Novel SiGe/Si Heterojunction Double-Gate Tunneling FETs with a Heterogate Dielectric for High Performance

In this paper, a new SiGe/Si heterojunction double-gate heterogate dielectric tunneling field-effect transistor with an auxiliary tunneling barrier layer (HJ-HD-P-DGTFET) is proposed and investigated using TCAD tools. SiGe material has a smaller band gap than Si, so a heterojunction with SiGe(source)/Si(channel) can result in a smaller tunneling distance, which is very helpful in boosting the tunneling rate. The gate dielectric near the drain region consists of low-k SiO₂ to weaken the gate control of the channel-drain tunneling junction and reduce the ambipolar current (I_amb). In contrast, the gate dielectric near the source region consists of high-k HfO₂ to increase the on-state current (I_on) through the method of gate control. To further increase I_on, an n⁺-doped auxiliary tunneling barrier layer (pocket)is used to reduce the tunneling distance. Therefore, the proposed HJ-HD-P-DGTFET can obtain a higher on-state current and suppressed ambipolar effect. The simulation results show that a large I_on of 7.79 × 10^-5 A/μm, a suppressed I_off of 8.16 × 10^-18 A/μm, minimum subthreshold swing (SS_min) of 19 mV/dec, a cutoff frequency (f_T) of 19.95 GHz, and gain bandwidth product (GBW) of 2.07 GHz can be achieved. The data indicate that HJ-HD-P-DGTFET is a promising device for low-power-consumption radio frequency applications.