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

Abstract

Scanning spreading resistance microscopy (SSRM) is a powerful tool originally developed for measuring two-dimensional (2D) carrier distributions in Si device structures with nm spatial resolution. Whereas its application has been explored in detail on Si structures, very little work was made on III–V materials. In this article, we report on the application of SSRM for the analysis of III–V semiconductor structures, and in particular metalorganic chemical vapor deposition-grown InP-based structures. We found that the application of SSRM to InP-based structures is much simpler than to Si. Minimal surface preparation is required, much lower tip forces are needed, and metal tips instead of diamond tips can be used. When imaging complex multilayer epitaxial structures (containing $\mathrm{p,}$ $\mathrm{n,}$ and semi-insulating layers), close agreement between the SSRM profile and secondary ion mass spectroscopy profiles can be obtained. More importantly is the capability of SSRM to image and determine 2D structures in actual devices, such as mesas and trenches, common in semiconductor laser devices. SSRM also proved very valuable in characterizing with high spatial resolution 2D dopant and implant distributions. In this article, we present SSRM analysis of dedicated InP test structures with multiple $\mathrm{p-n}$ layers, varying in concentration level and in thickness.