High sensitivity GaN-based MQWs photodetectors for high-speed visible light communication under weak signals

Although commercial Si-based photodetectors have been widely developed and are highly mature for weak-light detection, GaN photodetectors with multiple quantum wells (MQWs) structures still demonstrate remarkable advantages in weak visible-light sensing due to their inherent spectral selectivity, low dark current, and high reliability. These features make them particularly suitable for challenging scenarios such as long-distance transmission, underwater environments, and rainfall conditions. To investigate their potential for weak-light detection, high-responsivity GaN-based MQWs PDs were fabricated and implemented in VLC systems under challenging environments. Under a -20 V bias and 66.4 mW of 405 nm laser irradiation, a peak photocurrent of 7.23 mA was observed. Responsivities of 1.24 A/W and 1.15 A/W were obtained under biases of -20 V and -5 V, respectively. Initially, a 20 m free-space communication scenario was simulated, yielding a maximum data rate of 5.74 Gbps. Subsequently, a 3.38 m rain environment was constructed with simulated light, moderate and heavy rain conditions, where maximum data rates of 7.77 Gbps, 6.11 Gbps, and 6.03 Gbps were achieved, respectively. Finally, underwater optical communication was evaluated in a 3.38-m-long water tank, resulting in a maximum data rate of 6.57 Gbps. These experimental results indicate significant potential for high-response current GaN-based MQWs PDs in enabling high-speed, multi-scenario optical communication networks.