Disorder-induced resonant tunneling in planar quantum-dot nanostructures

Planar quantum-dot nanostructures have been shown to exhibit resonant features in their near-threshold conductance characteristics. However, the data often display strong nonuniformity in peak amplitude and a lack of reproducibility between devices, which suggests the presence of an influential disorder mechanism. In the present investigation, we perform a three-dimensional numerical analysis of structural disorder in a thin-gated quantum-dot nanostructure. The experimental conductance data for this device exhibit robust resonant features above T=4.2 K despite the presence of extremely wide tunneling barriers. A self-consistent simulation of the device in the virtual-crystal approximation shows no resonant features in the I-V characteristic, thereby excluding any direct influence of the quantum dot. Activating structural disorder in the simulation via interface and surface roughness, however, gives rise to resonant features that strongly resemble the experimental data. We thereby demonstrate that disorder mechanisms in planar nanostructures have a profound influence on near-threshold carrier transport to the extent that they may dominate the effects of intentionally fabricated confinement features.