Fabrication Of GaN-based Micro-LED Arrays

With the development of visible light communication technology and the increasingly higher requirements for the application of LED chip lighting and communication performance,the emergence of micro-LEDs array satisfies the above requirements and has become a research hotspot.Compared with traditional LED chips,GaN-based micro-LEDs array have better electrical and optical performance,and have many advantages such as high brightness,high resolution,low cost and corresponding speed,which are very promising technologies.In this thesis,the structure optimization,preparation and package process of GaN-based micro-LEDs array were studied to achieve excellent photoelectric properties and high modulation bandwidth.Firstly,we designed the layout and fabrication process of 4×4 micro-LEDs array.The process optimization of the ITO film that determines the lateral current expansion capability was performed.It was found that the sheet resistance was 41.5?/?and the blue light band transmittance was as high as 96%after annealing at 550°C for 3 minutes..The step-by-step baking etching method is used to deal with the problem of side corrosion that often occurs in the wet etching of ITO,and the problems of unclean ITO corrosion and side corrosion were solved.The effects of different chip sizes and electrode sizes on the photoelectric properties of the chip were compared.When the diameter of the micro-size chip was 60?m,the diameter of the original plate electrode was 20?m,the saturation current density can reach6363.2 A/cm~2.At the same time,the luminous flux,luminous efficiency and modulation bandwidth characteristics of the packaged 4×4 micro-sized array chip were analyzed.When the chip size is 60?m,the saturated luminous flux is 7.5 lm,the light efficiency was 144.3lm/W,which is equivalent current density of 350 mA injection to 45 mil×45 mil chip(26.79A/cm~2),and the modulation bandwidth of 123.3 Mhz was obtained with a current injection of60 mA.Subsequently,the thick photoresist process,low-damage plasma etching and damage repair technology in the deep etching process are optimized to complete the preparation of the deep isolation trench.The pixels are separated into mutually independent light units that do not interfere with each other,and are filled with insulating materials and vapor-deposited electrodes cross-link the pixels into a whole to make 8×8 micro-LEDs array.The effects of different etching depths and different electrode lead lengths on the photoelectric properties of the chips in the array were studied.Further comparing the maximum saturation current densities of the corresponding cells in the 4×4 array and the 8×8 array shows that as the density of the array chips increases.Analysis of luminous flux,luminous efficiency and modulation bandwidth of the packaged 8×8 micro-size array chips,more attention should be paid to the heat dissipation ability of the device to enhance the stability of the device.Finally,in order to further improve the light output power and efficiency of the chip,a 1×N series and parallel high-power LED array structure is designed and prepared,and the effects of series and parallel structures on chip voltage,luminous power,luminous efficiency and peak wavelength are compared in detail.The analysis of the luminous flux,luminous efficiency and modulation bandwidth characteristics of the 1×N micro-size array chip shows that the series structure can effectively increase the overall luminous flux in the guarantee of the modulation bandwidth,indicating that the micro-size array LED device has great potential in visible light communication applications.