# Improvement of Electrical Performance in Heterostructure Junctions TFET Based on Dual Material Gate
## 2 Methods  
Figure 1a shows the device structure of conventional JLTFET, in which the PG is located at the source region and has a larger work function than CG for inducing a P+ source while CG is located at the middle for inducing intrinsic channel, and a heavily doping is considered in silicon body with concentration of \(1\times 10^{19}\) cm\({}^{-3}\), resulting in a junctionless P\({}^{+}\)-N\({}^{+}\)-I-N\({}^{+}\) structure with appropriate workfunctions for PG and CG by charge plasma concept. Compared with conventional JLTFET, the difference of heterostructure junctionless tunnel field-effect transistor (HJLTFET) is that ON-state current can be improved by heterojunction at source/channel interface, as shown in Figure 1b. Based on conventional HJLTFET, DMMG-HJLTFET still uses Si/SiGe heterostructure at the source/channel interface and introduces a sandwich stack structure (GaAs/Si/GaAs) at drain region to suppress OFF-state current and ambipolar current, moreover, the gate electrode is divided into three parts namely auxiliary gate (M1), control gate (M2), and tunnel gate (M3) with workfunctions \(\Phi_{\text{M1}}\), \(\Phi_{\text{M2}}\) and \(\Phi_{\text{M3}}\), respectively, where \(\Phi_{\text{M1}}=\Phi_{\text{M3}}<\Phi_{\text{M2}}\), as shown in Figure 1c. As a result, the DMMG-HJLTFET has a larger ON-state current and lower OFF-state current than JLTFET and HJLTFET, so it is possible  
to be applied to low power integrated circuit. Table 1 shows the fundamental geometrical parameters of the different devices.  
All the simulations are carried out in Silvaco Atlas 5.20.2.R [32; 33; 34; 35]. The nonlocal BTBT model (BBT.NONLOCAL) is used to take into account the spatial variation of the energy bands and the nonlocal generation of electrons and holes. Because of the presence of highly doped channel, Shockley-Read-Hall related to concentration (CONSRH) is used for accounting the minority carrier recombination effects, at the same time, Fermi Statistics (FERMI) and band gap narrowing (BGN) model are also activated to reduce the carrier concentration in the simulation. Moreover, quantum confinement effects due to the increased doping levels and thinner gate oxide in the channel distinctly influence the device  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter Name** & **JLTFET** & **HJLTFET** & **DMMG-HJLTFET** \\ \hline Length of source (L\({}_{\text{S}}\)/nm) & 20 & 20 & 20 \\ Length of channel (L\({}_{\text{CH}}\)/nm) & 20 & 20 & 20 \\ Length of drain (L\({}_{\text{D}}\)/nm) & 20 & 20 & 20 \\ Length of gap (L\({}_{\text{SG}}\)/nm) & 5 & 5 & 5 \\ Thickness of SiO2 and HfO2(T\({}_{\text{OX}}\)/nm) & 2 & 2 & 2 \\ Thickness of the silicon body (Tsi/nm) & 5 & 5 & 5 \\ Thickness of the Si (Ts/nm) in sandwich stack & 3 & 3 & 3 \\ Length of auxiliary gate(L1/nm) & & & 7 \\ Length of control gate(L2/nm) & & & 10 \\ Length of tunnel gate(L3/nm) & & & 3 \\ Work function of polarity gate(\(\Phi_{\text{PC}}\)/eV) & 5.9 & 5.9 & 5.9 \\ Work function of control gate(\(\Phi_{\text{CC}}\)/eV) & 4.6 & 4.6 & 4.6 \\ Work function of auxiliary gate(\(\Phi_{\text{MI}}\)/eV) & & & 4.1 \\ Work function of tunnel gate(\(\Phi_{\text{M}}\)/eV) & & & 4.1 \\ N-type doping concentration (N\({}_{\text{C}}\)/cm\({}^{-3}\)) & \(1\times 10^{19}\) & \(1\times 10^{19}\) & \(1\times 10^{19}\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: The fundamental geometrical parameters of the different devices.  
Figure 1: Cross-sectional view of **(a)** JLTFET; **(b)** HJLTFET; **(c)** DMMG-HJLTFET.  
characteristics, so quantum confinement model given by [PERSON] (HANSCHQM) is also considered in our simulation. Furthermore, tunneling of electrons from the valence band to the conduction band through trap or defect states and phonon assisted tunneling effects of indirect band gap semiconductors can have an important effect on the current, in order to involve these effects, the [PERSON] model for trap Assisted tunneling (SCHENK.TUNN) and band to band tunneling model given by [PERSON] (SCHENK.BBT) are also included.