Bandwidth optimization of GaN-MQW photodetectors for visible light communication via deep etching and bias voltage control

In pursuit of an all-in-one chip for simultaneously working as a transmitter and a receiver of visible light communication (VLC) system, there has been a surge in research that employs GaN multiple quantum well (MQW) epitaxial structures as a photodetector (PD) but a lack of comprehensive research of the bandwidth of GaN-MQW PD. In this paper, we investigated the effects of deep etching and shallow etching processes, as well as bias voltage, on the bandwidth of the PD. The results show that the deep etching process significantly reduces the device capacitance to a minimum of 0.294 pF, thereby removing the limitations of the RC effect on the bandwidth. Meanwhile, without the constraints of the RC effect, the bandwidth increases exponentially with the increase in bias voltage, without significantly reducing the signal-to-noise ratio of the system. Under the conditions of deep etching and high bias voltage, a record-breaking-level bandwidth of 914.475 MHz and a high communication data rate of 12.615 Gbps are achieved. This study guides the analysis and enhancement of the bandwidth for GaN-MQW PDs and validates the tremendous potential of GaN-MQW PDs as receivers for VLC systems.