Abstract
The responsivity of AlGaN/GaN high-electron mobility transistors (HEMTs) when operating as zero-bias RF detectors in the subthreshold regime exhibits different behaviors depending on the operating temperature and gate length of the transistors. We have characterized in temperature (8–400 K) the detection performance of HEMTs with different gate lengths (75–250 nm). The detection results at 1 GHz can be reproduced by a quasi-static model, which allows us to interpret them by inspection of the output − curves of the transistors. We explain the different behaviors observed in terms of the presence or absence of a shift in the zero-current operating point originating from the existence of the gate-leakage current jointly with temperature effects related to the ionization of bulk traps.
Highlights
Academic Editors: Maris Bauer andField-effect transistors (FETs), thanks to their intrinsic nonlinearities, exhibit competitive performance as detectors of RF and THz signals [1]
Different FET technologies have been explored to this end: Si CMOS, graphene FETs, high-electron mobility transistors (HEMTs) based on GaN, GaAs, InGaAs, InAs, etc. [1,2,3,4,5,6,7,8,9,10,11]
Even if the results reported here are specific to GaN HEMTs, a Received: 11 January 2022
Summary
Field-effect transistors (FETs), thanks to their intrinsic nonlinearities, exhibit competitive performance as detectors of RF and THz signals [1]. A decrease in β similar to that of ZVDs takes place [1,11], whereas in others, a saturation at the maximum value achieved around the threshold voltage is observed [6,7,10] Attempts to explain these behaviors as due to the influence of gate-leakage current [4] or detector loading conditions [2,5] have been reported, but a comprehensive physical explanation is still lacking. The same rectification mechanism still holds above the cut-off frequency of the devices as long as it is the result of distributed mixing, when the channel of the FET can no longer be treated as a lumped element, but rather as an ultra-high-frequency waveguide [15,16] This is the frequency range typically addressed in the literature of FET-based detectors, where our conclusions can be directly applicable. It is not the case when entering into the THz range, where thermoelectric or plasmonic effects are involved in the rectification [17,18], and are not directly related to the DC characteristics of the devices
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