Fundamental Study of Ultra-High Speed Electron Devices with Metal-Insulator Single-Crystalline Ultra-Thin Layrs

本课题是利用金属和绝缘体实现超高速电子器件的基础性研究。为此，我们从理论上和实验上研究了纳米厚金属和绝缘体构成的超晶格的物理性质，以及用该材料体系制备的高速运行电子器件的基本性质。本项目取得的成果总结如下：提出了一种以金属-绝缘体超晶格为材料体系的新型量子效应高速电子器件。为了实现该装置，我们首先建立了以硅化钴和氟化钙为原料的金属绝缘体超薄异质结构晶体生长技术。利用该技术制备了金属绝缘体谐振隧道二极管和热电子晶体管，并首次实现了器件的基本工作原理。阐明了金属绝缘体量子阱谐振能级的结构依赖性，这是实现该器件所必需的。制作了谐振隧道晶体管，并实现了其晶体管动作。通过比较三势垒隧道谐振二极管负差分电阻的理论和实验结果，研究了金属绝缘体量子阱谐振能级的结构依赖性。关于负差分电阻处外加电压与谐振点数的阱宽关系，一个具有自由电子质量的理论与观测结果很好地吻合。根据这一结果，设计所提出的器件的谐振电平成为可能。对于谐振隧道晶体管，通过建立主要包括基极与绝缘层之间超薄金属层接触的制造工艺，在77K时在金属-绝缘体系统中实现了具有负差分电阻的第一个晶体管动作。这些基本的理论和实验结果是实现金属和绝缘体超高速电子器件量子效应的重要一步。少

This research project is a fundamental study towards realizing ultra-high speed electron devices with metal and insulator. To achieve this, we investigated theoretically and experimentally on physics of superlattices with nanometer-thick metal and insulator, and also on basic properties of electron devices for high-speed operation fabricated with this material system. Results obtained in this project are summarized as follows.A novel quantum-effect high-speed electron device was proposed assuming metal-insulator superlattice as the material system. To realize this device, we established crystal growth technique of metal-insulator ultra-thin heterostructure using cobalt silicide and calthium fluoride at first. Using this technique, metal-insulator resonant tunneling diode and hot electron transistor, both of which are basic components of the proposed device, were fabricated and their principle operation was achieved for the first time. The structural dependence of the resonant levels of … More the metal-insulator quantum well, the study of which is essential for the realization of the proposed device, was clarified. A resonant tunneling transistor was also fabricated and its transistor action was achieved.The structural dependence of the resonant levels of the metal-insulator quantum well was investigated by comparing theoretical and experimental results of the negative differential resistance observed in the triple-barrier resonant tunneling diode. With respect to the well width dependenceof the applied voltage at negative differential resistance and the number of the resonance points, a theory with the free-electron mass agreed well with the observation. From this result, design of the resonant levels for the proposed device became possible. For the resonant tunneling transistor, the first transistor action with negative differential resistance was achieved at 77K in the metal-insulator system by the establishment of the fabrication process including mainly the contact of the base electrode to the ultra-thin metal layr betweenthe insulator layrs.These basic results of theory and experiment are an important step towards realizing quantum-effect ultra-high speed electron devices with metal and insulator. Less