Coulomb blockade in monolithic and monocrystalline Al-Ge-Al nanowire heterostructures

M. Sistani (1) , J. Delaforce (2) , K. Bharadwaj (2) , M. Luong (3) , J. Nacenta Mendivil (2) , Nicolas Roch (2) , M. den Hertog (3) , R. B. G. Kramer (2) , Olivier Buisson (2) , A. Lugstein (1) , C. Naud (2)

1 TU Wien - Vienna University of Technology = Technische Universität Wien
2 NEEL - QuantECA - Circuits électroniques quantiques Alpes
3 NEEL - MRS - Matériaux, Rayonnements, Structure

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 °C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25 nm-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 VG. It leads to a zero conductance at VG= 0 V to a few quantum conductance at VG= –15 V. When the gate voltage increases from –5 V to –3 V, the charging energy is extracted and it varies from 0.39 meV to 2.42 meV.

Domains: Materials Science [cond-mat.mtrl-sci]

M. Sistani, J. Delaforce, K. Bharadwaj, M. Luong, J. Nacenta Mendivil, et al.. Coulomb blockade in monolithic and monocrystalline Al-Ge-Al nanowire heterostructures. Applied Physics Letters, 2020, 116 (1), pp.013105. ⟨10.1063/1.5126088⟩. ⟨hal-02524097⟩