Study and Analysis of the Effects of SiGe Source and Pocket-Doped Channel on Sensing Performance of Dielectrically Modulated Tunnel FET-Based Biosensors

Dielectrically modulated tunnel FET (DMTFET)-based biosensors show higher sensitivity but lower subthreshold current compared with their dielectrically modulated FET counterpart. In this context, the effect of use of silicon-germanium (SiGe) source and n(+)-pocket-doped channel is investigated with the help of extensive device-level simulations. This paper explores the underlying physics of germanium composition variation in the source region, and doping concentration variation in n(+)-pocket region, from the perspective of biomolecule conjugation. The effects of source bandgap and tunneling length over the band-to-band tunneling component have been analyzed, and, subsequently, the sensing performance of DMTFETs has been estimated. The results show that SiGe-source DMTFET has significant superiority over n(+)-pocket DMTFET for attaining higher subthreshold current level while retaining acceptable sensitivity. Such sensitivity-current optimization has been studied for different gate and drain biases, and the suitable biasing range of operation has been indicated. In addition, the relative efficiency of SiGe source and n(+)-pocket-doped channel has been studied under different biomolecule sample specifications. Finally, the influence of trap-assisted tunneling on DMTFET sensing performance has been analyzed, and the comparative role of SiGe source and n(+) pocket has also been indicated in this context.