Probing Electronic Structures of Ge Quantum Dot/SiN Barriers in Few-Hole Regime Using Drain Bias-Dependent Tunneling Current Spectroscopy

We reported energy-level distribution of Ge quantum-dot (QD)/Si₃N₄ barrier system using drain bias-dependent tunneling-current spectroscopy of single-hole transistors (SHTs). The studied SHT comprises a spherical Ge QD, self-organized tunneling barriers of Si₃N₄, and self-aligned p⁺-Si source/drain. Thanks to strong confinement, tunneling-current spectra features Coulomb blockade peaks with peak-to-valley ratios of 10-100 over a wide range of hole number. Addition energy has a large maximum for N+2, N+4, N+7 and N+10 as a result of 3D symmetrical potential barrier around the Ge QD. Extracted energy-level spacing and intra-level charging energies of 25-40 meV are large and conducive for improving charge sensitivity.