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

在绝缘体上硅（SOI）结构的形成中，绝缘层在Si上的异质外延生长以及单晶Si在这些绝缘层上的连续生长具有极大的兴趣。我们提出了γ-Al_2O_3薄膜作为绝缘体材料，并在Si衬底上获得了高质量的γ-Al_2O_3薄膜。本课题组研究了SOI（Silicon On Insulator）结构，提出了外延γ-Al_2O_3薄膜作为绝缘体材料。采用Al固体源和N_2O气体源的混合源分子束外延生长γ-Al_2O_3。利用混合源分子束外延技术在Si衬底上成功地生长出了无碳污染的超薄、平整的γ-Al_2O_3薄膜，由于Al_2O_3具有稳定的绝缘体，这种结构适合于通常的Si工艺。因此，γ-Al_2O_3有望成为替代SiO_2的绝缘薄膜。本课题组目前正在研究γ-Al_2O_3在MIS型场致发射中的应用。此外，应用 ...更多信息 由于Si和γ-Al_2 O_3的多层结构易于形成，有望成为ns量子效应器件。为了形成量子阱结构，必须控制γ-Al_2O_3和Si的薄膜生长。因此，本研究的目的是纳米厚度的生长控制，以及由Si和γ-Al 2 O3形成量子阱结构。由Si和绝缘膜组成的量子阱结构可以预期锁定高能量的电子，因为使用了对Si具有大势垒高度的绝缘膜。因此，Si和γ-Al_2 O_3量子阱结构在制备具有恒定电子能量的发射体方面具有潜在的应用前景。计算结果表明，Si膜的厚度控制在4 nm以内是必须的。作为γ-Al 2 O3的生长，在Si上直接生长的γ-Al 2 O3的电绝缘性差。而用Al_2O_3预层法制备的3 nm厚的γ-Al_2O_3薄膜，其膜厚可达5 MV/cm。用这种方法可以控制γ-Al_2O_3薄膜的生长，得到厚度为3 nm、绝缘性能良好的薄膜。到目前为止，Si的生长使用Si 2 H6气体酱料，但不可能将膜厚控制在几nm。因此，低增长率的微束蒸发器装置被引入。因此，低速生长（4 nm/小时）成为可能，通过这种方法。但硅表面平整度仍存在问题。因此，我们提出了用Al终止γ-Al_2O_3表面的方法，即先沉积Al，然后在800℃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。采用Al_2O_3预层和Al预沉积的方法制备了γ-Al_2O_3（3 nm）/Si（111）（4 nm）/γ-Al_2O_3（3 nm）/Si（111）结构。然后，评价电特性。结果，在室温下确认了负电阻。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