We report strong transmission electron microscope (TEM) contrast betweenp‐,i‐, andn‐doped InP layers in semiconductor laser diodes. For doping concentrations ∼1018cm−3, contrast levels on the order 30% are observed betweenp‐ andn‐type layers. A critical feature of these experiments is that the samples imaged in the TEM are relatively perfect, plane‐parallel sided membranes fabricated with a focused ion beam. This technique offers the ability to detect and map doping variations with nm‐scale resolution, simultaneously with the other compositional and defect information inherent to TEM. ©1995 American Institute of Physics.