Distribution of As atoms in InP/InPAs(1 ML)/InP hetero-structures measured by X-ray CTR scattering

Samples of InP/InPAs(1ML)/InP were prepared by OMVPE. The interfaces of these samples were investigated by X-ray CTR measurement. The distributions of As atoms around the interfaces were clearly revealed in the atomic scale from the data. It was shown that As atoms extended into only a few MLs under the InPAs. As atoms contained in the InPAs hetero-layer were almost the same as those extended in the InP cap layer. These results suggest that the extension of As atoms in the InP layer occurs due to the absorbed As atoms on the InPAs surface or As atoms remaining in the gas phase. Thus the source-gas flow sequence should be finely controlled to realize abrupt InP/InPAs interfaces