On Cold Operation of an SiGe HBT as a Broadband Low-NEP THz Direct Detector

This paper reports on cold operation of a SiGe HBT in an experimental $0.13-\mu \mathrm{m}$ technology as a broadband THz power detector and compares it against the classical forward-active operation range based on a frequency-dependent nonlinear device model. In the near-THz fractional bandwidth of 250-1000 GHz, a state-of-the-art optical NEP of 3.9—28 pW/$\surd{HZ}$ and 2.1-16 pW/}$\surd{HZ}$ for cold and forward-active operation, respectively, was measured for the antenna-coupled THz detector comprising 2 devices in common-base (CB) configuration.