Impact of subthreshold slope on sensitivity of square law detector for high frequency radio wave detection

An impact of subthreshold slope on sensitivity of square law detectors composed of an FET has been investigated. Theoretical consideration starting from the unified charge control model of FET channel carriers comes down to formulae which indicate that the subthreshold slope significantly affects output voltage and sensitivity of the square law detector. Experiments carried out to detect gigahertz waves using a MOSFET which has a body terminal isolated from other terminals and, therefore, is able to operate as the dynamic threshold voltage MOSFET show the significance of the subthreshold slope. Verification performed by detecting terahertz waves using HEMT detectors also proves the theoretical conclusion and almost agrees with detection characteristics predicted from derived mathematical formulae.