Few Electron Si/SiGe Quantum Dots

Fully top-gated silicon/silicon-germanium quantum dots have been fabricated and characterized at low temperatures. For the quantum dots with few electron occupation, by varying the gate voltages two regimes may be accessed: at large negative voltages sharp Coulomb diamonds and classical Coulomb blockade is observed with a charging energy of 3.8 meV. At more positive gate voltage, co-tunneling features appear and a zero-bias conductance anomaly is observed with a behavior closely resembling the quantum dot Kondo effect. The increased zero-bias conductance vanishes with increasing temperature, and this peak splits into two peaks at finite drain-source voltage with increasing perpendicular magnetic field. The peak splitting increases linearly with increasing magnetic field. We discuss the various conductance regimes and the application of these types of quantum dots for quantum information processing.