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A high performance triple-heterojunction (3HJ) design has been previously proposed for tunneling FETs (TFETs). Compared with single HJ TFETs, the 3HJ TFETs have both shorter tunneling distance and two transmission resonances that significantly improve the ON-state current ( I\scriptscriptstyle {\text {ON}} ). Coherent quantum transport simulation predicts that I\scriptscriptstyle {\text {ON}} = 460~\mu \textsf {A}/\mu \textsf {m} can be achieved at gate length \text Lg = 15~\textsf nm , supply voltage V\textsf {DD} = 0.3~\textsf V , and OFF-state current I\scriptscriptstyle {\text {OFF}} = 1~\textsf {nA}/\mu \textsf {m} . However, strong electron–phonon and electron–electron scattering in the heavily doped leads implies that the 3HJ devices operate far from the ideal coherent limit. In this paper, such scattering effects are assessed by a newly developed multiscale transport model, which combines the ballistic nonequilibrium Green’s function method for the channel and the drift-diffusion scattering method for the leads. Simulation results show that the thermalizing scattering in the leads both degrades the 3HJ TFET’s subthreshold swing through scattering-induced leakage and reduces the turn-ON current through the access resistance. Assuming bulk scattering rates and carrier mobilities, the I\scriptscriptstyle {\text {ON}} is dropped from 460~\mu \textsf A/\mu \textsf m down to 254~\mu \textsf A/\mu \textsf m , which is still much larger than the single HJ TFET case. [ABSTRACT FROM AUTHOR]

GaSb/InAs heterojunction tunnel FETs are strong candidates in building future low-power ICs, as they could provide both steep subthreshold swing and large ON-state current ( I\mathrm{\scriptscriptstyle ON} ). However, at short-channel lengths, they suffer from large tunneling leakage originating from the small bandgap and small effective masses of the InAs channel. As proposed in this paper, this problem can be significantly mitigated by reducing the channel thickness, meanwhile retaining a thick source-channel tunnel junction, thus forming a design with a nonuniform body thickness. Because of the quantum confinement, the thin InAs channel offers a large bandgap and large effective masses, reducing the ambipolar and source-to-drain tunneling leakage at OFF-state. The thick GaSb/InAs tunnel junction, instead, offers a low tunnel barrier and small effective masses, allowing a large tunnel probability at ON-state. In addition, the confinement-induced band discontinuity enhances the tunnel electric field and creates a resonant state, further improving I\mathrm{\scriptscriptstyle ON} . Atomistic quantum transport simulations show that ballistic I\mathrm{\scriptscriptstyle ON}=284 A/m is obtained at 15-nm channel length, I\mathrm{\scriptscriptstyle OFF}=1\times 10^{-3} A/m, and V\mathrm{DD}=0.3 V, while with uniform body thickness, the largest achievable I\mathrm{\scriptscriptstyle ON} is only 25 A/m. Simulations also indicate that this design is scalable to sub-10-nm channel length. [ABSTRACT FROM AUTHOR]

We describe the design of double-gate InAs/GaSb tunneling field-effect transistors (TFETs) using GaSb electron wave reflector(s) in the InAs channel. The reflections from the source p-n junction and from the reflector(s) add destructively, causing the net transmission to approach unity at certain energies. The energy range of transmission enhancement can be broadened by the appropriate placement of multiple barriers. With 10^ -3 A/m \mathrm\scriptstyle OFF -current ( I\mathrm{\scriptscriptstyle OFF}) and a 0.3 V power supply, the subthreshold swing is improved from 14.4 to 4.6 mV/decade and the ON-current ( I\mathrm{\scriptscriptstyle ON}) is improved from 35 to 96 A/m, compared with a conventional GaSb/InAs TFET. [ABSTRACT FROM PUBLISHER]