ELASTIC RELAXATION IN COMPOSITIONALLY-MODULATED THIN FOILS.

Compositionally-modulated semiconductors are materials of great interest, examples being spinodally decomposed quaternary semiconductors and superlattices. One oft-neglected aspect of the metastability inherent in such systems is that when in thin film form elastic energy can be reduced by near-surface relaxation. Using TEM the authors have studied two important systems - spinodally decomposed In//xGa//1// minus //xAs//yP//1// minus //y layers grown by LPE, and strained-layer superlattices. It is pointed out that when relating high resolution microscopy measurements of lattice parameter to bulk properties, a major correction due to relaxation must be included. This has particular relevance for TEM measurements of the tetragonal distortion in strained layer superlattices.