ZERO DIMENSIONAL RESONANT TUNNELING THROUGH SINGLE DONOR STATES

We have observed remarkable new structure in the source-drain I(V) characteristics of a symmetric double barrier resonant tunneling device in which the cross sectional area may be varied from ≅ 1μm2 to ≅0.1 μm2 by applying a voltage to a gate. In the source-drain voltage range close to, but slightly below, the threshold for current flow, peaks are observed with a peak value of ≅ 20 pA, and peak/valley ratio up to 10 1. The structure in I(V) is independent of temperature between 35 mK and 10 K, and of gate voltage between 0 and -2 V. The first peak in I(V) in each polarity is unaffected by a magnetic field applied parallel to the current flow for fields up to 6 T. This structure cannot be explained by lateral quantisation or Coulomb blockade arising from the confinement. We propose that it is due to resonant tunneling between zero-dimensional states formed in the active region by the Coulombic potential of a single ionised donor, combined with the barrier potential. © 1992.