Chapter 2 - Electronic transport properties of quantum dots

Abstract

This chapter provides a discussion on vertical quantum dots. Both the basic theory and the experimental data for the electron spectroscopy as a function of magnetic field and temperature for two vertical quantum dot systems, the fabricated quantum dot and the impurity quantum dot have been presented. Current steps in the I(V) characteristics are observed in both systems. In the fabricated quantum dot, these steps are due to the discrete nature of the 0D dot density of states. In the impurity system, these steps are attributed to the discrete 0D states resulting from the Coulomb potential of a single or a pair of impurities in the quantum well region. In both systems, in magnetic fields parallel to the current, the step edges exhibit a diamagnetic shift as expected, while a suppression of the current plateaus is observed in magnetic fields perpendicular to the current, which is attributed to the decreasing overlap between emitter and dot wave functions. Using the highly localized dot states as spectroscopic probes, the electronic structure of the emitter electrode is measured through the oscillatory fine structure observed on top of the normal current plateaus of both systems. The fine structure is observed to be reproducible, both upon repeated traces and upon thermal cycling. Variable-temperature results indicate that this fine structure originates from below the Fermi level in the emitter.