Design of a High-Speed PIN Photodiode With a Gradually-Doped Composite Absorption Layer for 100 Gbit/s Optical Receivers

In this paper, we propose a high-speed PIN photodiode with a composite absorption layer. It supports a 3-dB bandwidth of 43 GHz and can be used in 100 Gbit/s optical receivers. The composite absorption layer consists of a gradually-doped p-type absorption layer and an undoped absorption layer. It has different carrier transport mechanisms from the traditional PIN-PD with a single intrinsic absorption layer. The gradually-doped p-type absorption layer accelerates electron diffusion in the p-type absorption layer. Comparison of three kinds of PIN photodiodes with different absorption layers shows that the proposed PIN-PD provides the highest bandwidth while ensuring satisfactory responsivity. The simulation used a numerical model, calculated by Crosslight APSYS software. The results were compared with the analytical method and obtained a good agreement. This work offers a novel structure and good guidance for the design and optimization of photodiodes.