The effects of annealing on the microstructure of HgTe/Hg0.05Cd0.95Te/CdZnTe(211) superlattices (SLs) grown by molecular beam epitaxy have been investigated by high-resolution electron microscopy, and Z-contrast imaging was utilized to study the chemical abruptness of the HgTe/HgCdTe interfaces. Low-temperature annealing at 225 or 250degreesC induced interdiffusion, leading to changes in the well/barrier widths. The SLs became more defective even after 30 min of annealing. The widths of the HgTe well layers increased and the widths of the HgCdTe barrier layers decreased dramatically. Thus, activation of p-type dopants such as arsenic through annealing will be difficult to achieve without degradation of electrical and optical properties. (C) 2004 Elsevier B.V. All rights reserved.