Noise Properties of the Single Electron Transistor

Doctoral thesis, 2008

The Single Electron Transistor (SET) is a sensitive electrometer with a charge sensitivity ultimately limited by noise. In this thesis we present measurements of noise properties and charge sensitivity of the radio-frequency Single Electron Transistor. The charge sensitivity for the radio frequency Single Electron Transistor (rf-SET) was measured, as a function of different parameters. The demonstrated result is better than the previously best reported sensitivity value both at 40 mK, and at 4.2K. The charge sensitivity at 40mK is 0.9μe/√Hz, 5 times worse than theoretical limit. The charge sensitivity at 4.2K is 1.8 μe/√Hz, only 1.6 times worse then the theoretical limit for this temperature. The limiting factor is the amplifier noise but shot/thermal noise starts to be important. The SET was operated in the radio frequency mode which allowed to measure the low frequency noise of the SET in a wide frequency range from few Hz up to tenths MHz. Noise spectra were measured over a wide range of the gate voltage and bias voltage. In the data analysis we are able to separate noise contributions from different noise sources in the SET. From the low frequency noise measurements, we conclude that the noise spectrum in the frequency range (f > 10 kHz) is dominated by electron capture and emission kinetics on a electrostatic trap most probably consisting of a metallic grains outside the tunnel barrier. We have also introduced a method of direct measurement of the shot noise in the SET in low-frequency limit. We have measured the shot noise properties of the single electron transistor with high tunnel barrier transparencies, as a function of bias voltage and gate charge and find a good agreement with the orthodox theory for single electron tunneling.