Hetero-gate dielectric SiGe/Si tunnel FET: a hydrogen gas sensor with improved sensitivity

A new p-type Si0.6Ge0.4/Si TFET transducer sensor with hetero-gate dielectric engineering (HGD-SiGe-TFET) is proposed. The combination of low bandgap source Si0.6Ge0.4 and high-k dielectric HfO2 adjacent to the tunneling junction improves the ON current significantly. Further, the presence of silicon in both the channel and drain limits the rise of leakage current and ambipolarity, respectively. Thus, the simulated HGD-SiGe-TFET provides a maximum I-ON/I-AMB current ratio of 1.29 x 10(6) with optimized HfO2 length. The Palladium gate metal (Pd) along with the HfO2-SiO2 gate dielectric has been used as a sensing platform. The sensing process relies on the principle of measuring the induced shift of work function of the Pd metal gate with variation in the gas pressure. The current sensitivity and subthreshold swing (SS) sensitivity of the proposed sensor for different hydrogen gas pressure has been investigated extensively. The sensor behavior for a wide range of temperatures and drain bias is also examined. The proposed sensor exhibits superior sensitivity in terms of drain current and average SS compared to conventional TFET-based sensors. The design also seems fairly stable over a broad range of temperatures with negligible sensitivity variation. The successful implementation of the HGD-SiGe-TFET as a hydrogen gas sensor may lead to new developments in nanostructure gas sensing applications.