Interface-trap effects in inversion-type enhancement-mode InGaAs/ZrO2 n-channel MOSFETs

Interface-trap effects are analyzed in inversion-type enhancement-mode In0.53Ga0.47As/ZrO2 and In0.53Ga0.47As/In0.2Ga0.8As/ZrO2 n-channel MOSFETs bycomparing the measurements and the numerical device simulationsof dc transfer characteristics. Device simulations can reproduce measured threshold voltages under the hypothesis thatinterface traps are donorlike throughout the InGaAs band gap,allowing for strong inversion operation regardless of the relativelyhigh interface-trap density. The effects induced by the donorlikeinterface traps in MOSFETs having a thin In0.2Ga0.8As cap layer interposed between gate dielectric and channel are qualitatively different from those observed in standard MOSFETs (without the cap). Increasing the donorlike trap density decreases the threshold voltage in capped devices, whereas it leaves it unchanged in uncapped ones. As a result, donorlike interface traps can explain the threshold-voltage difference observed in MOSFETs with and without the cap.