The post-growth structural stability regarding relaxation and defect propagation in Cd0.83Zn0.17Te/Cd0.92Zn0.08Te/Cd0.83Zn0.17Te quantum well (QW) heterostructures grown on [001] oriented Cd0.88Zn0.12Te substrates at 300degreesC by molecular beam epitaxy is investigated. The investigated heterostructures were subjected to post-growth thermal treatment in an ambient atmosphere in a temperature range between 280 and 550degreesC for 3 It each. We have used high-resolution x-ray diffraction as the main characterization tool. High-resolution rocking curves as well as the powerful two-dimensional reciprocal space mapping were employed in both symmetrical as well as asymmetrical reflections. The results indicate that at a post-growth temperature cycle of 350degreesC for 3 h slight modification of the Cd0.83Zn0.17Te/Cd0.92Zn0.08Te barrier/QW heterointerface smoothness is affected. This indicates the onset of migration of Zn atoms at this post-growth temperature time cycle. At 450 degreesC, this effect is more pronounced and seen as the complete disappearance of thickness fringes. For higher post-growth thermal treatment at 550 degreesC for 3 h, a hi-fi relaxation level accompanied by Zn content reduction is observed. A reduction of the Zn content down to 0.11 fractional value in the thick Cd0.83Zn0.17Te barrier is attributed to Zn out diffusion and/or Zn precipitation. (C) 2004 American Vacuum Society.