Transceiver Performance Enhanced Green Micro-LED Based on Pre-Layer Structure Enable Multifunctional Applications in Underwater Visible Light Communication

Underwater visible light (UVLC) system based on a single transceiver-integrated micro-light-emitting diode (mu LED) pixel, especially mu LED devices suitable for this multifunctional application, were rarely reported. This study improved the external quantum efficiency and modulation bandwidth of green mu LEDs by using an InGaN pre-layer to mitigating lattice mismatch and minimizing quantum confined stark effect. Moreover, pre-layer region increased absorbed optical length and the photogenerated carriers in this region were screened from radiation recombination, which significantly increased the responsivity of the mu LED PD when turned on. At 3.9 V bias, remarkable responsivity up to of 0.42 and 0.14 A/W for 405 and 450 nm were obtained, respectively. The increased thickness of the active region also leads to a decrease in the junction capacitance and improves the receiving bandwidth. Based on the transceiver performance improvement, we developed a 1.05 Gbps full-duplex UVLC system with single green mu LED simultaneously acting as receiver and transmitter for the uplink and downlink, respectively. The single mu LED functioned similar to an underwater transceiver antenna. The device achieved a power-conversion efficiency of 14.7% for blue light when used as a photovoltaic cell. Thus, this multifunctional mu LED can facilitate the realization of miniaturized underwater optical antennas with low power consumption and high integration.