SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography and silicon epitaxial-regrowth

A SiGe quantum dot single-hole transistor passivated by silicon epitaxial regrowth with extremely stable Coulomb blockade oscillations has been demonstrated. The quantum dot was defined by atomic force microscopy nanopatterning technique and subsequently passivated by the epitaxial regrowth of silicon. Such passivation of the dot avoids any potential defect states on the dot associated with the SiSi O2 interface. Coulomb blockade oscillations controlled by side planar gating at ∼0.3 K are reproducible, in sharp contrast with the noisy and irreproducible I-V characteristics of unpassivated SiGe quantum dot devices. An additional top gate was used to further tune the Coulomb blockade oscillations, enabling a shift in side-gate voltage of up to three periods.