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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N} _{\mathrm {POC}}$ </tex-math></inline-formula> ) is optimized. As a result, the averaged subthreshold swing ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$SS_{\mathrm {AVE}}$ </tex-math></inline-formula> ) gets reduced from 60 to 26 mV/dec and the on-current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\mathrm {ON}}$ </tex-math></inline-formula> ) 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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\mathrm {G}}$ </tex-math></inline-formula> ) device.
Highlights
For digital applications, the low power operation is one of the big concerns as Internet of Things (IoT) and wearable technology is quickly developing to improve our quality of life [1]–[3]
The experimental transfer characteristics of the previously reported L-shaped tunnel FET (TFET) are reproduced with the Band-to-band tunneling (BTBT) model for the simulation accuracy as shown in Fig. 2 [23]
It is observed that the SSAVE and VON are hardly degraded by the LG scaling-down, meaning that the proposed L-shaped TFET is robust against short-channel effects (SCEs)
Summary
The low power operation is one of the big concerns as Internet of Things (IoT) and wearable technology is quickly developing to improve our quality of life [1]–[3]. As a breakthrough, the steep switching devices such as tunnel FET (TFET) and negative capacitance FET (NCFET) have been widely studied [6]–[15]. The TFETs with tunneling in the normal direction to a gate by using the epichannel region (gate-normal TFET) has been widely researched to be competitive with conventional CMOS performance [16]– [20]. The L-shaped TFET with the doping engineering is proposed to achieve steep switching characteristics. The process integration flow of the proposed L-shaped TFET is demonstrated in terms of the fabrication feasibility
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