4: Principle of the
SET transistor
Like a MOSFET, the single-electron tunnelling (SET) transistor consists of a gate electrode that electrostatically influences electrons travelling between the source and drain electrodes. However, the electrons in the SET transistor need to cross two tunnel junctions that form an isolated conducting electrode called the island. Electrons passing through the island charge and discharge it, and the relative energies of systems containing 0 or 1 extra electrons depends on the gate voltage. At a low sourcedrain voltage, a current will only flow through the SET transistor if these two charge configurations have the same energy.