A Terahertz Detector Array in a SiGe HBT Technology

This paper presents HBT terahertz power detectors implemented in an experimental 0.25- μm SiGe process technology with a peak fT/fmax of 280/435 GHz. Based on the nonlinearity of the HBT base-emitter junction, the detector operates as a square-law down converter, mixing terahertz frequencies directly to dc. Fifteen detectors have been arranged in a 3 × 5-pixel array with differential on-chip ring antennas. The array has been assembled with a hyper-hemispherical silicon lens. Referred to the collecting aperture of the lens, a maximum optical current responsivity R
_I
of 1 A/W and a minimum noise equivalent power (NEP) of about 50 pW/√{Hz} have been measured at 0.7 THz with a 125-kHz chopping frequency. The detectors have been characterized from 0.65 to 1 THz.