Design and Performance Assessment of ZnO Schottky TFT-based Room Temperature Hydrogen Gas Sensor

The concept of a hydrogen (H2) sensor operating at room temperature (RT) based on a zinc oxide (ZnO) Schottky thin-film transistor (TFT) is reported in this work. Owing to its excellent chemical and thermal stability, ZnO is widely employed as a semiconductor material under sensor operating conditions. However, the TFT sensor response at RT requires significant improvement for the advancement of highly precise gas sensors in applications such as space exploration, automotive systems, domestic safety, and environmental monitoring. The sensing capability of the proposed device has been evaluated using palladium (Pd) and gold (Au) as source/drain contacts, leveraging the effective variations in their work functions in response to hydrogen adsorption at the metal surface. The sensor exhibits a minimum detection limit of 250 ppm and a maximum detection limit of 4000 ppm at RT. A detailed concentration-dependent analysis has been performed, focusing on variations in energy band structure, electrostatic potential, transconductance (gm), transient response, and the output and transfer characteristics of the device. Furthermore, the applicability of drain current (ID), channel conductance (gd), threshold voltage (VTH), and sub-threshold slope (SS) as reliable gas-sensing metrics is demonstrated. At 4000 ppm H2 concentration, the optimally engineered sensor achieves ID sensing responses of 341 and 252.16%, gd responses of 58.45 and 19.93%, along with corresponding variations in VTH and SS for Pd- and Au-based devices, respectively, at RT.