Band-Offset Engineering for GeSn-SiGeSn Hetero Tunnel FETs and the Role of Strain
Open Access
- 12 January 2015
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Journal of the Electron Devices Society
- Vol. 3 (3), 164-175
- https://doi.org/10.1109/jeds.2015.2390971
Abstract
In this paper a simulation study of the effect of conduction and valence band offsets on the subthreshold swing (SS) of a double-gate tunnel field-effect transistor (TFET) with gate-overlapped source is presented. The simulations show that if the pn-junction and the hetero-junction coincide, the band offsets can significantly improve the SS by suppressing the so-called point tunneling at the pn-junction. It turns out that the performance of an n-channel TFET is determined by the direct conduction band offset whereas that of a p-channel TFET is mainly effected by the energy difference between the light hole bands of the two materials. Thus, the performance of the hetero-junction TFET can be improved by selecting material systems with high conduction or valence band offsets. The misalignment between the pn-junction and the hetero-junction is shown to degrade the SS. The above-described band-offset engineering has been applied to the GeSn/SiGeSn hetero-structure system with and without strain. Simulations of GeSn/SiGeSn hetero-TFETs with band-to-band-tunneling parameters determined from pseudopotential calculations show that compressive strain in GeSn widens the design space for TFET application while tensile strain reduces it.Funding Information
- European Community’s Seventh Frame-Work Programme (619509)
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