Design Optimization of L-Shaped Gate Negative Capacitance Si/Ge Heterojunction TFET With Channel Doping

In this paper, to improve the performance of L-shaped gate heterojunction tunneling field-effect transistor (LG-HJ-TFET), an L-shaped gate negative capacitance Si/Ge heterojunction TFET with channel doping (NCHJCD-LTFET) was proposed, whose electrical characteristics were investigated through technology computer-aided design simulations in Sentaurus. The NCHJ-CD-LTFET has doping (nsup+/sup-doping for an n-type TFET) in the corner region of the channel, which plays an important role in modulating the energy bands that reduce the bandgap between the source and channel in the doping area. Thus, compared with the LG-HJ-TFET, the band-to-band tunneling of NCHJ-CD-LTFET occurs at a lower gate voltage (VsubGS/sub), and the threshold voltage (VsubTH/sub) is significantly reduced from 0.221 to 0.181 V. In addition, a ferroelectric layer was deposited above the horizontal gate dielectric to further improve the electrical characteristics owing to the negative-capacitance effects.With comprehensive adjustment the doping concentration of the channel corner region (NsubCH,CO/sub) and the thickness of the ferroelectric layer (TsubFE/sub), the NCHJ-CD-LTFET had a low VsubTH/sub of 0.145 V, a high on-state current (IsubON/sub) of 27.5 μA/μm, a high switching current ratio (IsubON/sub/IsubOFF/sub) of 2.1×10sup8/sup and a steep average subthreshold slope (SSsubAVE/sub) of 24.92 mV/decade.