Scanning tunneling potentiometry of semiconductor junctions

A method for performing scanning tunneling potentiometry of semiconductor heterojunctions is described. The method yields a direct measure of the electrostatic potential distribution across the interface, with microscopic resolution. The measurement is accomplished by scanning the probe tip at constant sample–tip separation across the junction, and adjusting the sample–tip voltage to maintain a constant tunnel current. An example is given of potentiometry across a GaAs pn junction.