BOND LENGTHS AT BURIED INASP/INP INTERFACES IN INP/INGAAS MULTI-QUANTUM-WELLS

As K-edge EXAFS has been carried out on InAsxP1-x/InP buried, epitaxial interfaces in strained layer InAsxP1-x/InP superlattices. Very little is known on the local structure of thin semiconductor layers in strained (multi) quantum wells. In particular the question which is still open is to what extent tetragonal distorsion and/or interface strain can alter the known ''rigidity'' of semiconductor bonds. The EXAFS analysis shows that the first shell environment of As at these interfaces is similar to that found in bulk InAsxP1-x alloys of similar composition, as determined experimentally and by comparison with recent theories of bond lengths in semiconductor alloys. In particular we measure an As-In bond length which varies at most 0.02 Angstrom with As concentration at the interface; this implies that epitaxy with InP is accompanied by local structural distortions, such as bond angle variations, which accommodate the nearly constant As-In bond length. For completeness we also report results from high resolution X-ray diffraction and high resolution transmission electron microscopy which confirm the high crystalline perfection of the investigated samples.