FUNDAMENTAL RESEARCH FOR QUANTUM DEVICES CONSTRUCTED WITH MULTI-LAYERS OF VERY THIN EPITAXIAL Al2O3 AND Si

绝缘层在硅上的异质外延生长和单晶硅在这些绝缘层上的连续生长对绝缘体上硅（SOI）结构的形成具有重要意义。我们提出了γ-Al2O3薄膜作为绝缘体材料，并在Si衬底上获得了高质量的γ-Al2O3层。在我们小组中，我们已经研究了SOI（Silicon On Insulator）结构，并提出了外延γ-Al2O3薄膜作为绝缘体材料。采用Al固体源和N2O气源混合源MBE研究了γ-Al2O3的外延生长。利用杂化源MBE在Si衬底上成功地生长出了无碳污染的极薄、极平的γ-Al2O3薄膜。由于Al2O3绝缘子稳定，这种结构适用于通常的Si工艺。因此，γ-Al2O3有望成为一种替代SiO2的绝缘膜。目前，本课题组正在研究γ-Al2O3在MIS型场发射体中的应用。此外，由于Si和γ-Al2O3易于形成多层结构，因此可以在量子效应器件中得到更多的应用。γ-Al2O3和Si的极薄膜生长控制对于形成量子阱结构是非常必要的。因此，本研究的目的是控制纳米厚度的生长，以及Si和γ-Al2O3形成量子阱结构。由Si和绝缘膜组成的量子阱结构可以锁定高能电子，因为使用了对Si具有大势垒高度的绝缘膜。因此，Si和γ-Al2O3的量子阱结构在发射恒定电子能量的发射体中具有潜在的应用前景。计算结果表明，必须实现硅膜厚度控制在4nm以下。随着γ-Al2O3的生长，直接生长的γ-Al2O3在Si上的电绝缘性能较差。而采用Al2O3预层法制备的3nm厚的γ-Al2O3可实现5MV/cm左右的速率。通过这种生长方法，实现了对具有良好绝缘性能的极薄（3nm厚）γ-Al2O3薄膜的生长控制。迄今为止，Si2H6气体酱料用于Si生长，但无法将膜厚度控制在几个nm以内。为此，介绍了一种低生长速率的微型光束蒸发器装置。因此低速生长（4nm/h）成为可能。但硅表面的平整度问题仍然存在。因此，我们提出了用Al终止γ-Al2O3表面的方法，即先沉积Al，然后在800℃下退火。通过这种方法，在Si生长的早期阶段，我们成功地抑制了Si的三维生长。Al2O3预层和Al预沉积形成了γ-Al2O3 (3nm)/Si (lll) (4nm)/γ-Al2O3 (3nm)/Si （lll）结构。然后，对其电特性进行了评价。结果，在室温下证实了负电阻。少

Heteroepitaxial growth of insulating layers on Si and the successive growth of a single crystalline Si on those insulating layers are of great interest in the formation of silicon-on-insulator (SOI) structures. We have proposed γ-Al2O3 films as an insulator material and obtained high quality layers of γ-Al2O3 on Si substrates. In our group, we have already studied SOI(Silicon On Insulator) structures, and have proposed an epitaxial γ-Al2O3 film as insulator material. The epitaxial growth of γ-Al2O3 was investigated with the hybrid source MBE using Al solid source and N2O gas source. Very thin and very flat γ-Al2O3 films without carbon contamination were grown on Si substrates successfully by the hybrid source MBE.This structure is suitable for the usual Si process due to stable Al2O3 insulator. So γ-Al2O3 is being expected of an insulation film which can be substituted for SiO2. At present, our group are studying application to MIS type Field Emitter of γ-Al2O3. Furthermore, applicatio … More ns to quantum effect devices can be expected because multiple layer structure by Si and γ-Al2O3 can be formed easily. The very thin film growth control of γ-Al2O3 and Si becomes very necessary to form a quantum well structure. Therefore, the purpose of this study is the growth control of nm-thickness, and the formation of the quantum well structure by Si and γ-Al2O3. The quantum well structure composed of Si and an insulation film can be expected to lock up electrons of the high energy, because an insulation film with a large barrier height to Si was used. So the quantum well structure by Si and γ-Al2O3 has a potential application to an emitter which can emit a constant electron energy. As a result of the calculation, the thickness control of the Si film in less than 4nm must be realized. As growth of γ-Al2O3, an electrical insulation property of directly grown γ-Al2O3 on the Si was poor. But about 5MV/cm was realized using a 3nm-thick γ-Al2O3, which was prepared by Al2O3 pre-layer method. The γ-Al2O3 growth control of very thin film (3nm-thick) with good insulation property was realized by this growth method. Until now, Si2H6 gas sauce was used for the Si growth, but the control of film thickness of a few nm was impossible. So, the Mini-beam evaporator device with a low growth rate was introduced. So low speed growth (4nm/hour) became possible by this method. But a problem in Si surface flatness was still remained. So we proposed that termination of a γ-Al2O3 surface with Al, which is at first, deposition of Al, then annealing with 800℃. By this method, at the early stage of the Si growth, we succeeded in the repression of three-dimensional growth of Si. A γ-Al2O3 (3nm) /Si (lll) (4nm)/γ-Al2O3 (3nm)/Si (lll) structure was formed with Al2O3 pre-layer and Al pre-deposition. Then, the electrical characteristics were evaluated. As a result, a negative resistance was confirmed at room temperature. Less