A Lens-Coupled On-Chip Antenna for Dual-Polarization SiGe HBT THz Direct Detector

In this letter, a silicon lens-coupled dual-polarization on-chip ring antenna for THz direct detection in 0.13  $\mu$ m SiGe heterojunction bipolar transistor (HBT) technology is presented. In particular, various circuit-antenna co-design aspects are addressed, including the detector frequency-dependent driving impedance and responsivity, and the necessity of accommodating multiple dc signal lines in the antenna layout. Due to an adequate circuit/electromagnetic (EM) modeling approach, close-to-optimum detector operation in a near-THz fractional bandwidth with consistent radiation patterns up to 1 THz and state-of-the-art peak optical responsivity of 3.1 A/W around 400–500 GHz among silicon direct detectors could be demonstrated.