Versatile Germanium Photodiodes with 3dB Bandwidths from 110 GHz to 265 GHz

Abstract

We demonstrate waveguide coupled germanium fin p-i-n photodiode being on a par with state-of-the-art III-V devices. The intrinsic, undoped germanium regions of the photodiodes are sandwiched in between two complementary in situ-doped silicon regions, circumventing ion-implantation into Ge. By scaling the width of the germanium, different combinations of bandwidths and responsivities can be obtained. Optoelectrical 3-dB bandwidths reaching up to 265 GHz at (1550 nm) 1 mA photocurrent and 2 V reverse bias are shown for a device with ~100 nm narrow germanium fin. Certainly, broader germanium region will yield higher responsivities but on the expense of 3-dB bandwidths. Increase of the germanium width from 100 nm to 450 nm results in a change in internal responsivity from 0.3 A/W to 1 A/W at -2 V bias. The impact of high photocurrent on performance of our new photodiodes will be presented in this paper.