High-sensitivity ammonia gas sensors based on source pocket double-gate vertical hetero-junction TFETs

Abstract This article introduces a novel ammonia (NH 3 ) gas sensor utilizing a highly doped SiGe source pocket double-gate vertical heterojunction tunnel field transistor (SP-DG-VHJ-TFET) and examines its sensitivity when paired with Molybdenum (Mo) as the gate metal. The use of Mo offers superior work function, enhanced chemical stability, and improved adhesion which results in better gate control, reduced leakage currents, and improved device performance compared to traditional TFETs. The vertical arrangement of the source, channel, and drain will bolster the device’s stability. The addition of a highly doped SiGe layer between the source-channel interface reduces the tunnelling barrier, improves carrier injection, and enhances tunnelling efficiency, and results in better device performance and sensitivity, particularly for ammonia gas detection. The variations in the pocket parameters like pocket length, height, width and pocket doping etc are analysed concerning the adsorption of gas molecules using the Silvaco ATLAS TCAD. The SP-DG-VHJ-TFET with a 50 nm gate length exhibits outstanding sensitivity (S Id(ON) ∼ 4.5 × 10 −1 ) and an impressive I ON /I OFF ratio (∼1.3 × 10 10 ) when Mo is used as the gate metal.