The tunnel field-effect transistor (TFET), which utilises the band-to-band tunnelling mechanism for current conduction, provides the ability to achieve extremely low subthreshold swing ( < 60 mV/dec) and very low off current, thus offering a performance advantage over conventional inversion-mode metal-oxide-semiconductor
field effect transistors (MOSFETs) for the ultra-low power and ultra-low voltage operation for the next generation of transistors. In particular, the optimisation of the TFET architecture and material composition is very important because the full potential of the TFET is not yet uncovered. In this work homo- and heterostructure nanowire TFETs, based on Si, Ge and SiGe materials, have been investigated using device simulation,
for the design of source and drain doping profiles, with nanowire diameters down to 5 nm.