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

异质结构生长的基础研究是针对包括半导体、绝缘材料和金属在内的各种材料进行的。在异质生长的第一阶段，精确控制前驱体和晶核的表面迁移对于高质量异质界面的生长至关重要。结果发现，这些参数的控制是很难的常规生长方法，如分子束外延（MBE）或金属有机化学气相沉积（MOCVD）。因此，一种新的生长方法，使用“超声源束法”和“原子层外延”的精确生长控制开发。这种新的方法使得有可能独立地控制从其他生长参数，如生长温度的前体的表面迁移。通过这种生长方法，我们可以在异质生长的第一阶段产生极高的晶核密度（比常规生长高三个数量级），我们可以在生长的第一阶段选择对异质生长有用的晶核种类并控制其密度。在此过程之后，我们生长的异质结构，包括半导体/半导体异质结构和半导体/金属异质结构的原子层外延（脉冲喷射外延）。原子层外延使我们能够在原子水平上控制逐层生长，这被发现用于生长高质量的异质结构。此外，我们可以通过原子层外延来控制位错和界面应变的弛豫。通过这些基础研究，我们可以为各种材料系统生长高质量的异质结构。

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.