Design Of Flexible Micro AlGaInP-LED Arrays And Study On Fabrication Technology

As the technology developing and facing urgent requirement of application,the research on light emitting diode(LED)based on inorganic semiconductor trends to become micro,arraying,integrated and flexible.Flexible optoelectronic devices has extended application fields of traditional inorganic optoelectronic devices.As the flexible micro-LED arrays device has the advantages of integration and flexibility,it has attracted many attentions of researchers and many results have been reported.Flexible micro-LED arrays device surmounts mechanical limitation and exhibits high mechanical deformability because of particularly designed structure and suitable fabrication technology,so that it is given the features that high pliability and adhering to arbitrary curved-surfaces or surfaces of irregular bodies.This thesis pays attentions to design flexible micro-LED arrays device based epitaxial AlGaInP-LED wafer and the fabrication technology.The flexible micro-LED arrays device was designed and a sample is fabricated successfully.Furthermore,the issue about heat dissipation in the device was discussed.The works in the thesis are as follow:1.The research on basic theory about inorganic LED.The major issues included basic luminous mechanism,the factors effecting the efficiency and efficiency droop,interior mechanism of current-voltage characters and equivalent circuits;2.After comparing the features of deferent polymer materials,polydimethylsiloxane(PDMS)and polyimide(PI)were chosen as connection and substrate,respectively.The thicknesses of flexible substrate and encapsulating layer were calculated in designed multi-layers structure of flexible micro-LED arrays device,and mechanical features of bending device were analyzed;3.A fan-shaped structure for connecting electrode was designed and optimized,and the reliability and fatigue were discussed.Based that,muti-tracks structure for connecting electrode was presented.Multi-tracks electrode has avoided strain concentrating in some regions and made stress distribution decentralized.Comparing straight or single track electrode,multi-tracks electrode was more stretchable and bendable;4.The fabrication process based on MEMS technology for fabricating flexible micro-AlGaInP-LED arrays device was designed.The technologies that chemical wet-etching,ICP etching,metals deposition,chemically mechanical polishing and others were researched.Grooves with high aspect-ratio,thinning Ga As substrate,connecting electrode and bonding pad arrays were accomplished.Based above results,a sample of flexible AlGaInP-LED micro-arrays device with 8×8 pixels was fabricated;5.The electrical and optical energy loss was analyzed during the electrical-to-optical energy conversion process in LED.Based on the test results of the sample,the factors effecting heat dissipation in flexible micro-arrays were discussed.Thermal conductivity was the primary factor determining the heat dissipation capacity of flexible substrate,and the recommended substrate thickness was determined to be in the 500–1000 ?m range.Larger the center distance of LED pixels could be helpful in weakening heat accumulation,and micro-structured substrates is another promising approach for improving the heat dissipation.