Characterization on near-surface electronic properties and investigation of electron transport mechanisms in InAs nanostructures studied by nano-probes

点击翻译按钮获取中文摘要

We fabricated InAs wire structures and thin films on GaAs giant steps formed on GaAs (110) vicinal substrates as well as InAs self-assemble quantum dot structures on GaAs (001) substrates, and characterized them by means of nano-probe methods such as laser-illuminated STM and conductive tip AFM systems. First, in the laser-illuminated STM, we measured the photo-response on the differential conductance by the superposing the small ac bias to the dc bias under the height control condition from the tunneling current, and we succeeded in visualizing the InAs wire regions in the photo-response images of the differential conductance. Similarly in the current measurements by the conductive tip AFM under the laser illumination, we observed the photo-current enhancement on the InAs regions and the modulation of the capacitive coupling strength between the tip and the sample separated by the surface depletion layers due to the photo-carriers, which informed us the photoabsorption properties and … More the near-surface band diagrams on the single nanostructures. Secondly, we introduced the non-contact mode Kelvin probe force microscopy (KFM) operated in high vacuum, in which the surface potential could be determined from the electrostatic force working between the tip and the sample surface, and we pointed out the importance of the reduction in both the mechanical vibration amplitude of the KFM cantilever as well and the average separation between the tip and the sample to improve the reliability in the potential determination from the two-dimensional theoretical simulations and as well as the experiments. Then we measured the surface potential on the InAs self-assembled quantum dots, showing the dot size dependence of the surface potential, which could be attributed to the carrier accumulation near the InAs surfaces. Finally, we developed the novel method for the quantitative detection of the local current in the very fine structures like InAs wires by using the magnetic force microscopy (MFM), and successfully demonstrated the ac current detection below several ten nA. Less