Double-dot charge transport in Si single-electron/hole transistors

We studied transport through ultrasmall Si quantum-dot transistors fabricated from silicon-on-insulator wafers. At high temperatures, 4<T<100 K, the devices show single-electron or single-hole transport through the lithographically defined dot. At T<4 K, current through the devices is characterized by multidot transport. From the analysis of the transport in samples with double-dot characteristics, we conclude that extra dots are formed inside the thermally grown gate oxide which surrounds the lithographically defined dot.