Study of tunneling currents through germanium quantum-dot single-hole and -electron transistors

The transport properties of Ge quantum-dot (QD) single-hole and -electron transistors (SHTs/SETs) are experimentally investigated. The tunneling currents of Ge-SETs and -SHTs could be modulated by adjusting top Si layer thickness on silicon-on-insulator substrates or applying back-gate biases due to parasitic transistors effect. The Coulomb oscillation of tunneling current is stable with respect to temperature, indicating the observed current should go through the energy levels of a Ge QD but not through trap states. The kp method has been employed to calculate the hole energy levels of a spherical Ge QD to clarify the homogeneous oscillation current characteristic of SHTs.