Design and analysis of Z shaped InGa0.5As0.5/Si tunnel FET using non-equilibrium Green’s function model for hydrogen gas sensing application

Abstract

—In this paper, a high-k stacked gate Z shaped hetero-juncture TFET (Z-HTFET) is introduced as transducer sensor for the application of hydrogen gas detection. The positioning of stacked gate over the entire source region resulting Z shaped TFET exhibits vertical line tunneling mechanism between the source and the channel yielding higher ON state current (Id) as compared to conventional double gate (DG) TFET. Further, the combination of low band gap source of In0.5Ga0.5As and hetero-gate dielectric engineering helps to facilitate improved device current, steeper subthreshold slope and lower leakage current (Ileak) conduction. Here, palladium (Pd) and the high-k gate stack (HfO2/SiO2) is used as the sensing platform. The induced shift in work function of Pd gate electrode due to the dissociation and diffusion of hydrogen gas molecules into the catalytic gate metal is considered as the detection metric for calculating the sensitivity of the proposed TFET based gas sensor. The behavior of the hydrogen gas sensor is studied using numerical device simulator in terms of surface potential, electric field, transfer characteristics, transconductance, Id/Ileak ratio with variation in work-function and finally Id/Ileak sensitivity is measured. The sensor behavior for a wide range of temperature is also examined to explore the temperature stability of the device. The comparative performance analysis of Z-HTFET with sensitivity of 95.26% establishes the superiority of the device for hydrogen gas sensing as compared to some of the recently reported FET based sensors.