Transport of electron-waves and single-charges in semiconductor nanostructures

A number of experiments performed in submicron semiconductor structures are described. The submicron structures are defined in the two Dimensional Electron Gas (2DEG) of a GaAs/AlGaAs heterostructure by means of metallic gates which are fabricated on top of the heterostructure. Applying negative voltages to the gates depletes the electron gas beneath them, leaving free electrons only in the ungated regions. A split gate geometry with an opening and a length of a few 100 nm induces a channel in the 2DEG, which is short and narrow compared to the elastic mean free path in the 2DEG. The transport through such a constriction is, therefore, ballistic. The Fermi wave length of the electrons is about 50 nm and, therefore, is also of the order of the constriction width, so the electron wave nature affects the transport properties. The quantum ballistic transport regime in these submicron devices is addressed and charging effects in semiconductor quantum dots are discussed.