Imaging electron and conduction-band-hole trajectories through one and two series constrictions

A charged scanning probe has been used to investigate electron transport in a two-dimensional electron gas (2DEG) patterned with 1D constrictions in a GaAs/AlGaAs heterojunction at 1.5 K. The probe creates a local perturbation in the 2DEG electrostatic potential capable of scattering transport electrons. A highly collimated hot-electron beam emanating from a single constriction is imaged by backscattering from the probe perturbation. Images of electron and conduction-band-hole cyclotron orbits and small angle scattering sites between two series constrictions are also presented. Conduction-band-holes are positively charged quasi-particles existing below the Fermi energy, which are equivalent to unoccupied electron states.