Gate-Modulated Temperature-Dependent NO₂ Gas Responsivity of h-BN Bottom-Gated MoS₂ Field-Effect Transistor

Although many studies have explored 2D material-based field-effect transistor (FET)-type gas sensors to overcome relatively low gas responsivity, the role of gate bias remains unclear and understudied. In this work, the influence of gate-modulated channel states and thermally excited carriers on the responsivity of MoS 2 /h-BN FETs to NO 2 gas is systematically investigated and a detailed mechanism is proposed. The electrical state of the channel is defined through electrical parameters such as threshold voltage, carrier density, and interface trap density, and the corresponding gas responsivity is evaluated using time-domain gas measurements. When the device operates in the subthreshold region, partial channel depletion leads to a weak conduction channel at the surface, where the gas reaction primarily occurs. With increasing temperature, thermally excited carriers further contribute to the gas reaction, resulting in a significant increase in responsivity, up to 2922%, without the need for surface functionalization. This study provides valuable insights into the gas sensing mechanisms of transition metal dichalcogenides-based FETs and proposes effective strategies for enhancing gas response under various conditions.