Low-current transport through dopant atom-based quantum dots in a nanoscale silicon transistor

Quantum dot (QD) single-electron transistors, using phosphorous dopant atom QDs with radii as small as ∼1.2 nm, are electrically characterized 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 to 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 quantization energies are large, each ∼0.1 eV or greater, and the current cross-sectional area is very small, down to a 4.5 nm2 dopant atom-based channel. Transitions in conduction from RT to 10 K are characterized using Arrhenius plots. Current magnitudes reduce by ∼106, and activation energies match Ea, as the device condenses into dopant atom transport channels.