On the other hand, little or weak correlations between I d and the number of As dopants are found. The weak positive correlations with N s NU7026 research buy and N at the off-state are attributed to a tendency that a larger number of dopants lead to smaller L g *. In order to further investigate the effect of the number of As, I d-V g characteristics

of NWs implanted at a smaller dose of 2 × 1014 cm−2 were calculated. The average number of active As atoms in this NW is 16, which averages 1.8 × 1020 cm−3. The average and standard deviation of the on-current in this NW are almost the same as those in the 1 × 1015 cm−2 NW. This is consistent with little or weak correlations between I d and the number of As dopants as we mentioned above. However, a few out of 100 NW devices of 2 × 1014 JQ-EZ-05 ic50 cm−2 have on-current which is only about one half its average. This is attributable to the large interatomic distances of discrete As atoms in these devices. These results indicate that the on-current fluctuation

is caused by the fluctuation of interatomic distances of discrete As atoms, not by the fluctuation of the number of As. The off-current fluctuation can be reduced by a process in which dopants in the S/D extensions are likely to exist near the channel region. In contrast, the on-current fluctuation may be inherent in ultra-small NW transistors because interatomic distance is determined by random atomic movement. Conclusions We have theoretically investigated the effects of random discrete distribution of implanted and annealed As atoms in the S/D extensions on the device characteristics of n-type GAA Si NW transistors. KMC simulation is used for generating realistic random distribution of active As atoms in Si NWs, and the current–voltage characteristics are calculated using the oxyclozanide NEGF method. The fluctuation of drain current

is observed with the normalized standard deviation of approximately 0.2. The correlation between the drain current and the factors related to random As distribution is examined. The results indicate that the on-current fluctuation is not directly due to the fluctuation of the number of dopants in the S/D extensions. The on-current fluctuation may be caused by the randomness of As dopant positions in the S/D extensions and hence is inherent in ultra-small NW transistors. Acknowledgments We acknowledge Dr. Ignacio Martin Bragado for the fruitful discussions on KMC modeling. References 1. Roy S, Asenov A: Where do the dopants go? Science 2005, 309:388–390. 2. Martinez A, Aldegunde M, Seoane N, Brown AR, Barker JR, Asenov A: Quantum-transport study on the impact of channel length and cross sections on variability induced by random discrete dopants in narrow gate-all-around silicon nanowire transistors. Electron Devices, IEEE Transactions 2011, 58:2209–2217.CrossRef 3. Wang X, Brown AR, Cheng B, Asenov A: Statistical variability and reliability in nanoscale FinFETs.