5: Counting electrons with
a single-electron transistor
The current flowing in a single-electron transistor increases with the bias voltage between the source and drain, and varies periodically with the gate voltage. For low bias voltages, current flows when the charge on the gate capacitor is a half-integer multiple of e, but is suppressed for integer multiples of e. Each time an electron is added to the gate, an electron tunnels into the island, which sets the field in the gate capacitor back to its initial value. Peaks in the conductance are observed for half-integer multiples of e, and minima are seen at integer multiples of e. For bias voltages larger than e/C, conduction occurs independently of the gate voltage.