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Benoît Roche

Electronic transport through two donors in a silicon transistors, in both static and dynamic regims

Published on 22 October 2012


Thesis presented October 22, 2012

Abstract:
In this thesis, we studied low temperature silicon devices of nanometer size. In these devices, an electric current can flow through a small number of dopants. We studied the case of two dopants in series which electrostatic potentials are controlled independently by two gate voltages. In static regime, it is possible to perform spectroscopy of electronic doping levels. We measure an energy separation of the first two states for the phosphorus dopants around 10 meV, while this separation is 11.7 meV for dopants diluted in a bulk crystal. This difference is explained by the proximity of dopants with a silicon oxide interface. When the levels of the dopants are modulated by a periodic signal a current is generated by the device. The evolution of the current versus gate voltages is simulated by taking into account the tunnel couplings of the system. At high frequency, when we observe the quantification of electromagnetic energy exchanged with the system, the measured current as a function of the amplitude of the signal applied to the gates is described. This is an experimental evidence of the coherence of an electron shared by two dopants.

Keywords:
Silicon, Dopants, Coupled dots

On-line thesis.