Digital Performance Assessment of the Dual-Material Gate GaAs/InAs/Ge Junctionless TFET

In this article, a device called GaAs/InAs/Ge junctionless tunnel field-effect transistor (JL-TFET) is proposed and investigated by a numerical simulator. This device utilizes an InAs pocket at the source side and its digital performance parameters such as subthreshold slope (SS) and ON-state current to OFF-state current (I-ON/IOFF) ratio have been improved in comparison with GaAs/Ge JL-TFET. Simulation results show that the electron tunneling mechanism is based on intraband tunneling and interband tunneling in GaAs/InAs/Ge JL-TFET, while the electron tunneling mechanism is interband tunneling in regular JL-TFET. To further reduce SS, we have proposed for the first time GaAs/InAs/Ge JL-TFET structure with a fixed gate (f-gate), the so-called dual-material gate (DMG) GaAs/InAs/Ge JL-TFET. The f-gate induces a local dip in the conduction band edge leading to more abrupt band bending at the vicinity of the InAs/GaAs interface. Simulation results show that DMG GaAs/InAs/Ge JL-TFET is turned on at lower V-GS compared to GaAs/InAs/Ge JL-TFET, causing a SS is improved. A brief examination of the proposed device has been done on the impacts of both the variations of the f-gate work-function (phi(F)) and the f-gate length (Lf-gate). The DMG GaAs/InAs/Ge JL-TFET with a channel length of 20 nm, phi(F) = 3.7 eV, and Lf-gate = 5 nm showed the average SS of SS = 2.1 mV/dec, and ON-state current of I-ON = 0.51 mA/um. The SS and I-ON of the DMG GaAs/InAs/Ge device are improved by 150% and 76%, respectively, compared to the GaAs/Ge JL-TFET device with similar dimensions. The DMG GaAs/InAs/Ge JL-TFET device proposed in this article can be a reasonable candidate for digital applications.