Hole transport in coupled SiGe quantum dots for quantum computation

We describe transport measurements on double quantum dot structures formed by trench isolation in a SiGe:Si heterostructure. Three different device geometries are described, and a number of phenomena are observed. Transport measurements at 4.2 K reveal a carrier energy filtering effect accompanying a period doubling in Coulomb oscillations, showing that tunnel barriers can be raised and lowered by application of a gate voltage. Peak splitting in Coulomb oscillations is also observed at 4.2 K, indicating interdot capacitive coupling. The stability diagram for a double dot is mapped out at dilution refrigerator temperatures. In another device, single hole electrometers are fabricated 50 nm away from a double quantum dot, and the ability to measure a single excess charge on the double dot is demonstrated at dilution refrigerator temperatures.