Surface potential imaging on InAs low-dimensional nanostructures studied by Kelvin probe force microscopy

We fabricated InAs thin films, wires and self-assembled quantum dots (QDs) on GaAs substrates, and studied their surface potentials by Kelvin probe force microscopy (KFM). The obtained potential images on InAs wires became less distinct as the tip-to-sample distance increased, which can be explained by the broadening of the electric field distribution between the tip and the sample. Such broadening was successfully confirmed by a two-dimensional simulation. We also found that the geometric effect does not mainly dominate the potential contrast on InAs QDs. The surface Fermi levels on the InAs-grown regions on InAs wires and InAs QDs shifted toward the vacuum level because of the electron accumulation in the InAs. Furthermore, the InAs QD size dependence of the potential values was successfully observed. The obtained potential difference between the InAs QDs and the surrounding wetting layer was larger than that obtained between the InAs wires and the surrounding GaAs surfaces, which can be explained by the strong electron confinement effect in the InAs QDs.