Coulomb Blockade In Monolithic And Monocrystalline Al-Ge-Al Nanowire Heterostructures

We report the realization of Ge single-hole transistors based on Al-Ge-Al nanowire (NW) heterostructures. The formation of these axial structures is enabled by a thermally induced exchange reaction at 350 degrees C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25nm-diameter Ge segment is a quasi-1D hole channel. Its length is defined by two abrupt Al-Ge Schottky tunnel barriers. At low temperatures, the device shows a single hole transistor signature with well pronounced Coulomb oscillations. The barrier strength between the Ge segment and the Al leads can be tuned as a function of the gate voltage V-G. It leads to a zero conductance at V-G= 0V to a few quantum conductance at V-G= -15V. When the gate voltage increases from -5V to -3V, the charging energy is extracted and it varies from 0.39meV to 2.42meV. Published under license by AIP Publishing.