Dielectric and temperature-dependent optimization of an asymmetric gate-drain engineered core-shell dopingless...

This work presents a comprehensive study of a core-shell Asymmetric Dopingless Nanotube Tunnel Field Effect Transistor (A-DL-NT-TFET), designed to overcome the limitations of conventional TFET architectures. The device employs asymmetric gate design to enhance tunneling, doping-less operation to remove abrupt junctions and ensure uniform control, and a cylindrical nanotube geometry to improve electrostatics while minimizing parasitic effects. 3-D Sentaurus TCAD simulations were used to compare the core-shell A-DL-NT-TFET with its equivalent nanowire (NW) counterpart (A-DL-NW-TFET). The nanotube achieves an ON-state current of 8.49 × 10^-7 A µm^-1, which is approximately 1.43 times higher than that of the nanowire. Moreover, its OFF-state current is suppressed to 5.92 × 10^-21 A µm^-1, nearly 6.1 × 10³ times lower than that of the nanowire (3.61 × 10^-17 A µm^-1). Consequently, the device attains an impressive I _ON/I _OFF ratio of 1.43 × 10¹⁴. Device performance is further analyzed using various gate dielectric materials (air, SiO₂, Al₂O₃, ZrO₂, and HfO₂) and operating temperatures (200-500 K). The results show that high-k dielectrics enhance tunneling efficiency and ON current, while SiO₂ at 300 K offers the best trade-off, sustaining a minimum SS of 57.1 mV dec^-1 alongside favorable OFF leakage and threshold stability. The device exhibits a superior analog and RF performance with a peak transconductance of 1.18 µS and a low output conductance in the 10^-7 S range. It also achieves a cut-off frequency of 24.2 GHz, a GBP of 6.29 GHz, a GFP of 242 GHz, and a THz-class GTFP of 2.38 THz. This establishes the proposed core-shell A-DL-NT-TFET as a strong candidate for ultra-low-power communication systems.