Why FETs detect a THz signal at a frequency far beyond their amplifying capabilities

Abstract

Field-effect transistors (FETs) are efficient detectors of THz radiation. Despite over three decades of research, controversy still exists regarding the detection mechanism. The article attempts to solve this problem systemically. Existing approaches to modeling THz detection are critically reviewed, including plasmonic, resistive mixing, hot carrier and thermal models. Limitations and inconsistencies of the first two approaches, along with some classical physics principles and experiments conducted, were identified. These include the facts that some models were formulated independently of material relaxation time constraints, and the plasmonic approach does not take into account the conditions for the formation of surface plasmon-polarons and does not describe the case of p-type devices (hole plasmons have never been experimentally recorded). Relevant measurements and theoretical considerations illustrate the inadequacy of these models. As a result of this analysis, thermoelectric models are expected to explain THz sensing by FETs.