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Light efficiency increased by 101.6%! Researchers developed ultraviolet LED usi

Published by admin October 12,2021

The United Nations Minamata Convention, which was signed by 128 countries and came into force in China in August 2017, bans the production, import and export of mercury containing products from 2020, including the production and sale of traditional mercury lamps.  It has become an urgent need in the field of sterilization, curing and exposure to develop a new type of ultraviolet solid state light source which is environmentally friendly and energy saving to replace the ultraviolet mercury lamp which is widely used at present.  UV LED based on the third generation semiconductor material AlGaN has obvious killing effect on the virulent novel Coronavirus, so it has been highly concerned at home and abroad.
 
 Different from mature blue LEDs, the core material of UV LEDs has lower In content and higher Al content, which leads to prominent problems such as high defect density In epitaxial layer, low hole concentration In p-AlGaN material, strong polarization effect, unbalanced carrier transport and so on.  Therefore, the luminous efficiency of UV LEDs is still much lower than that of mature blue LEDs.  When the emission wavelength is lower than 370nm, the emission efficiency of UV LEDs declines sharply, which becomes the biggest obstacle to their high-end applications.
 
 To solve the above problems, the Advanced Materials Platform of Semiconductor Institute of Guangdong Academy of Sciences has carried out systematic and in-depth technical research and development on UV LED from two aspects of material growth and device design.
 
 Firstly, high quality AlGaN materials and high internal quantum efficiency AlGaN quantum Wells were successfully prepared by MOCVD fine-growth mode regulation technology.  At the same time, the polarized field regulation technology and energy band engineering were used to introduce p-AlInGaN/AlGaN short-period superlattice material (SPSL) into the electronic barrier layer (EBL) structure of AlGaN based UV LED, and the UV LED devices with high internal quantum efficiency were successfully developed.
 
 The results show that SPSL-EBL can improve the carrier transmission characteristics of UV LED devices, and reduce the switch voltage of the devices, so that the emission efficiency of UV LED devices with the emission wavelength of 368 nm is increased by 101.6% compared with the traditional structure. This study will open up a new path for the research and development of high-efficiency solid-state UV light source.

Fig. 1 (a) Ultraviolet LED device structure diagram based on P-AlGaN /AlGaN SPSL-EBL;  

(b) 368 nm UV LED epitaxial wafer (left) and chip image on the wafer (right).  

 

Figure 2 (a)- (d) and (e)- (h) are respectively STEM diagrams of UV LEDs with traditional structure and SPSL-EBL structure.
 The crystal quality of the two kinds of samples is good and the interface of heterojunction is clear.
 (j) and (k) are the lighting photos of traditional UV LED based on SPSL UV LED under the forward current injection of 200mA, respectively.
 The UV power of chip B is 101.6% higher than that of the conventional UV LED