Full-duplex visible light communication system based on single blue mini-LED acting as transmitter and photodetector simultaneously

Abstract

GaN-based light emitting diodes (LEDs) have potential as photodetectors (PDs) for visible light communication (VLC). In current studies on LED-based PDs, devices are operated in a reverse-biased or zero-biased state. In this work, the performance of an 80 × 120 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> blue mini-LED as both a PD and light source was studied. An aluminum oxide passivation was deposited on the sidewalls of the active region using atomic-layer deposition. In addition to improving the external quantum efficiency of mini-LEDs and reducing leakage current, sidewall passivation can also increase the responsivity of mini-LED PD. At the injection current used for display, the mini-LED device still worked as a PD with a good response to illumination. At a bias of 3 V (corresponding to injection current of 11.5 mA), the mini-LED PD had a response of 0.243 A/W and a high on-off ratio of 1.33 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> . A cascaded bridged-T amplitude equalizer was used to extend the OE −3 dB bandwidth of mini-LED PD from 16 MHz to 116 MHz at 3V bias. Based on the system above, a VLC link over 1 m with a data rate of 528 Mbps is achieved using 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing. Moreover, the mini-LED PD could simultaneously act as an uplink detector and a downlink transmitter in the same full-duplex VLC system. With transmission distance of 1m/ 1m, a transmission rate of 350 Mbps in the uplink and downlink was achieved. With transmission distance increasing to 1.2 m/1.2 m and 1.5 m/1.5 m, full-duplex VLC systems are also capable of achieving transmission rates of 300 Mbps and 225 Mbps, respectively. The proposed method allows the same mini-LED to be used simultaneously as a display and VLC transmitter and receiver, which not only simplifies the structure of the full-duplex communication system and reduces system power consumption, but also facilitates the integration of multifunctional small LED devices.