Stacked quantum dot transistor and charge- induced confinement enhancement

As the size of a transistor continuously scales down, single electron effects become important [1 – 3]. Previously, we have studied charge transport in single-electron quantum dot transistors which have a channel consisting of a silicon dot separated from the source and the drain by two constrictions [4], and in single-electron MOS memories that have a polysilicon dot floating gate stacked on a straight channel [3]. In this Letter, we propose and demonstrate a novel stacked quantum dot transistor (QDT) that has a polysilicon dot floating gate stacked on top of a silicon dot channel, and report how transport through the silicon dot channel can be affected by the charges stored in the floating dot gate. We have observed that the peak-tovalley ratio and the peak separation of the conductance were enhanced after charging the electrons into the floating gate. This effect is explained as a result of the enhanced charge confinement in the silicon quantum dot channel.