Static Non-Linearity Based Analysis of Non-Resonant MOSFET as THz Detector
The non-resonant THz response of CMOS FET has been analyzed based on static non-linearities of the transistor channel. Under the quasi-static limit, the second order non-linearities dominantly determine the DC current in the channel generated in response to THz signal. For the applied gate-to source and drain-to-source signals, the significance of the second order non-linear terms is analyzed as a function of DC bias conditions. Based on the analysis, it has also been shown that a differential detector topology can give highest responsivity in cold operation. A tradeoff between the channel resistance and load impedance plays a vital role in detecting the generated current. Moreover, the design considerations such as readout modes, optimum bias points and device dimensions are also discussed with respect to both responsivity and noise equivalent power (NEP).