DAFS Study of Strained III-V Epitaxial Semiconductors

The effect of built-in strain on III-V epitaxial semiconductors has been investigated by Diffraction Anomalous Fine Structure (DAFS). We study two different systems in a different strain regime: a Strained Layer Superlattice of (GaP) 2 (InP) 3 grown on a GaAS(001) substrate, and a single epilayer of GaAs 1 - x P x , (x=0.225), also grown on a GaAs (001) substrate. In the first case the strain is accommodated by plastic deformation of the lattice, while in the second one it is partially relaxed by dislocations generation. The bond distances for the Ga-P and Ga-As pairs are obtained showing how they are affected by strain. The Ga-As pair shows to be softer' than the Ga-P pair, i.e. more available to accommodate strain by bond deformation, in good agreement with previous results obtained by different techniques. The DAFS provide a unique tool of studing systems that are out of the reach of the other X-ray techniques.