Impact of SiGe on source engineering with different shape tunnel FET structures for gas sensing applications

Abstract

Gas sensing requires highly sensitive and selective sensor technologies for environmentalmonitoring, industrial safety, and public health objectives. Although conventional MOSFET-basedgas sensors are widely utilized, their detection of low quantities of gases, such as ammonia, ishindered by a number of severe constraints. Poor selectivity and restricted sensitivity are two ofthese drawbacks. Tunnel field-effect transistors (TFETs), have emerged as a viable solution forthese problems due to their enhanced electrical characteristics and potential for higher sensitivityin gas sensing applications. Despite its advantages, TFETs have certain disadvantages. The twomain ones are low on-current (ION) and ambipolarity, which can reduce their overall efficiency.Many strategies, including source engineering, shape engineering, channel engineering, and gatedielectric modifications, have been proposed to tackle these issues. This thesis focuses onemploying source engineering (SiGe-pocket at source side) and shape engineering (different TFETshape structure) techniques to improve the performance of TFETs, specifically for ammonia gasdetection. By improving the SiGe-pocket TFET structures and utilizing a novel U-shape structure,the work aims to boost crucial performance metrics such ION, ON/OFF current ratio, total currentdensity, and threshold voltage. Comprehensive simulations on SILVACO TCAD and an analysiscomparing the recommended SiGe-pocket U-shape TFET structure to SiGe-pocket DGTFET,SiGe-pocket vertical TFET, and SiGe-pocket Z-shape TFET designs demonstrate its superiorperformance. Significant improvements in efficiency and sensitivity are obtained by adjusting thework function of the molybdenum (4.40-4.60 eV) catalytic gate metal to find the optimalconfiguration. The findings reveal that the SiGe-pocket U-shape TFET structure exhibits superiorperformance, demonstrating an ION of 8.01??10-4 A/??m, an ON/OFF ratio of 1.25??1013, a totalcurrent density of 1.06??107 A/??m2, and an OFF current sensitivity (SOFF) of 1.262. These resultshighlight the enhanced sensitivity and efficacy of the proposed SiGe-pocket U-shape tunnel FETin ammonia gas sensing applications, making it a promising candidate for practical uses inenvironmental monitoring and industrial safety