Local structural investigation of buried InxAs1-xP/InP interfaces

A local structural investigation has been carried out on the 10 angstrom InAsxP1-x layer in ad hoc grown InAsxP1-x/InP epitaxial multistructures deposited by low pressure metallorganic chemical vapor deposition by means of extended x-ray absorption fine structure spectroscopy, high resolution transmission electron microscopy, and high resolution x-ray diffraction analyses. The goal was to characterize the local structure of the unwanted, strained, interface layers of InAsxP1-x produced by the exposure of the InP surface to AsH3 as occurs during the growth of InP/In0.53Ga0.47As heterostructures optimized for photonics. High resolution x-ray diffraction and high resolution transmission electron microscopy confirm the high crystalline perfection of the investigated interfaces. As K-edge extended x-ray absorption fine structure analysis shows, 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 accomodate the nearly constant As-In bond length.