Terahertz Imaging Using Strained-Si MODFETs as Sensors

Abstract

Development of new terahertz (THz) direct sensors based on the oscillation of the plasma waves in the channel of sub-micron FETs is increasing in interest due to its great potential in imaging and spectroscopy. FETs based in the heterosystem Si/SiGe is wafer-compatible with mainstream CMOS closely follow both noise and gain performances of III-V families in microwave applications; the high-values of the electron channel mobility make of Si/SiGe transistors potential contenders in the design of new THz detectors. In this contribution we present an experimental study of the sub-THz photoresponse of n-channel Si/SiGe MODFETS with gate lengths of 50nm, gate widths of 30m and source-to-drain distance of 2m. It was found a relative intense response with a maximum around the threshold voltage that can explained as non-resonant detection. Additionally, the transistor was used as a single-pixel sensor in a THz imaging system using a Gunn diode at 0.292 THz as the source. The excellent response of strain-Si transistors in THz image detection at room temperature points out the potential of such transistors for future cost effective and compact THz imaging systems.