TCAD-Assisted Progress on the Cisco Platform Toward Low-Bias 200 Gbit/s vertical-pin Ge- on-Si Waveguide Photodetectors

We discuss the characterization and numerical simulation of vertical Ge-on-Si waveguide photodetectors (VPIN WPDs) of the Cisco platform for data communications in the O-band (
$1.31 \,\mu \mathrm{m}$
), with the goal of optimizing their frequency response while integrating them into low-power systems. In a large set of WPDs belonging to 6 different structural variants, at a standard bias voltage of
$-2 \,\mathrm{V}$
the best specimens exhibit an intrinsic electro-optic bandwidth of more than
$40 \,\mathrm{G}\mathrm{Hz}$
, which is reduced to about
$10 \,\mathrm{G}\mathrm{Hz}$
at zero bias. A comprehensive 3D multiphysics model, validated through the characterization campaign, provides design guidelines towards intrinsic bandwidths not only wider than
$60 \,\mathrm{G}\mathrm{Hz}$
at
$-2 \,\mathrm{V}$
, directly suitable for application in 200 Gbit/s systems, but also wider than
$40 \,\mathrm{G}\mathrm{Hz}$
at zero bias, not including the possible recourse to extrinsic parameter engineering.