Fabrication and characterization of a germanium quantum-dot transistor formed by selective oxidation of SiGe/Si-on-insulator

A simple and CMOS-compatible fabrication method for germanium (Ge) single-electron transistors (SET's) is proposed, in which the Ge quantum dots (QDs) are naturally formed by selective oxidation of Si_0.95Ge _0.0.5/Si wires on a silicon-on-insulator substrate. Clear Coulomb-blockade oscillations, Coulomb staircase, and negative differential conductances are experimentally observed at room temperature. The current-voltage characteristics of Ge SET's indicate that the addition energy of Ge QDs is about 130 meV and the Ge QD's diameter is about 7.7 nm, which agrees well with the transmission electron microscopy observation and numerical calculation.