  A scheme of resonant tunneling through the metastable state of semiconductor
quantum dot is presented and implemented in the transport study of freestanding
InAs quantum dots grown on GaAs(001) under illumination using conductive atomic
force microscopy. The metastable state is achieved by capturing one
photoexcited Fermi hole in the valence energy level of InAs quantum dot.
Resonant tunneling through single quantum dot can be observed at room
temperature due to the existence of metastable state. The amplitude of
tunneling current depends on the barrier arrangement and the concentration of
photoexcited holes around the quantum dot, but is found steady when the height
of dot varies from 1.8 to 9.9 nm, which are in good agreement with the proposed
model. The experiment demonstrates a solution of room temperature operated
single electron device to amplify the photocurrent by the singularity of
resonant tunneling in epitaxial quantum dot.
