Effects of beam-specimen interaction on the observation of reverse-biased junction

Electron interferometry experiments on straight reverse-biased p-n junctions have been carried out in a transmission electron microscope. The trend of the interference fringes as well as the shape of the interference region are able to give direct information about the phase variation across the junction. Agreement between theory and experiment is obtained by introducing a suitable surface density charge produced by the beam at the interface between the silicon and the native oxide. Also the depletion layer width and the overall electric field topography are strongly modified by the charged layers. The results confirm the main predictions of the improved model in a more reliable way than those obtained through previous out-of-focus observations and point out the active role of the electron beam in the electric characterization of semiconductor devices.