OBSERVATION OF SINGLE ELECTRON-HOLE RECOMBINATION AND PHOTON-PUMPED CURRENT IN AN ASYMMETRIC SI SINGLE-ELECTRON TRANSISTOR

We observed a novel type of photocurrent by investigating Coulomb bloc kade oscillations around the few-electron regime in an asymmetric Si s ingle-electron transistor. Photoexcitation generates new current peaks below the threshold voltage only for one polarity of source-drain vol tage. Under low excitation, such photocurrent exhibits intermittent be havior with sudden drops and rises. The phenomena can be ascribed to t he interplay of photogenerated holes and single-electron tunneling via the island. The sudden drop is a manifestation of single-electron rec ombination with a hole in the island.