Optimization of a-IGZO top gate thin film transistor for ammonia gas sensor

This study introduces an a-IGZO based thin film transistor incorporating catalytic metals as gate contacts, designed for gas sensing applications. The controllability of the channel may be altered by varying the gate electrode's work function, which enhances sensing capabilities. This research explores CO, Mo, Pd, and Ru as gate electrode metals and evaluates OFF current sensitivity by modifying the work function. The OFF-state sensitivity values for Pd, Co, Ru, and Mo, with a work function change of 200 meV, are 7.37, 9.94, 555.56, and 2179.51, respectively. Among them, the Mo gate electrode exhibits outstanding OFF sensitivity, making it highly suitable for NH₃ gas sensing. The author examines dielectric materials ranging from low to high permittivity and identifies HfO₂ as the optimal selection due to its ability to enhance gate capacitance, reduce leakage current, and improve the efficiency of carrier conduction in the channel. The OFF current sensitivity is influenced by the thickness of the channel layer, with reported values of 1418.36, 1899.53, 2119.31, and 2179.51 for thicknesses of 30 nm, 25 nm, 20 nm, and 15 nm, respectively. The work function is studied based on different gas amounts, leading to OFF current sensitivity values of 2.14, 5.59, 68.33, and 2179.51 for gas concentrations of 1, 2, 5, and 9 ppm, respectively. • A novel a-IGZO-based thin film transistor is proposed for NH₃ gas sensing applications. • The optimal channel layer thickness of the a-IGZO material was determined for enhanced device. • The electrical and analog parameter of the device systematically investigated. • OFF-state sensitivity for NH₃ gas measured for Mo as the gate electrode and HfO₂ as the dielectric material.