Transmission electron microscopy observations of p–n junctions

Abstract

Defocusing, low-angle selected area diffraction and Foucault technique have been applied, working with a Siemens Elmiskop 101, to the observation of the microelectric field associated to a reverse-biased p–n junction. It is shown that, in order to obtain information about the main features of the total electric field, it is necessary to combine all three methods. The first one yields the location of the depletion layer region and allows the drawing of a map of the leakage field. On the basis of these data it becomes possible to interpret the low-angle electron diffraction pattern and, consequently, to locate correctly the contrast aperture in order to obtain in focus, with the Foucault method, an amplitude contrast due to the microelectric field. The region where the external leakage field or the depletion layer is present is thus detectable in focus.