System integration and packaging of a terahertz photodetector at $ W $-band

This paper presents the system integration and packaging of a photodetector at $W$ -band (75–110 GHz) for terahertz (THz) communications. The ErAs:In(Al)GaAs photoconductor and its feeding network based on semi-insulating indium phosphide (InP) substrate are introduced. The design of the bias tee at $W$ -band is described, and the effect of parasitic modes is discussed. Besides, the transition using the $E$ -plane probe between a $W$ -band rectangular waveguide (WR-10) and a coplanar waveguide (CPW) is illustrated. The bias tee and the $E$ -plane probe transition are based on high-resistivity silicon (Si) substrate where wire bonding bridges are added on the top following the CPWs in order to restrict parasitic modes. The integration approach and the packaging structure are addressed. The proposed bias tee and the $E$ -plane probe transition, including the WR-10 rectangular waveguide, are fabricated, integrated, and measured. The measurement is carried out on-wafer in a back-to-back configuration, and the results are presented. The assembly of the fully packaged photodetector is demonstrated, and a THz heterodyne communication system is implemented, which validates the proposed system integration and packaging approach of the photodetector at $W$ -band.