  2D transition metal dichalcogenides (TMDs) have attracted a lot of attention
recently for energy-efficient tunneling-field-effect transistor (TFET)
applications due to their excellent gate control resulting from their
atomically thin dimensions. However, most TMDs have bandgaps (Eg) and effective
masses (m*) outside the optimum range needed for high performance. It is shown
here that the newly discovered 2D material, few-layer phosphorene, has several
properties ideally suited for TFET applications: 1) direct Eg in the optimum
range ~1.0-0.4 eV, 2) light transport m* (0.15m0), 3) anisotropic m* which
increases the density of states near the band edges, and 4) a high mobility.
These properties combine to provide phosphorene TFET outstanding ION 1 mA/um,
ON/OFF ratio~1e6, scalability to 6 nm channel length and 0.2 V supply voltage,
thereby significantly outperforming the best TMD-TFETs in energy-delay
products. Full-band atomistic quantum transport simulations establish
phosphorene TFETs as serious candidates for energy-eficient and scalable
replacements of MOSFETs.
