High Responsivity Si-Ge Waveguide Avalanche Photodiodes Enhanced by Loop Reflector

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, <inline-formula><tex-math notation= LaTeX >$\\sim$</tex-math></inline-formula>1.12\xa0A/W, without compromising the speed performance. It exhibits a 3 dB-bandwidth of <inline-formula><tex-math notation= LaTeX >$\\sim$</tex-math></inline-formula>25\xa0GHz, a build-up time limited gain-bandwidth product of <inline-formula><tex-math notation= LaTeX >$\\sim$</tex-math></inline-formula>296\xa0GHz, a highest gain-bandwidth product of <inline-formula><tex-math notation= LaTeX >$\\sim$</tex-math></inline-formula>497\xa0GHz. Clear eye diagrams are measured at both 32\xa0Gbps NRZ and 64\xa0Gbps PAM4 modulation, and a 1 <inline-formula><tex-math notation= LaTeX >$\\sim$</tex-math></inline-formula> 2\xa0dB better sensitivity up to −15.7\xa0dBm with 32\xa0Gbps NRZ at a BER of 2.4 <inline-formula><tex-math notation= LaTeX >$\\times 10^{-4}$</tex-math></inline-formula>.