Symmetric Operation in an Extended Back Gate JLFET for Scaling to the 5-nm Regime Considering Quantum Confinement Effects

Abstract

In this paper, we propose a double gate junctionless FET (DGJLFET) with an extended back gate (EBG) architecture for significantly improved performance in the sub-10-nm regime. Even for a channel length of 5 nm, we show using calibrated 2-D simulations that the EBG DGJLFET, when compared with the DGJLFET, exhibits: 1) an improved subthreshold swing; 2) a significantly low off-state leakage current; and 3) a considerably high $I_{\mathrm{\scriptscriptstyle ON}}/I_{{\mathrm{\scriptscriptstyle OFF}}}$ ratio of $\sim 10^{8}$ . Furthermore, we demonstrate, for the first time, that the quantum confinement-induced bandgap widening diminishes the parasitic bipolar junction transistor (BJT) action and, therefore, facilitates the scaling of the conventional DGJLFETs to the sub-5-nm channel regime where the quantization effects are significant. Moreover, we also show, for the first time, that the DG junctionless accumulation mode FET suffers from an enhanced parasitic BJT action and, therefore, a significantly high off-state leakage current compared with the DGJLFET. In addition, we demonstrate that the loss of gate control for negative gate voltages in the DGJLFETs with larger silicon film doping ( $N_{D} \geq 2 \times 10^{19}$ cm $^{-3}$ ) is due to a shielding effect initiated by the band-to-band tunneling.