Although single dopant signatures have been observed at low temperature [1-2], the impact on transistor performance of a single dopant atom at room temperature is not yet well understood. Here, for the first time, we provide an in-depth understanding of single dopant influence on NMOSFETs characteristics by linking low and room temperature transport. We demonstrate that, for gate length of 30 nm and below (channel length down to 10 nm), the presence of a single dopant dramatically alters the subthreshold behaviour when the dopant is located in the middle of the channel. Moving the dopants away from the channel leads to enhanced variability above the threshold voltage Vt.
[Show abstract][Hide abstract] ABSTRACT: We have carried out 3D Non-Equilibrium Green Function simulations of a junctionless gate-all-around n-type silicon nanowire transistor of 4.2 × 4.2 nm<sup>2</sup> cross-section. We model the dopants in a fully atomistic way. The dopant distributions are randomly generated following an average doping concentration of 10<sup>20</sup> cm<sup>-3</sup>. Elastic and inelastic Phonon scattering is considered in our simulation. Considering the dopants in a discrete way is the first step in the simulation of random dopant variability in junctionless transistors in a fully quantum mechanical way. Our results show that, for devices with an “unlucky” dopant configuration, with a starvation of donors under the gate, the threshold voltage can increase by a few hundred mV relative to devices with a more homogeneous distribution of dopants.
Ultimate Integration on Silicon (ULIS), 2011 12th International Conference on; 04/2011
[Show abstract][Hide abstract] ABSTRACT: We access properties of single dopants embedded in ultra-scaled MOSFET. In such nanostructures, the ionization energy of a single dopant is enhanced. We establish a new method to determine the energy spectrum of a single dopant by connecting two dopants in series and using one dopant as an energy probe for the second one. Gigahertz microwave driving of this double donor system reveals coherent charge transfert in this ultimate “atomic” transistor.
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