Device Temperature On The Properties Of AlGaN Based Deep Ultraviolet Light-Emitting Diode

The short wavelength deep ultraviolet light source(200-300 nm)has a broad application in the water and air purification,medical sterilization,non-line-ofsight(NLOS)communication,high density optical storage and so on.Comparing with the traditional sterilization methods,such as alcohol disinfectant and hightemperature sterilization,the AlGaN based deep ultraviolet light-emitting diodes(DUV LEDs)can play a more important role in many situations where traditional sterilizations are not applicable,especially during the pandemic of COVID-19.However,DUV LEDs still have a huge gap in the light output power and efficiency,compared with the mature blue LEDs technology.Despite much effort in the development of DUV LEDs,there is few studies on the mechanism of temperature dependent device performance,and the device temperature and ideality factor as key parameters are often neglected.In this work,we study the device temperature on the properties of AlGaN based DUV LEDs from the experimental and theoretical aspects using the selfdeveloped LED test system and the advanced semiconductor simulation software APSYS.The main results are as follows:(1)In experimental aspect,we developed a new LED test system to study the behavior of a 280 nm AlGaN-based DUV LED,obtaining the electrical,optical,and thermal properties within one measurement for the first time.The physical properties of DUV LED devices with injection or temperature in the two stages of "constant temperature,injection change" and "constant injection,temperature change" are discussed respectively.The experimental results show that the light output power and wall-plug efficiency of the AlGaN-based DUV LED are strongly affected by device temperature.However,the ideality factor and series resistance would decrease with the device temperature.Studying the change of ideality factor would be helpful to analyze the state of carrier transportation in the device.(2)In device simulation,the device is simulated at various temperatures by APSYS software and the effects of device temperature on device performance,such as photoelectric characteristics,ideality factor,energy band structure,carrier concentration distribution and radiation recombination rate,have been systematically studied.The simulation results indicate that the high potential barriers inside the device is one key factor for the high value of ideality factor.In addition,the carrier can also obtain extra energy when the device temperature increases.On the one hand,it would help the carrier with higher energy overcome some potential barriers and make the ideality factor decrease.On the other hand,it also would aggravate the carrier overflow and lead to decrease of the device light output power.Therefore,the trade-off role of device temperature is needed to be considered in the development of DUV LEDs.(3)To further study the effect of device temperature on device performance,AlGaN based DUV LED devices with different Mg-doping concentrations are also simulated.Combined with the experimental results,the device performance of DUV LED is discussed under the Mg activation energy affected by device temperature.The results indicate that the carrier concentration inside the device is another key factor for the high value of ideality factor.Even if the devices are same in structure,the higher the carrier concentration,the lower the ideality factor value.Combining experiment and device simulation,this thesis reveals the physical mechanism of device temperature on the properties of AlGaN based DUV LED,which provides more experimental and theoretical basis for solving the negative effects of device temperature on the properties of DUV LEDs.This work would promote the development of DUV LEDs with higher efficiency and higher brightness.