SCANNING SINGLE-ELECTRON TRANSISTOR MICROSCOPY - IMAGING INDIVIDUAL CHARGES

A single-electron transistor scanning electrometer (SETSE)-a scanned p robe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a sm all fraction of an electron-has been developed. The active sensing ele ment of the SETSE, a single-electron transistor fabricated. at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1-xAs h eterostructure sample show individual photo-ionized charge sites and f luctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potenti als at submicrometer length scales on the surface of this semiconducto r sample.