Control of propagation velocity of sub-picosecond electrical signals on the micro strip lines involving quantum wells

该项目的主要目的是控制亚皮秒电信号在涉及半导体量子威尔斯的微带线（MSL）上的传播速度，其中电子和空穴通过例如光激发产生。沿着器件的制作和测量，通过使用时域有限差分（FDTD）软件进行电磁场的三维计算。主要结果如下。(1)It发现，在本项目开始时，在半导体衬底上制作的MSL中观察到的电信号是仅由衬底表面上形成的单个信号线波导的电信号。单根金属线的波导在微波和光学领域已有报道。在太赫兹频段，金属复电导率的真实的实部和虚部具有相同的值，可以作为研究金属对电磁场影响的良好系统 关于我们 表面等离子体激元对电磁波导的影响。我们还发现，信号的衰减和色散的沿着单金属线可以甚至低于传统的MSL，如果线被均匀的介质膜覆盖。因此，我们可以预期单线波导的应用前景。(2)We成功地制造了MSL，其中地平面由光学透明导体ITO制成。在这样的MSL中，光接入信号线和接地平面之间的区域是可能的。实验证实，光谱范围低于1 THz的信号可以传输超过1 mm，具有良好的传播特性。我们还表明，使用Drude模型的ITO是必要的精确预测的传播特性的频率高于1太赫兹，FDTD计算的基础上。(3)It实验证实，在使用聚合物电介质的薄膜MSL中，亚皮秒电信号在几mm内的传输是可能的。（4）建立了在上述MSL中嵌入半导体量子威尔斯的方法。在测量中，没有观察到传播速度的控制，主要是因为电子和空穴的激发不足。然而，由于在这项工作中建立的器件制造方法具有良好的通用性，我们可以期待在未来实现功能的MSL的进展。少

The major aim of this project was the control of propagation velocity of sub-picosecond electrical signals on micro strip lines (MSLs) involving semiconductor quantum wells, where electrons and holes are generated by with, for example, optical excitation. Along with the fabrication of the devices and the measurements, three-dimensional calculations of the electromagnetic fields were performed by using finite-difference-time-domain (FDTD) software. The major results are as follows.(1)It was found that the electrical signals observed, at the beginning of this project, in the MSLs made on semiconductor substrates are those waveguided only by the single signal line formed on the substrate surface. The waveguiding by single metallic lines has been reported in microwave and optical regimes. The strip lines in THz-frequency regime, where the real and imaginary parts of the complex conductivity of metals have the values in the same level, can be a good system for the investigation on the influ … More ence of surface plasmons on the electromagnetic waveguides. We also found that the attenuation and the dispersion of the signals along the single metallic line can be even lower than the conventional MSLs, if the line is covered by a uniform dielectric films. Hence we can expect the application of single-line waveguides in the future.(2)We successfully fabricated the MSLs where the ground plane is made of an optically-transparent conductor, ITO. In such MSLs, optical access into the region between the signal line and the ground plane is possible. It was confirmed, experimentally, that the signals whose spectral range is below 1 THz can be transmitted for more than 1 mm with good propagation characteristics. We also showed that the use of Drude model for ITO is necessary for the precise prediction of the propagation characteristics in the frequency higher than 1 THz, on the basis of the FDTD calculation.(3)It was experimentally verified that the transmission of sub-picosecond electrical signals over a few mm is possible in the thin film MSLs in which the polymer dielectric is used.(4)Methods for embedding semiconductor quantum wells in the MSL described above were established. In the measurement, the control of the propagation velocity was not observed, mostly because of the insufficient excitation of electrons and holes. However, since the device fabrication method established in this work has a good versatility, we can expect the progress for realizing functional MSLs in future. Less