The Fabrication And Thermal Analsys Of GaN Based High Voltage LED

LED(lighting emitting diode), as a new and efficient solid state lighting device,has the advantages of energy saving, environmental friendly and high reliability, it’s ahuge improvement of human lighting history. As the traditional LED driverrequirements are relatively harsh, that spawned a new research on high-voltage LED.Firstly, this paper makes a brief introduction about the development and theapplication of LED and wealso make a research about the critical process ofhigh-voltage LED fabrication, after fabrication is finished, the devices are electricaland optical tested, the new HV LED layout was designed. The finite element analysissoftware―ANSYS‖simulates the temperature of key parts of high-voltage LED, thispaper also focuses on the HV LED thermal resistance and thermal imager and the heatdistribution.This paper was supported by the National Key Technologies R&DProgram (No.2011BAE01B14). The main research work and achievements are asfollows:(1) The critical process of GaN-based HV LED fabrication was studied. Thenhow the parameter of ICP impact the etched GaN deep groove’s angle was analyzed,and the groove inclination angle of the LED influence yield was studied; The methodof how to make less pinhole and compact SiO2layer deposited by PECVD wasexplored, and how the CBL impact the LED was also studied; The effect of annealingconditions on influence the LED series resistance was analyzed. the resistivity is thelowest at30minutes of annealing at550℃by comparison of the experimental data.(2) The12V blue and green HV LED and the50V blue HV LED were fabricated,the electrical characteristics was tested and the optical characteristics of50V HV LEDwas tested and analyzed. Onekind of100V AC HV LED、2kinds of100V DC HVLED and one kind of200V HV LED on the basis of50V high-voltage LEDlayoutwere designed and ready to fabricate.(3) The thermal resistance analysis of HV LED wasexplored.The thermalresistance test station was built in the existing conditions of the lab. Thethermalresistance of HV LED coated with phosphor and high-voltage LED without phosphorcoatingare comparedunder the same packaging process conditions. It came to thermalresistance of white LEDcoating with phosphor is17.2℃/W and the thermalresistance of blue high-voltage LED is12.5℃/W. The reason of higher thermalresistance in white LED is probably the white LED is not easy to dissemination theheat because of coating with phosphor, energy losing is in the process of blue-rayexciting phosphors to emit yellow light and the lost energy is converted into heat toincreasing its thermal resistance. While thethermal resistance of1W HV white LEDand1W conventional LED were compared, it is discovered that the thermal resistanceof high-voltage white LED is4.8℃/W higher than general white LED, which isrelatively because numbers ofinterconnection electrodes and the deep trenches.(4) The thermal simulation of local key structure by using finite element analysissoftware ANSYS. The heat distribution on the surface of12V,50V HV LED chipwasanalyzed by using infrared thermal imager. The theory about the different temperature distribution of part areas in the surface of chipwas studied. Finally, it came to theweaknesses in the structure of HV LED chip by carrying out high-current HV LEDimpact test to analysis of the reasons of corruption and combined with data obtainedby infrared testing, which provides a good reference for the subsequent design ofmore reliable HV LED.