Investigation of p-n junction and dopant profiles in InP-based laser by low voltage SEM

In recent developments in SEM instrumentation and theoretical understanding low voltage (~1KeV) SEM technique (LVSEM) is increasingly becoming a powerful tool to image dopant profiles in semiconductors. LVSEM has demonstrated that doped regions in semiconductor can give rise to constrast in secondary electron (SE) images without aid from a chemical delincation method. In this paper, preliminary LVSEM observation of the p-n junction and dopant profile in InP based laser structure has been made. The SE contrast profiles are compared to secondary ion mass spectroscopy result of atomic concentration of the selected dopant species, for the first time, in InP system. The ability of the LVSEM to image p-n junctions and its contrast sensitivity to doping variations has made it possible to characterize selective regrowth processes. SEM images provide a complete two-dimensional map of CMBH-lasers with p-n current blocking layers and gibes important information on the topography dependent doping distribution around the regrowth area. The results support the conclusion that SE imaging in SEM can be used as a simple and powerful technique for obtaining one- and two-dimensional profile of dopant distributions in InP-based devices.