title: Slow-light effect in a silicon photonic crystal waveguide as a sub-bandgap photodiode.
abstract: We demonstrate a Si sub-bandgap photodiode in a photonic crystal slow-light waveguide that operates at telecom wavelengths and can be fabricated using a Ge-free, standard Si-photonics CMOS process. In photodiodes based on absorption via mid-bandgap states, the slow-light enhancement enables performance that is well balanced among high responsivity, low dark current, high speed, wide working spectrum, and CMOS-process compatibility, all of which are otherwise difficult to achieve simultaneously. Owing to the slow-light effect and supplemental gain at a high reverse bias, the photodiode shows a responsivity of 0.15  A/W with a low dark current of 40 nA, which is attributed to no particular processes such as ion implantation and excess exposure of the Si surface. The maximum responsivity was 0.36  A/W. The modest gain allows for sufficient frequency bandwidth to observe an eye opening at up to 30  Gb/s.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Terada
authors.forename: Kenji
authors.initials: K
authors.lastname: Miyasaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ito
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Baba