Study On Photon Extraction Efficiency Of ?-? Nitride-based UV LEDs

Due to its advantages such as fast switching,long lifetime,and narrow spectrum,?-nitride-based UV LEDs have a wide range of applications in UV curing,lithography,anti-counterfeiting detection,water purification,and medical diagnostics.However,there are still some bottlenecks in the development of high efficiency LEDs,which reduce the device's luminous efficiency and therefore hamper,the large-scale commercialization.The luminous efficiency of LED includes injection efficiency,internal quantum efficiency and external quantum efficiency.For UV LEDs,the reason for the low current injection efficiency is mainly due to the fact that existing epitaxial technologies have difficulty in obtaining AlGaN semiconductor materials with high carrier concentration and high conductivity;The reason for the low efficiency lies in that photons generated in the device cannot be extracted effectively due to total internal reflection and light re-absorption.So this work is based on how to improve current injection efficiency and light extraction efficiency.First,based on how to improve the internal quantum efficiency,this paper proposes the idea of replacing the p-AlGaN material by a conductive polymer PEDOT:PSS,and designs and prepares a PEDOT-nitride heterojunction structure.By analyzing the photoelectric properties of the device,It is concluded that PEDOT:PSS can replace the current difficult to prepare AlGaN materials for the preparation of UV LEDs.Second,based on how to improve the light extraction efficiency,a periodic nano-array structure is prepared on the light exit surface of the LED to improve the light extraction efficiency,and nano-pillars and nano-holes are prepared on the LED chip surface based on lithography and ICP etching processes.The structure,through the analysis of the photoelectric properties of the device,concluded that the nano-structured LED can significantly improve the light extraction efficiency,and the photoluminescence enhancement efficiency of the nanocolumn structure is greater than that of the nanopore structure,but the electroluminescence enhancement efficiency of the nanopore structure is greater than Nano-pillar structure experimental conclusions.And based on the Comsol multi-physics simulation technology,the near-field distribution of the nano-structured LED was simulated,and the improvement of the light extraction efficiency of the UV LED by the nano-structure was theoretically verified.All in all,this study uses nitride LED as the research system to explore the relationship between device structure,current-voltage characteristics and luminous efficiency.This study lays a theoretical and experimental foundation for further understanding of the LED light-emitting mechanism and improving luminous efficiency.