Imaging cyclotron orbits and scattering sites in a high-mobility two-dimensional electron gas

We present experimental images and computer simulations of electron and conduction-band-hole trajectories transmitted between two series constrictions in a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction. The electric perturbation of a scanning charged probe modified the trajectories to generate the experimental images. In a weak magnetic field, the images revealed cyclotron orbits allowing a measurement of electron and conduction-band-hole energies. Using the same technique, a scattering site caused a 26° change in the trajectories. Computer simulations with localized charge fluctuations in the donor layer, which locally distort the conduction band by 24% of the Fermi energy, reproduced structures seen in the experimental images and features in a related magnetic steering experiment. Conduction-band-holes are holelike quasiparticles in the conduction band with an energy less than the Fermi energy, being equivalent to unoccupied electron states.