The Impact of Dopant Diffusion on Random Dopant Fluctuation in Si Nanowire FETs: A Quantum Transport Study

In this work, we perform statistical quantum transport simulations with $3\times 3 \mathrm{n}\mathrm{m}^{2}$ Si nanowire (NW) field-effect transistors (FETs) to investigate the impact of dopant diffusion on random dopant fluctuation. First, we use an effective mass Hamiltonian for the transport where the confinement and transport effective masses are extracted from the tight-binding band structure calculations. The dopant diffusion along the transport direction from the source$/$drain regions to the channel region is modeled by the Gaussian doping profile. To generate random discrete dopants, we adopt a rejection scheme considering the 3-dimensional atomic arrangement of the NW structures. Our statistical simulation results show that the diffused dopants into the channel region cause large variability problems in Si NW FETs.