Steep Switching Characteristics of L-Shaped Tunnel FET With Doping Engineering

Abstract

In this work, a L-shaped tunnel FET (TFET), which has the dominant tunneling current in the normal direction to the gate, is introduced with the doping engineering and its electrical characteristics are analyzed using TCAD device simulations. The proposed L-shaped TFET has the pocket doping (p+-doping for n-type operations) underlying the gate, which can suppress the corner tunneling generated near the source edge by the electric-field crowding. Thus, the on/off transition is significantly improved since the corner tunneling is the main cause of the degradation of the switching characteristics. To maximize the performance enhancement, the concentration of the pocket doping ( ${N} _{\mathrm {POC}}$ ) is optimized. As a result, the averaged subthreshold swing ( $SS_{\mathrm {AVE}}$ ) gets reduced from 60 to 26 mV/dec and the on-current ( ${I} _{\mathrm {ON}}$ ) becomes ~ 2.0 times increased as compared to the conventional L-shaped TFETs. Moreover, it is confirmed that the pocket doping effectively suppresses the corner tunneling without the on-current reduction even in the extremely scaled gate length ( ${L} _{\mathrm {G}}$ ) device.

Keywords

• Band-to-band tunneling (BTBT)
• gate-normal tunnel FET (TFET)
• L-shaped TFET
• corner tunneling
• subthreshold swing (SS)
• hump phenomenon