Design Fabrication Of High Power LED With Current Blocking Layer And Sutdy On It's Characteristics

As the fourth generation lighting source,the light-emitting diodes(LED)has many advantages,such as high luminous efficiency,long service life,energy saving and environmental protection.It is an important breakthrough in the development of electric light sources.And as the core of LED light source,the quality of LED chip directly determines the performance,life and so on.Therefore,the improvement of optical extraction efficiency is the key step to promote the development of LED chip technology when the third generation wide band gap semiconductor materials have been widely used,the internal quantum efficiency has reached a fairly high level.In this paper,we study the principle of improving the efficiency of high power LED light extraction by current blocking layer and the key fabrication process of LED with CBL structure.The thermal characteristics,photoelectric parameters and reliability analysis of LED with CBL structure are carried out.This paper is supported by the National Key R&D Program of China(No.2017YFB0403100,2017YFB0403102).The main research contents are as follows:(1)The layout of CBL high power LED was designed,and the key process of device fabrication is optimized.the influence of different masks on ICP etching was studied.The sputtering and annealing conditions of ITO were studied in order to achieve the best annealing conditions.The corrosion and peeling processes of ITO were compared.Two kinds of high power LED chips with or without CBL structure were prepared by optimizing the process conditions.And the photoelectric parameters of the bare core are tested under 350 mA.(2)The two kind of high-power LED were packaged,and the photoelectric parameters of two samples under different currents were tested.Four samples were randomly selected from each devices,At first,the photoelectric parameters of the device under 25?,350 mA working current are tested.Then the photoelectric parameters of two kinds of devices under different currents are tested.The improvement effect of CBL structure on the light output power and Luminous efficiency of the device under thedifferent currents is analyzed.The influence of CBL structure on the spectrum and color rendering performance of the device is analyzed.Finally,the influence of inserting CBL structure on the voltage of the device is analyzed.(3)The photoelectric parameters and thermal characteristics of the two samples were tested at different temperature.The change of light output power with temperature is analyzede.The change of color temperature with temperature of the two samples was analyzed,and the reason why the color temperature of LED with CBL structure was lower was studied.The changes of half-width and peak wavelength of two kinds of LED are analyzed.The forward voltage change of two kinds of LED devices is also analyzed.Finally,the junction temperature and thermal resistance of two kinds of devices is tested.The influence of CBL structure on the thermal characteristics of the device is analyzed.(4)Experiments on accelerated aging of two devices with and without CBL structure were carried out.Five samples were selected from each devices,the temperature was 85 ? and the driving current was 350 mA.The change of photoelectric parameters of two kinds of devices with aging time is analyzed.Combined with the analysis of the chip morphology observed under the device and microscope,the failure mechanism of LED chip was analyzed.