The epitaxial growth of germanium on silicon leads to the self-assembly of SiGe nanocrystals via a process that allows the size, composition and position of the nanocrystals to be controlled. This level of control, combined with an inherent compatibi
lity with silicon technology, could prove useful in nanoelectronic applications. Here we report the confinement of holes in quantum-dot devices made by directly contacting individual SiGe nanocrystals with aluminium electrodes, and the production of hybrid superconductorsemiconductor devices, such as resonant supercurrent transistors, when the dot is strongly coupled to the electrodes. Charge transport measurements on weakly coupled quantum dots reveal discrete energy spectra, with the confined hole states displaying anisotropic gyromagnetic factors and strong spin-orbit coupling strength with pronounced gate-voltage and magnetic-field dependence.
We investigate the effect of strain on the etching rate of two SiGe wet etchants, namely NH4OH:H2O2 and H2O2. For both etchants, we found that there is no appreciable strain selectivity, i.e. the etching rates do not depend on the actual strain state
in the SiGe films. Instead, for the NH4OH:H2O2 solution, the rates are primarily determined by the Ge content. Finally, we show that both etchants are isotropic with no preferential etching of particular facets.
