Quantum dot (QD) single-electron transistors (SETs), using phosphorous
dopant atom QDs with radii as small as ~1.2 nm, are electrically characterised
down to the ~100 fA level and over a wide temperature range, from room temperature (RT = 300 K) to 8 K. The QDs are embedded within highly-scaled
~5 nm silicon nanochannels. Full ‘Coulomb diamond’, current staircase, single electron characteristics have been measured at 8 K, with low current levels
(~100 fA – 5 pA) and power (35 fW). Single electron addition energies Ea ~
0.3 eV are among the highest reported for dopant atom transistors. Unlike
lithographically defined QDs, the ultra-small size of the QDs implies that both
charging and quantisation energies are large, each ~0.1 eV or greater, and the
current cross-sectional area very small, down to a 4.5 nm2 dopant atom-based
channel. Transitions in conduction from RT – 10 K are characterised using
Arrhenius plots. Current magnitudes reduce by ~106 and activation energies
match Ea, as the device condenses into dopant atom transport channels.