Photothermal Properties Of AlGaN-based UV LED And Its Package Structure

Ultraviolet LED(Lighting Emitting Diode)is affected by total reflection effect,polarization characteristics of epitaxial materials,etc.,so problems such as low light extraction efficiency and poor heat dissipation ability are common.In this paper,UV LED devices are prepared and tested by static electricity,high temperature and humidity,and aging.It is found that the reliability of the devices is poor and the life is short,only 508h～2281.3h.Therefore,it is necessary to improve the optical and thermal performance of the devices.At the same time,simulation method is adopted in this paper,in order to save the materials and time required by the experiment,from the chip and package structure to study the optical performance of the device.First,by comparing the light extraction efficiency and light output intensity of the five new epitaxial sheet structures and optimizing the relevant parameters,the best performance of the new structure is obtained when the height and width of the Al N groove are 150 nm and 180 nm,the height of the Al N cylinder is 300 nm,and the semi-circle radius and spacing of the sapphire substrate are 300 nm and 570 nm.Secondly,in the study of planar packaging layer devices,when the refractive index of top and side packaging layer is 1.7 and 1.6,respectively,the transmittance reaches the maximum.In double-layer packaging,no matter semicircular packaging or plane packaging,interface total reflection,light migration,Fresnel reflection and other factors affect light extraction.Thirdly,by doping Al N nanoparticles at the side of the packaging layer,the device can obtain the maximum optical extraction efficiency when the particle diameter is 30 nm and 10 nm,and the doping ratio is 0.9% and 0.11%,respectively,in TE and TM optical modes.Fourthly,columnar etching of inorganic encapsulated glass shows that the optical performance of the device is the best when the pattern height is 200 nm and the period is 120 nm.In the aspect of thermal simulation,firstly,the thermal performance of ceramic and metal scaffolds,different chip types and different substrate models is compared,and the heat dissipation performance of ceramic scaffolds,flip chips and high thermal conductivity substrate models is the best.Second,adding copper holes with a spacing of 0.4mm and a diameter of 0.35 mm below the electrode of the ceramic support can obtain better heat dissipation effect.Third,when the length and width of the heat sink are 1mm and 0.5mm,the heat dissipation performance is the best;Fourthly,the heat transfer adhesive with length of1.2mm is added to the solidifying area below the chip,and the heat dissipation effect of the model is the best.Fifth,when the chip size and the solid layer size are changed to 1.1mm and1.3mm respectively,the junction temperature and thermal resistance are the minimum values.Sixth,when the power is less than 0.5W,using 0.25W/m·K and greater than 0.5W,1W,1.5W,3W using more than 1W/m·K,2W/m·K,7W/m·K solid adhesive can meet the conditions of stable working state.This paper has made some achievements in improving the optical extraction efficiency of the device and reducing the working temperature of the device,which provides a new idea for the subsequent research on the structure design and device efficiency of the ultraviolet LED,and plays a driving role in the development of the ultraviolet LED.