Investigations On Structure Optimization Of EBL And MQWs Of AlGaN-Based Ultraviolet Light Emitting Diodes

AlGaN-based ultraviolet light-emitting diodes(UV LEDs)have been widely applied because of continuous research and development of semiconductuor materials and devices.Various applications in new area have been developed gradually.At present,many applications have already been developed maturely,such as solid state lighting,disinfection system,water purification,and 3D printing and so on.The potential value of its applications is worth studying.Although AlGaN-based UV LEDs is always a research focus of numerous researchers,there are many difficult problems in improving optical characteristics and electrical characteristics of AlGaN-based UV LEDs,especially DUV LEDs with shorter wavelength.For example,terrible electronic leakage,the low carrier injection efficiency,the bottleneck of p-doping for AlGaN of high Al component,the difficulty of epitaxy technology for high-quality AlGaN,and the low light extraction efficiency and many other difficulties could result in low internal quantum efficiency(IQE),low light output power(LOP),and serious efficiency droop.The existence of these short boards could limit the applications and industrialiazation production of AlGaN-based UV LEDs.In order to improve the optical characteristics and electronic characteristics of AlGaN-based UV LEDs,many related researchers have done a great number of researches and have made some breakthrough progress.In this paper,we mainly focus on the problem to improve electron and hole injection efficiency of AlGaN-based UV LEDs.Firstly,we reviewed the development background of LEDs,introduced the basic characteristics of ?-nitride materials,and summarized the fundamental structure and working principle of LEDs.Then we collected the development and status of AlGaN-based UV LEDs at home and abroad.The development bottleneck of AlGaN-based UV LEDs was also investigated.In addition,we introduced the automated computer aided design(TCAD).Futhermore,we especially introduced the basic properities of the simulation software we used in our study,named Advanced Physical Models of Semiconductor(APSYS).Then we summarized the fundamental physical models and derived the fundamental mathematical physical equations involved in the simulation of our study.The basic operiation flow and some parameter setting principles were also summarized.We also investigated the measurement index of LEDs properities and made a brief introduction for every index.Focusing on the problem of improving the carrier injection efficiency of AlGaN-based UV LEDs,we first simulated the EL spectrum,light output power,IQE and other characteristics to research the influence of the change of Al composition in the barrier of superattice electron barrier layer(EBL)in AlGaN-based UV LEDs.From the simulation results,we found that when we linearly change the Al composition from 0.90 to 080 along the growth direction,the device will possess the best optical characteristics and electronic characteristics.Then we fully researched the mechanism of the improved properities by simulating their band structure,electric field intensity,electron and hole concentration and other physical parameters.Based on the optimized structure,we investigated the influence of Al composition of quantum barrier layer in active region of AlGaN-based UV LEDs by comparing the simulation results.First,we simulated the devices whoes Al composition changes in an V-shaped tendency and devices whoes Al composition changes in an inverted V-shaped tendency.By comparing their optical characteristics and electronic characteristics,we concluded the optimal structure of their own group.Then we combined the optical characteristics and electronic characteristics of the reference structure and found that the properities of the two optimal structures both can be improved in a certain degree comparing the reference structure.What's more,when the Al composition was set to 0.50-0.45-0.40-0.40-0.45-0.50,the device could be the optimum structure.We can also study the internal mechanism by analyzing their band structure and electric field intensity.