ABSTRACT
Deep ultraviolet light-emitting diodes (DUV LEDs) are promising light sources for disinfection, especially during the pandemic of novel coronavirus (COVID-19). Despite much effort in the development of DUV LEDs, the device temperature and ideality factor are key parameters of devices, which are often neglected. Here, we developed a simple and convenient method to study the behavior of a 280 nm AlGaN-based DUV LED, obtaining the electrical, optical, and thermal properties within one measurement. From the experimental results, we find that the light output power and wall-plug efficiency of the AlGaN-based DUV LED are strongly affected by device temperature, ideality factor (beta), and series resistance (R-s). beta decreases from 9.3 to 8.1 at 40 mA when the temperature increases from 302 to 317 K. We compared these results with simulations and found that the high potential barriers inside the device and the carrier concentration in n-type or p-type layers, especially the hole concentration in p-type layers, are the two key factors for the high value of the ideality factor from the LED structure. As the device temperature increases, carriers with higher energy would overcome some potential barriers and Mg acceptor activation would be more efficient, which are beneficial for carrier transportation. However, these also lead to the carrier overflow and weaken the radiative recombination rate. The trade-off role of device temperature in carriers between transportation and overflow is needed to be considered in the future development of DUV LEDs with higher efficiency and higher brightness.
ABSTRACT
Objective: To sum up the experience of healthcare-acquired infection control against coronavirus disease 2019 (COVID-19) in Wuhan by a medical team from Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, so as to provide reference for the contain strategy of sudden infectious diseases in China. Methods: The whole process of prevention and control of HAI was implemented through methods such as management organization construction, institutional establishment and implementation, personnel training, occupational exposure planning, and introduction of hightech methods. Results: There were a total of 136 members in the medical team, including 30 doctors, 100 nurses, and 6 administrative staffs. None of them were infected with COVID-19, achieving zero infection among medical staff. Conclusion: Although the task of assisting Wuhan was tight in time, and materials and heavy, under the leadership of the team leader and the cooperation of all the staff, all measures were implemented, the training covered all the staff, and high-tech means were introduced to optimize the control strategy, achieving the goals of zero infections among medical staffs and zero cross infections among patients.