Interaction between terahertz photons and electron waves in quantum structures and its application to ultra-high frequency devices

本研究的目的是实现一种基于光子辅助隧穿和渡越电子波拍频的新型三端电子器件，用于放大尚未开发的太赫兹频段。主要研究结果如下：选择半导体-绝缘体和半导体-金属-绝缘体异质结构体系（CaF 2/CdF 2/Si和CoSi 2/CaF 2/Si）作为太赫兹器件的材料，研究了其外延生长和器件形成。这些材料系统在高势垒和由此形成便于高速响应的尖锐量子能级的观点上是有利的。通过纳米局域外延和优化退火条件等外延生长技术的发展，首次在Si（100）衬底上制备了CaF 2/CdF 2/Si共振隧穿二极管（RTD），并在室温下获得了高达10^6的峰谷比。在此基础上，研制了二维电子结构的平面器件，并在室温下获得了高的峰谷比。 关于我们 制造了作为所提出的三端太赫兹器件的基本部分的半导体层结构中的ON气体，以确认所提出的器件的原理操作。在毫米波长范围内的操作与理论预测一致。结合上述研究，提出了由RTD和小尺寸太赫兹天线组成的集成太赫兹器件结构。作为将这种结构应用于金属-绝缘体-半导体异质结构的第一步，制备了具有半导体异质结构的RTD，并将其与小尺寸平面天线集成。该器件在室温下振荡频率为1.02THz，振荡模式为谐波振荡。这是迄今为止室温单电子振荡器的最高频率记录，也是第一个超过1 THz的频率，尽管它是谐波振荡。通过对器件结构的优化，实现基频模式的2 THz以上振荡是可行的。这些结果表明，不仅这种结构的半导体RTD可以是紧凑和相干太赫兹源的候选者，而且这种集成结构可以应用于所提出的具有金属-绝缘体-半导体系统的太赫兹器件。少

This research aimed at realization of a novel three-terminal electron device based on photon-assisted tunneling and beat of transit electron waves for amplification of undeveloped terahertz frequency range. The results obtained are as follows.Semiconductor-insulator and semiconductor-metal-insulator heterostructure systems (CaF2/CdF2/Si and CoSi2/CaF2/Si) were chosen for the materials of the terahertz devices, and epitaxial growth and device formation are investigated. These material systems are advantageous in the view point of high potential barrier and resulting formation of sharp quantum levels which are convenient for high speed response. By the development of epitaxial growth technique including nano-area local epitaxy and optimized annealing conditions, resonant tunneling diodes (RTDs) with CaF2/CdF2/Si on Si(100) substrate were fabricated and operated with extremely high peak-valley ratio of 10^6 at room temperature for the first time.A planar device with two-dimensional electr … More on gas in semiconductor layer structure, which is a basic part of the proposed three-terminal terahertz device, was fabricated to confirm the principle operation of the proposed device. The operation in the millimeter wavelength range was in agreement with theoretical prediction. The operation even in the terahertz range was also expected form this result.Together with the above researches, integrated terahertz device structure composed of RTDs and small-size terahertz antennas is proposed. As the first step to apply this structure to metal-insulator-semiconductor heterostructures, RTDs with semiconductor heterosturcutre was fabricated and integrated with small-size planar antennas. This device oscillated at 1.02THz with harmonic oscillation mode at room temperature. This is the highest frequency record, as well as the first over-1THz frequency, of a room-temperature single electronic oscillator to date, although it is the harmonic oscillation. Further more, it was also shown that oscillation over 2THz with fundamental frequency mode was feasible with the optimization of the device structure. These results showed not only that even semiconductor RTD with this structure can be a candidate for compact and coherent terahertz sources but also that this structure of integration can be applied to the proposed terahertz device with metal-insulator-semiconductor system. Less