Vertical single electron transistors with separate gates

We demonstrate independent gate action in a vertical sub-micron single electron transistor with four separate gates fabricated by a new technology from a double barrier structure starting material. When the gate voltage is swept over a given range, the number of conductance oscillations increases systematically as the number of gates "squeezing" the quantum dot is varied from one to four. Alternatively, the average period of the conductance oscillations is essentially independent of the number of "squeezing" gates if the gate voltage is appropriately scaled to an "effective gate voltage". We show that subtle changes occur in the appearance of the conductance oscillations when the lateral geometry of the quantum dot is controllably deformed.