Scanning tunneling microscopy is demonstrated for determining the surface morphology of etched Hg‐based semiconductors. Wet etching of HgTe/CdTe superlattices used a Br‐based etch solution while dry etching used methyl‐free radicals formed by electron cyclotron resonance in a reactive ion etching reactor. Both techniques produced smooth surfaces with random features over large regions. Features ranged in height from 1 to 5 nm for wet etching, while the smoothest dry etched sample had random features with an average height of 40 nm. Near mesa structures, evidence of differential etching was observed between the different composition layers in the HgTe/CdTe superlattices for both wet and dry etched samples. ©1995 American Institute of Physics.