Performance of gate-all-around tunneling field-effect transistors based on Si_1-x Ge_x layer

Electrical performances of gate-all-around (GAA) tunneling field-effect transistors (TFETs) based on a silicon germanium (Si_1-xGe _x) layer have been investigated in terms of subthreshold swing (SS), on/off current ratio, on-state current (I_on). Cut-off frequency (fT) and maximum oscillation frequency (f_max) were demonstrated from smallsignal parameters such as effective gate resistance (R_g), gate-drain capacitance (C_gd), and transconductance (g_m). According to the technology computer-aided design (TCAD) simulation results, the current drivability, fT, and f_max of GAA TFETs based on Si _1-xGe_x layer were higher than those of GAA TFETs based on silicon. The simulated devices had 60 nm channel length and 10 nm channel radius. A GAA TFET with x = 0.4 had maximum I_on of 51.4 μA/μm, maximum fT of 72 GHz, and maximum f_max of 610 GHz. Additionally, improvements of performance at the presented device with PNPN junctions were demonstrated in terms of I_on, SS, fT, and f_max. When the device was designed with x = 0.4 and n+ layer width (W_n) = 6 nm, it shows I_on of 271 μA/μm, fT of 245 GHz, and f_max of 1.49 THz at an operating bias (VGS = VDS = 1.0V).