Germanium Spherical Quantum-Dot Single-Hole Transistors With Self-Organized Tunnel Barriers and Self-Aligned Electrodes

We report the fabrication and electrical characterization of single-hole transistors (SHTs), in which a Ge spherical quantum dot (QD) weakly couples to self-aligned electrodes via self-organized tunnel barriers Si3N4. A combination lithographic patterning, sidewall spacers, selfassembled growth was used for fabrication. The core experimental approach is based on selective oxidation poly-SiGe spacer islands located at specially designed included-angle locations Si3N4/Si-trenches. By adjusting processing times conformal deposition, etch back thermal oxidation, good tunability QD size its tunnel-barrier widths were controllably achieved. Each electrically addressable Si gate reservoirs, thus offering an effective building block implementing single-charge devices.