Design of a 250-Gbit/s SiGe HBT Electrooptic Modulator

We present a rigorous electrical and optical analysis of a highly scaled, graded-base, SiGe heterojunction bipolar transistor (HBT) electrooptic (EO) modulator. In this study, we propose a 2-D electrical model and a 3-D optical model for a graded-base SiGe HBT structure that is capable of operating at a data bit rate of 250 Gbit/s or higher. In this structure, apart from a polysilicon/low doped emitter
$( \hbox{width} = 90\ \hbox{nm})$
and a strained SiGe graded base
$( \hbox{depth} = 8.5\ \hbox{nm})$
, a selectively implanted collector (SIC)
$(\hbox{depth} = 26\ \hbox{nm})$
is introduced. Furthermore, at a base-emitter swing of 0 to 1.0 V, this model predicts a rise time of 3.48 ps and a fall time of 0.55 ps. Optical simulations predict a
$\pi$
phase shift length
$(L_{\pi})$
of 204
$\mu \hbox{m}$
, with an extinction ratio of 13.2 dB at a wavelength of 1.55
$\mu\hbox{m}$
.