Band-to-band tunneling field-effect transistors (TFETs) [1][2][3][4][5][6][7] have emerged as promising candidates to replace conventional metal-oxide-semiconductor field-effect transistors (MOSFETs) for lowpower integration circuits and have been demonstrated to overcome the thermionic limit, that results intrinsically in subthreshold swings of at least 60 mV/dec at room temperature 1,5,6 . Here we demonstrate TFETs based on few-layer black phosphorus, in which multiple top gates create electrostatic doping in the source and drain regions. By electrically tuning the doping types and levels in the source and drain regions, the device can be reconfigured to allow for TFET or MOSFET operation and can be tuned to be n-type or p-type. Full band atomistic quantum transport simulations of the fabricated devices agree quantitatively with the I-V measurements which gives credibility to the promising simulation results of ultra-scaled phosphorene TFETs 8,9 . Using atomistic simulations, we project substantial improvements in the performance of the fabricated TFETs when channel thicknesses and oxide thicknesses are scaled down.In recent years, two-dimensional (2D) semiconducting materials have attracted attention as channel material for next-generation transistors [10][11][12][13][14][15] , as the ultra-thin body allows for ideal * Correspondence and requests for materials should be addressed to J.A.

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* (0.15 m0), 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 ~ 106 for a 15 nm channel and 0.5 V supply voltage, thereby significantly outperforming the best TMD-TFETs and CMOS in many aspects such as ON/OFF current ratio and energy-delay products. Furthermore, phosphorene TFETS can scale down to 6 nm channel length and 0.2 V supply voltage within acceptable range in deterioration of the performance metrics. Full-band atomistic quantum transport simulations establish phosphorene TFETs as serious candidates for energy-efficient and scalable replacements of MOSFETs.

The dielectric engineered tunnel field-effect transistor (DE-TFET) as a high performance steep transistor is proposed. In this device, a combination of high-k and low-k dielectrics results in a high electric field at the tunnel junction. As a result a record ON-current of about 1000 uA/um and a subthreshold swing (SS) below 20mV/dec are predicted for WTe2 DE-TFET. The proposed TFET works based on a homojunction channel and electrically doped contacts both of which are immune to interface states, dopant fluctuations, and dopant states in the band gap which typically deteriorate the OFF-state performance and SS in conventional TFETs.Comment: 3 pages, 3 figure

Scaling transistors’ dimensions has been the thrust for the semiconductor industry in the last four decades. However, scaling channel lengths beyond 10 nm has become exceptionally challenging due to the direct tunneling between source and drain which degrades gate control, switching functionality, and worsens power dissipation. Fortunately, the emergence of novel classes of materials with exotic properties in recent times has opened up new avenues in device design. Here, we show that by using channel materials with an anisotropic effective mass, the channel can be scaled down to 1 nm and still provide an excellent switching performance in phosphorene nanoribbon MOSFETs. To solve power consumption challenge besides dimension scaling in conventional transistors, a novel tunnel transistor is proposed which takes advantage of anisotropic mass in both ON- and OFF-state of the operation. Full-band atomistic quantum transport simulations of phosphorene nanoribbon MOSFETs and TFETs based on the new design have been performed as a proof.

Thickness engineered tunneling field-effect transistors (TE-TFET) as a high performance ultra-scaled steep transistor is proposed. This device exploits a specific property of 2D materials: layer thickness dependent energy bandgaps (Eg). Unlike the conventional hetero-junction TFETs, TE-TFET uses spatially varying layer thickness to form a hetero-junction. This offers advantages by avoiding the lattice mismatch problems at the interface. Furthermore, it boosts the ON-current to 1280µA/µm with 15nm channel length. Providing higher ON currents, phosphorene TE-TFET outperforms the homojunction phosphorene and the TMD TFETs in terms of extrinsic energydelay product. TE-TFET also scales well to 9nm with constant field scaling E = VDD/L ch = 33mV /nm. In this work, the operation principles of TE-TFET and its performance sensitivity to the design parameters are investigated through full-band atomistic quantum transport simulations.