The Radio Frequency Single-Electron Transistor and the Horizon Picture for Tunneling

Abstract: The main part of this thesis concerns the development of a new type of single electron transistor (SET) called the radio frequency single electron transistor (RF-SET). The RF-SET is the most sensitive electrometer demonstrated. Furthermore, it is the most sensitive voltage amplifier for high impedance sources at high frequencies, thanks to a very small input capacitance. A high bandwidth is obtained by measuring the damping of a microwave resonance circuit. The RF-SET can operate at frequencies approaching the 1/(2.pi. RC) intrinsic limit of the SET. Moreover, it is shown that a quantum limited RF-SET can be fabricated with standard techniques and realizable device parameters. The principle of operation, and the optimized choice of parameters are described. Finally, possible future applications for the RF-SET are discussed.

The second part of this thesis shows that the effect of the electromagnetic environment on Coulomb blockade devices can be estimated through a simple horizon model, in which the interaction length is determined by the Heisenberg uncertainty principle. The advantage of this horizon model can be demonstrated in a device with two tunnel junctions in parallel in which a cut-off voltage related to physical dimensions is observed. This model also explains the characteristics of single junctions and single electron transistors. Moreover, it gives a method for determining the capacitance of an SET.

Finally, the shot noise from high impedance arrays of tunnel junctions are measured. As predicted, the array exhibits a shot noise of reduced Schottky value 2eI/N, where N is the number of junctions in the array.