2.5 GHz GaN multiple quantum well micro-photodetector for high-speed visible light communication

This work reported a high-bandwidth GaN multiple quantum wells (MQWs)-based micro-photodetector (PD) with a record modulation bandwidth of 2.5 GHz used as an optical receiver in the visible light communication (VLC) system. We fabricated GaN MQWs-based micro-PDs on the sapphire substrate and investigated the optoelectronic and bandwidth characteristics of the 20 $\upmu$m micro-PD at high reverse biases. The micro-PD has low background noise at high reverse bias voltages and excellent wavelength selectivity. Then, we tested the VLC systems at different reverse biases by using the orthogonal frequency division multiplexing (OFDM) modulation scheme and a bit-loading algorithm. A data rate of 12.7716 Gbps over a 0.3-m free-space link was demonstrated by the micro-PD at a reverse bias voltage of 70 V. Our work experimentally demonstrates that the GaN MQWs-based micro-PD has excellent optoelectronic characteristics and bandwidth characteristics even at high reverse bias voltages, making it a promising device for high-speed VLC receivers.