Key Technologies For Enhancing The Efficiency And Reliability Of LED

The high power semiconductor light emitting diode(LED)is regarded as a new solid-state light source,which has been widely used in many fields,such as green intelligent lighting,visible light communication and so on.With the development of LED,it puts high requirements for its high light efficiency and stability.In this paper,the key techonologies on enhancing the light efficiency and effective thermal management of LED are studied.Improving the LED light efficiency includes improving the internal and external quantum efficiency,among which,the methods to improve the external quantum efficiency mainly include surface roughness and photonic crystal technology.In this paper,the optical proximity effect based lithography process is proposed,and the layered roughing on LED surface is realized by using appropriate fabrication conditions.The Finel near field diffraction theory model of this structure is established,and the optical field distribution of LED surface caused by optical proximity effect is simulated and analyzed.The experiment scheme of layered roughing GaP on AlGaInP LED surface is designed,and experimental study using lithography and reactive ion etching parameters with different effects on the roughing degree of GaP surface layer are investigated,and the light extraction efficiency of the LED is experimentally improved by 162%.Then,in order to further study the effect of the photonic crystal structure on the LED pumping efficiency,the structure of the 2D hexagonal funnel-shape air hole photonic crystal(PC)LED is proposed and the structure parameters are analyzed and optimized.The method based on three beam laser interference ablation(LIA)to pattern GaN LED surface with PC structures is proposed,the effect of laser power and beam angle on laser three beam interference patterns is analyzed.The LIA system is developed,and the relationship between the different laser output power densities and the photonic crystal morphology are explored,and the optimum technological parameters are obtained.The funnel-shape PC GaN LED efficiency is improved by 55.7%compared with that of the flat LED.For the purpose of improving the light efficiency of the LED by improving the internal quantum efficiency of the LED,the effect of Ag/Si HMMs in nano period on the internal quantum efficiency and the response time of the LED are studied.The numerical analysis model of the structure is established,and the effect of the HMMs structure on the LED GaP light efficiency and Purcell coefficient is studied.An experimental method for the fabrication of Ag/Si HMMs GaP structure on the surface of LED is proposed.The Ag/Si HMMs film is fabricated by magnetron sputtering on the surface of GaP,and the focused ion beam etching is used to etch flat HMMs into nano periodic structure.The results show that the light efficiency of GaP LED HMMs with 220nm period is 1 time more than that of the planar LED,and the photon decay rate is increased by 2 times.Lastly,the thermal management of LED is studied,a high power LED thermal management method based on the temperature measurement with a loop feedback conrol is proposed,and the LED heat conduction model is established.the temperature distribution of high power devices LED(CSM 360)with and without heat dissipation device are analyzed respectively with ANSYS,and structures of integrated semiconductor and integrated heat pipe are designed for effective heat dissipation respectively.A constant current driver for CSM 360 with heat pipe based thermal management system is developed to ensure the stability of high power LED.