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

We present experimental images and computer simulations of electron and con duction-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 trajecto ries to generate the experimental images. In a weak magnetic field, the ima ges revealed cyclotron orbits allowing a measurement of electron and conduc tion-band-hole energies. Using the same technique, a scattering site caused a 26 degrees change in the trajectories. Computer simulations with localiz ed charge fluctuations in the donor layer, which locally distort the conduc tion band by 24% of the Fermi energy, reproduced structures seen in the exp erimental images and features in a related magnetic steering experiment. Co nduction-band-holes are holelike quasiparticles in the conduction band with an energy less than the Fermi energy, being equivalent to unoccupied elect ron states.