Size-Dependent Characteristics of High-Bandwidth Photodetector Based on GaN Micro-LEDs and LEDs for High-Speed Visible Light Communication

The optimal photodetector (PD) size is an important topic in realizing high-speed VLC systems, but there is still a lack of sufficient research. In this work, we studied the size-dependent characteristics of GaN micro-LED/LED-based PDs. We first tested the photocurrent and bandwidth characteristics of eight different sizes of PDs, including 20, 40, 60, 80, 100, 150, 200, and 300 \boldsymbol $\mu$ m. We find that the 300 \boldsymbol $\mu$ m device has the highest photocurrent when the light incident power of the device is the same, and the 20 \boldsymbol $\mu$ m device has the highest bandwidth of 166.8 MHz. To take into account the effects of bandwidth and photocurrent on VLC, we studied the size-dependent VLC performance of micro-LED/LED-based PDs by using the OFDM scheme. An 80- $\mu$ m micro-LED-based PD has the potential to balance the photocurrent and bandwidth to achieve the highest data rate of 7.1291 Gbps. Our work has proved that the optimal size of micro-LED-based PD is 80 \boldsymbol $\mu$ m which will guide the design of micro-LED/LED-based PD. Furthermore, our micro-LED-based PD array has the potential to be used in multiple-input multiple-output (MIMO) VLC, with a potential data rate up beyond tens of Gbps, which opens a new way to achieve ultra-high-speed communication.