size, high in efficiency, and long in life. Only a chip the size of a thumb cover can emit ultraviolet light that is stronger than a mercury lamp. However, it is not always easy to achieve high-efficiency luminescence of UV LEDs.

The research group of Professor Sun Haiding and Long Shibing of the School of Microelectronics of the University of Science and Technology of China has cleverly adjusted the bevel angle of the sapphire substrate to greatly increase the IQE of the UV LED and the luminous power of the device. The research team found that when the bevel angle of the substrate is increased, the dislocations inside the UV LED are significantly suppressed, and the luminous intensity of the device is significantly improved. When the bevel angle of the substrate reaches 4 degrees, the intensity of the fluorescence spectrum of the device has increased by an order of magnitude, and the internal quantum efficiency has reached a record-breaking 90%.

By optimizing the regulation of epitaxial growth on a substrate with a 4 degree bevel angle, the researchers found an optimal structure. The carrier lifetime of this structure exceeds 1.60ns, while this value in traditional devices is generally less than 1ns.

This research will provide new ideas for the research and development of high-efficiency all-solid-state UV light sources. This idea does not require expensive patterned substrates and complex epitaxial growth processes. It is expected that the luminous characteristics of UV LEDs can be improved to The height comparable to blue LEDs lays an experimental and theoretical foundation for the large-scale application of high-power deep ultraviolet LEDs.