Characterization and suppression of low-frequency noise in Si/SiGe quantum point contacts and quantum dots

We report on the effects of a global top gate on low-frequency noise in Schottky gate-defined quantum point contacts (QPCs) and quantum dots (QDs) in a modulation-doped Si/SiGe heterostructure. For a relatively large top gate voltage, the QPC current shows frequent switching with 1/f(2) Lorentzian type charge noise. As the top gate voltage is decreased, the QPC pinch-off voltage becomes less negative, and the 1/f(2) noise becomes rapidly suppressed in a homogeneous background 1/f noise. We apply this top-gating technique to double QDs to stabilize the charge state for the electron number down to zero. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4799287]