Transport measurements at cryogenic temperatures through a few-electron top gated quantum dot fabricated in a silicon/silicon-germanium heterostructure are reported. Variations in gate voltage induce a transition from an isolated dot toward a dot strongly coupled to the leads. In addition to Coulomb blockade, when the dot is strongly coupled to the leads, the authors observe the appearance of a zero bias conductance peak due to the Kondo effect. The Kondo peak splits in a magnetic field, and the splitting scales linearly with the applied field. They also observe a transition from pure Coulomb blockade to peaks with a Fano line shape.
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The curve through the Ohmic contacts is linear with a two-point contact resistance of , measured with all the metal gates floating. This contact resistance includes of line resistance incorporated for filtering out microwave radiation and maintaining a low electron temperature. These series resistances act as a voltage divider with the quantum dot, causing most of the voltage to drop across the series resistance when the dot resistance is low (that is, when it is strongly coupled to the leads).
