Multiscale modeling of silicon-nanowire-based Schottoky barrier FETs for the biosensor applications
D. Nozaki, F. Zörgiebel, J. Kunstmann , W. M. Weber, G. Cuniberti
Approximate Quantum-Methods: Advances, Challenges and Perspectives
2010.9.20-24; Bremen Center for Computational Materials Science
Over the last few decades, 1D semiconducting silicon-nanowires (SiNWs) have been widely investigated as potential building blocks for future electronic devices because of their excellent electrical performance compared with bulk silicon, small sizes, and controllable bottom-up fabrications . Many groups have demonstrated promising biosensor applications of SiNW-based field effect transistors (FETs) . Recently Weber et al. have reported dopant-free Shottky barrier (SB) FETs consisting of intrinsic SiNWs working as a channel and NiSi2 nanowires working as source and drain contacts with gate lengths down to sub-photolithographic values . Measurements of their transport characteristics have shown the highest on-current and on-conductance values recorded to date for intrinsic SiNW-FETs . These SiNW-based SB-FETs are also expected to provide promising platforms for biosensor applications. In this work, we have developed a multi-scaled theoretical framework for the study of biosensors consisting of the intrinsic SiNW-based SB-FETs and biomolecules (receptors) covering the surface of the SiNWs. The aim of our study is to investigate the changes in the current through the SB-FETs in response to the binding of the ligands to the bio-receptors attached on the surface of the SiNWs. For this purpose, we have combined two approaches in different scales: one is a classical 1D-tunneling problem at the Si/NiSi2 interfaces in SB-FETs and another is the calculation of the electrostatic perturbation due to the biomolecules (receptors) attached on the surface of the NWs in atomistic scale using density functional theory. As a first step, in order to understand the basic charge transport characteristics though the SiNWs, we have modeled pristine SiNW-based SB-FETs consisting of an intrinsic SiNW working as a channel and NiSi2 NWs working as source and drain without the biomolecules. We have calculated the electrostatic potential profiles across the Si/NiSi2 interfaces with different gate lengths and gate voltages. Then we analyzed the influence of the gate lengths and the gate voltages on the charge tunneling through the SB-FETs. In addition, we have analyzed how the length dependence of the conductance in the SiNW-SB-FETs relates with the Anderson localization regime .
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