Probing a single dopant in ultra-scaled CMOS transistors
Tuesday 26 January 2010 at 4pm
CNRS Bât E, conference room "Louis Weil" on 3rd floor
Xavier Jehl (INAC, SPSMS, CEA Grenoble)
We use the microelectronics technology to fabricate silicon transistors channels with a very small volume, i.e. short, narrow and thin (10x50x20 nm). Low temperature spectroscopy of such devices reveals the characteristics of single dopants which have diffused from the highly-doped source and drain to the channel below the gate [1].
We observe direct electronic transport through a single arsenic dopant, and extract its ionization energy. This energy is about twice the ideal value calculated for a bulk Si host crystal. This is due to the so-called 'dielectric confinement effect', arising from materials with a different dielectric constant than Si very close to the dopant, and was calculated recently for a nanowire geometry [2]. Our measurements also shed light on the large sample-to-sample variability observed at 300K as it is due to thermally broadened transport through these dopant states.
[1] M. Pierre et al., Nature Nanotechnology, published online 6 dec. 2009[2] M. Diarra et al., Phys. Rev. B75, 045301 (2007).
