EFFECT OF A CHARGED SCANNED PROBE MICROSCOPE TIP ON A SUBSURFACE ELECTRON-GAS

Using a cryogenic scanned probe microscope (SPM) one can locally modif y the sheet density of a two-dimensional electron gas (2DEG), and imag e the ballistic flow of electrons through a point contact in the 2DEG located beneath the surface of a GaAs/AlGaAs heterostructure. We calcu late the capacitively induced change in sheet density when a charged S PM tip is brought into contact with a semiconductor heterostructure co ntaining a two-dimensional electron gas. A simple scattering model, ba sed on a local change in sheet density, is used to analyze experimenta l data taken with the SPM method described above. (C) 1996 Academic Pr ess Limited