Study on the Influence of LED PN Junction Area on Modulation Bandwidth in Visible Light Communication

In recent years, many researchers take great interest on visible light communication (VLC), due to its rich spectrum resources, no electromagnetic interference, good confidentiality, etc. In the visible light communication system, the information is loaded into the LED, then the light is transmitted in the free space, and the detector receives the signal. As the result of the -3dB modulation bandwidth of power-type LED is only several MHz, which affects seriously the information capacity and transmission. Therefore, the enhancement of the modulation bandwidth of LED is major task for VLC. In this paper, based on our previous work, the LED chip with different PN junction area of 200 mu mx800 mu m, 300 mu mx900 mu m and 300 mu mx1200 mu m are designed and fabricated. By analyzing the photoelectric characteristics and modulation characteristics of the three groups of LED, the relationship between PN junction area and modulation bandwidth are showed. Then the influence factors and the enhancement method of modulation bandwidth of power-type LED are proposed.