Ge Photodiode with -3 dB OE Bandwidth of 110 GHz for PIC and ePIC Platforms

Abstract

We present an SOI-waveguide coupled germanium photodiode with very high OE -3 dB bandwidth of ≥110 GHz at reverse bias of 2 V. This performance is achieved by a novel construction in that the germanium is sandwiched in between two in-situ doped silicon regions. This fabrication approach allows for avoiding ion-implantation into the germanium, which is certainly beneficial for the bandwidth as minority carrier diffusion effects are strongly suppressed. A responsivity of >0.6 A/W at 1550 nm (-2 V) is achieved, while the dark current of this device yields to about 300 nA (-2 V). To our knowledge, this is the most advanced germanium photo detector in terms of bandwidth combined with state-of-the-art responsivity as well as moderate dark currents. We demonstrate that the novel photodiodes can be fabricated with high yield.