AFM (top) and KPM (bottom) images of n-InAs/p-InAsSbP based infrared LED cross-section. Scanning Kelvin Probe Microscopy permits to locate the p-n junction, though the potential difference here is only about 20 mV. Such localization is difficult to perform with any other technique.
Sample of infrared diode cleavage and images courtesy of Alexander Ankudinov (group of A.Titkov), Ioffe Physico-Technical Institute, St. Petersburg, Russia