High Responsivity Si-Ge Waveguide Avalanche Photodiodes Enhanced by Loop Reflector
Yuan Yuan, Zhihong Huang, Xiaoge Zeng, Di Liang, Wayne V. Sorin, Marco Fiorentino, Raymond G. Beausoleil
Abstract
We present a loop reflector-assisted silicon-germanium waveguide avalanche photodiode with improved responsivity. Compared to the same APD without the reflector, it has 1.49 times higher responsivity, ~ 1.12 A/W, without compromising the speed performance. It exhibits a 3 dB-bandwidth of ~ 25 GHz, a build-up time limited gain-bandwidth product of ~ 296 GHz, a highest gain-bandwidth product of ~ 497 GHz. Clear eye diagrams are measured at both 32 Gbps NRZ and 64 Gbps PAM4 modulation, and a 1 ~ 2 dB better sensitivity up to -15.7 dBm with 32 Gbps NRZ at a BER of 2.4 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> .