Research on hetero-structure growth by a supersonic source beams and an atomic layer epitaxy.

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Basic research on the hetero-structure growth was carried out for various materials including semiconductors, insulating materials, and metals. It is important for the growth of a high quality hetero-interface to precisely control the surface migration of the precursors and the nucleus in the first stage of the hetero-growth. It was found that the control of these parameters was difficult for the conventional growth method such as molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). Therefore, a new growth method using "a supersonic source beam method" and "an atomic layer epitaxy" was developed for the precise growth control. This new method made it possible to independently control the surface migration of precursors from other growth parameters such as growth temperature. By using this growth method, we could produce an extremely high density of nuclei (three order higher than the conventional growth) in the first stage of the hetero-growth.We could select the kind of nuclei useful for the hetero-growth and control its density in the first stage of the growth. After this process, we grew the hetero-structures including semiconductor/semiconductor hetero-structures and semiconductor/metal hetero-structures by the atomic layer epitaxy (Pulsed-Jet-Epitaxy). The atomic layer epitaxy enabled us to control the layer-by-layer growth at an atomic level, which was found for growing a high quality hetero-structure. Furthermore, we could control the dislocation and the relaxation of the interface strain by the atomic layer epitaxy. From these basic research, we could grow high quality hetero-structures for various material systems.