Size-Dependent Characteristics of High-Bandwidth Photodetector Based on GaN Micro-LEDs and LEDs for High-Speed Visible Light Communication
Yue Liao, Xinyi Shan, Zhiwei Rao, Guobin Wang, Runze Lin, Xugao Cui, Ke Xu, Pengfei Tian
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m. We find that the 300 \boldsymbol <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m device has the highest photocurrent when the light incident power of the device is the same, and the 20 \boldsymbol <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> 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- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> 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.