Localized Electric Field Mapping in Planar Semiconductor Structures

A technique for imaging the 2-D transport of free charge in semiconductor structures is used to directly map electric field distributions in operating devices. Transport imaging is demonstrated in a scanning electron microscope operating in spot mode, using an optical microscope and a high-sensitivity charge-coupled detector to collect resulting luminescence from minority carrier recombination. The field is determined from the ratio of peak intensities in luminescence images with and without an applied electric field. The technique maps the intensity and direction of the electric field with high resolution. Fields are measured for both parallel plate and nonuniform current flow geometries. The results not only show excellent overall agreement with finite-element electrostatics modeling but also demonstrate the ability of the technique to measure the actual profiles that reflect local material variations and contact-related phenomena.