Deblina Sarkar, Harald Gossner, Walter Hansch, and Kaustav Banerjee. Appl. Phys. Lett. 102, 023110 (2013)

Abstract

A gas-sensor based on tunnel-field-effect-transistor (TFET) is proposed that leverages the unique current injection mechanism in the form of quantum-mechanical band-to-band tunneling to achieve substantially improved performance compared to conventional metal-oxide-semiconductor field-effect-transistors (MOSFETs) for detection of gas species under ambient conditions. While nonlocal phonon-assisted tunneling model is used for detailed device simulations, in order to provide better physical insights, analytical formula for sensitivity is derived for both metal as well as organic conducting polymer based sensing elements. Analytical derivations are also presented for capturing the effects of temperature on sensor performance. Combining the developed analytical and numerical models, intricate properties of the sensor such as gate bias dependence of sensitivity, relationship between the required work-function modulation and subthreshold swing, counter-intuitive increase in threshold voltage for MOSFETs and reduction in tunneling probability for TFETs with temperature are explained. It is shown that TFET gas-sensors can not only lead to more than 10 000× increase in sensitivity but also provide design flexibility and immunity against screening of work-function modulation through non-specific gases as well as ensure stable operation under temperature variations.

Chemical sensors for gases1–7 are not only indispensable for modern society in order to ensure safety, health, and environmental reservation but can also boost fundamental research in areas like physics of thin films and heterogeneous catalysis. Specially, the gas-sensors based on the work-function modulation of the gate of a field-effect-transistor (FET) is highly attractive due to low power consumption, possibility of integration in microsystems, and ability to detect both chemisorbed and weakly bound physisorbed species at room temperature.1 In this letter, a gas sensor is proposed that leverages the band-to-band-tunneling current-injection mechanism of Tunnel-FET8–13 to achieve significantly superior performance under ambient conditions compared to conventional FETs. The results are discussed in terms of two important sensing elements: metal (Pd/Pt) and conducting polymers as the gate material (Fig. 1).