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Implementation of linearly modulated work function AσB1−σ gate electrode and Si0.55Ge0.45 N+ pocket doping for performance improvement in gate stack vertical-TFET

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Abstract

In this work, the characteristics of linearly graded work function (LGW) by utilizing the composition of binary metal alloy AσB1−σ gate electrode and the characteristics of Si-Si0.55Ge0.45 middle N+ pocket heterojunction at the interface of source and channel is explored in the high-k gate stack vertical-TFET (GS-VTFET). The proposed novel structure of VTFET is gradually developed from the single metal gate work function to linearly graded work function of binary metal alloy gate with and without incorporating the Si0.55Ge0.45 N+ pocket and then their various performance parameters of the design are compared. The combined effects of LGW and Si0.55Ge0.45 N+ pocket in GS-VTFET (GS-LGWN-VTFET) show high-performance improvement in subthreshold slope (SS), ON-current (ION), and transconductance generation efficiency (TGE) without affecting the OFF-current (IOFF). GS-LGWN-VTFET renders 5 mV/dec SS, which is 85% lower than the SS of gate stack-single metal work function (GS-SGW-VTFET), and also it exhibits 1 order higher ION keeping the ION/IOFF ratio 1012. Low bandgap Si–Si0.55Ge0.45 N+ causes narrow band-bending and thus results in high tunneling and steeper SS whereas further scaling in SS is possible due to the inclusion of the LGW, which sharps the electrons tunneling rate.

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Wadhwa, G., Singh, J. Implementation of linearly modulated work function AσB1−σ gate electrode and Si0.55Ge0.45 N+ pocket doping for performance improvement in gate stack vertical-TFET. Appl. Phys. A 126, 877 (2020). https://doi.org/10.1007/s00339-020-04065-5

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