Two-dimensional carrier profiling of InP structures using scanning spreading resistance microscopy

Scanning spreading resistance microscopy (SSRM) is an analytical technique originally developed for measuring two-dimensional carrier distribution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value derived from the measured electrical current is a function of the local carrier concentration at the surface region surrounding the probe’s tip. In this letter, we report the successful application of SSRM to the analysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structure in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry depth profiles shows good qualitative agreement. SSRM analysis of InP-based device structures was found to be much simpler than that of Si structures: there is no need for surface preparation of the cleaved surface, a lower tip force is required, and metal tips, rather than doped diamond can be used. © 1998 American Institute of Physics.