Effects of Parasitic Source/Drain Junction Area on Terahertz Responsivity of MOSFET Detector

This paper reports the effect of the source/drain junction area on the responsivity of a metal-oxide field-effect transistor (MOSFET)-based terahertz (THz) detector. From the numerical analysis based on the distributed-channel model for the plasma-wave detection mechanism, it is predicted that both the responsivity and noise-equivalent power (NEP) are improved with a relatively larger source junction area than drain junction area. For experimental verification, three types of MOSFET detectors with different source/drain junction areas are fabricated with 65-nm CMOS technology. From on-wafer measurement at 0.3 THz, 2.57 times enhanced responsivity and 63% reduced NEP have been obtained in the sample with the smallest drain junction area and the largest source junction area.