研究目的
Investigating the design and characterization of a lens-integrated, THz direct detector based on a global antenna/detector co-design, maximizing the detector’s responsivity for a broadband frequency operation in the 200 GHz to 1 THz band.
研究成果
The detector shows the largest BW with NEP values < 40 pW/√Hz from 220 GHz to 1 THz. In the forward-active bias region with RL = 1.83 k? the detector achieves its best performance, a minimum NEP of around 1.9 pW/√Hz at 292 GHz. Between 275 GHz to 525 GHz the NEP is smaller than 4.3 pW/√Hz. In the saturation region without RL the NEP between 275 GHz to 525 GHz does not exceed 6.3 pW/√Hz with a minimum of 5.1 pW/√Hz at 292 GHz.
研究不足
The antenna is rapidly loosing its radiation efficiency at around 290 GHz. At around 340 GHz the antenna driving impedance is featured by a drop in the real and imaginary parts. There is not much space to enhance the detector performance by further improvements of the antenna design.
1：Experimental Design and Method Selection:
The detector includes a minimum-sized transistor pair, operating in common-base configuration and driven differentially by the antenna. The DC path on the emitter nodes is provided by the antenna ring. The detector is operated in a voltage-mode readout.
2：Sample Selection and Data Sources:
The upper-right off-axis detector located at a 270 μm distance from the chip center is studied.
3：List of Experimental Equipment and Materials:
A 3-mm hyper-hemispherical silicon lens, wire-bonded to a FR4 PCB metalized on the lens side and covered with absorbing material. Three pre-calibrated, antenna-equipped extension modules were used for detector characterization.
4：Experimental Procedures and Operational Workflow:
The assembly was mounted on a motorized 2-D rotational stage in the antenna far-field zone (100 mm distance). The Friis transmission formula was used to determine the input power levels at the lens aperture.
5：Data Analysis Methods:
The voltage noise spectral density (vn) and the voltage responsivity across a chopping frequency were measured with a E4440A spectrum analyzer from Agilent and a Femto HVA-10-M-60-F buffer amplifier. The NEP was calculated as the ratio of spot noise and Rv at the chopping frequency.
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