Cryogenic scanning probe characterization of semiconductor nanostructures

We demonstrate the use of a scanned probe microscope (SPM) at 4 Kelvin to study electron transport through a ballistic point contact in the two-dimensional electron gas inside a GaAs/AlGaAs heterostructure. The electron gas density profile is locally perturbed by the charged SPM tip providing information about the electron flow through the point contact. As the tip is scanned, one obtains a spatial image of the ballistic electron flux as well as the topographic profile of the structure. Calculations indicate the spatial resolution is comparable to the electron gas depth.