GaN-based Micro-LED Chips For Visible Light Communication

The LED-based Visible light communication(VLC)technology is expected to alleviate the shortage of global wireless spectrum resources.However,the communication capabilities of general commercial LED devices for lighting are poor.In order to improve the communication performance of the VLC system,the signal source needs to be optimized.The micro-size LED chip can reduce the device capacitance and the RC time,improve the maximum saturation current density of devices and reduce the lifetime of carriers,so that the maximum modulation bandwidth of the VLC system can be increased;a micro-size LED array can not only maintain a large modulation bandwidth,but also increase the maximum data transmission rate and light-output power(LOP)of the chip.Therefore,the size effects and the topological structure of Ga N-based LED array chips are studied in this paper.Based on the theory of VLC,this article analyzes the factors that affect the performance of the VLC,and builds measuring platforms for communication performance of LED chips on wafer or packaged LED devices.The top-emitting LEDs were fabricated at first.The results show that the smaller size of LED chip,the larger 3-d B modulation bandwidth.For a micro-size LED chip with a radius of 30?m,the saturation current density can reach 6000A/cm~2,and the modulation bandwidth can be up to 300 MHz.For micro-size LED parallel array,the results show that the array chip can increase LOP significantly and has the same3-d B modulation bandwidths under the same injected current densities.When the injected current density is 1000 A/cm~2,the LOP of eight-pixels parallel array chip is 6.64 times that of a single-pixel chip.In addition,in the current-ageing experiment of white LED devices,as compared with the large saturation injected current of 130 m A,the small injection current of20 m A leads to an improved lifetime(the enhancement is 93.5 times).Further,flip-chip micro-size LED chips and array chips with DBR mirrors are designed and fabricated.Compared with normal large-size LED chip,the micro-size LED chip has smaller device capacitance and larger modulation bandwidth,thus it is more suitable for VLC;compared with the top-emitting LED,under the same current density,the flip-chip LED has a lower forward voltage and a higher LOP.Finally,the circuit model of the micro-size LED parallel array is analyzed,which shows that the LED parallel array is a high current device while the series array chip is a high voltage device.Moreover,when the injected current densities are the same,the modulation bandwidths of the array chip and single-pixel chip are almost the same,but the maximum data transmission rate of the array chips based VLC system is significantly improved compared to the single-pixel chip(the enhancement is34.6%).