The focus of this chapter is a discussion of transport in quantum dots, which are quasi-zero-dimensional nanostructure systems whose electronic states are completely quantized. The confinement of carrier motion in these structures is imposed in all three spatial directions, resulting in a discrete spectrum of energy levels much the same as in an atom or molecule. We can therefore think of quantum dots as artificial atoms, which in principle can be engineered to have a particular energy level spectrum. As in atomic systems, the electronic states in quantum dots are sensitive to the presence of multiple electrons due to the Coulomb interaction between electrons. Rich transport phenomena are therefore observed in these structures, not only because of quantum confinement and the resonant structure associated with this confinement, but also due to the granular nature of electric charge.

In contrast to quantum wells and wires, quantum dots can be sufficiently small that the introduction of even a single electron is sufficient to dramatically change the transport properties due to the charging energy associated with this extra electron. One of the main consequences of this charging energy is to give rise to a Coulomb blockade of transport, where conductance oscillations are observed with the addition or subtraction of a single electron from a quantum dot, which we discuss in detail in Sections 6.1 and 6.2.