Design and Performance of High-Speed Avalanche Photodiodes for 100-Gb/s Systems and Beyond

This paper reviews our work on high-speed avalanche photodiodes (APDs) with a unique vertical-illumination structure, targeting 100-Gb/s systems and beyond. The APDs feature easy lateral and vertical scaling for achieving the required operation speed and responsivity. For 100-Gb/s systems, a 3-dB bandwidth of 18.5 GHz with multiplied responsivity of 9.1 A/W is obtained. For larger capacity applications such as 400-Gb/s systems, a maximum 3-dB bandwidth of over 35 GHz and responsivity at a gain of unity of almost 0.7 A/W are obtained by reducing diameter of an n-contact mesa and optimizing thickness and configuration of an absorption layer.