Single-dopant spectroscopy and sub-threshold channels at the corners of triple-gate FinFETs

The authors experimentally investigate the microscopic transport characteristics of triple-gated field-effect transistors fabricated in silicon. FinFETs are three dimensional nano-scale devices consisting of a lithographically defined Si nanowire surrounded by a gate and have an active region as small as 50 60 35nm³. Analysis of the low-temperature transport properties of these devices with strong mesoscopic effects makes it possible to experimentally quantify the formation of sub-threshold inversion channels at the edges of the nanowire. By measuring the thermionic as well resonant tunneling current a channel cross-section as small as 4nm² was found. The strong confinement of the current at the edges actually enables us to study resonant transport through single dopants present inside these channels. The charge, orbital and spin properties of the impurity states are determined and their excited states are revealed by means of transport spectroscopy.