Study of electronic states in quantum ring structures by means of terahertz radiation

我们制作了不同尺寸的单量子环结构和环阵列结构来研究量子环结构中的电子态。对于环形结构的制作，采用了电子束光刻和湿法刻蚀技术来制作GaAs/AlGaAs异质结。在制作的尽可能小的单环结构中，在4.2K的磁阻测量中可以观察到Aharonov-Bohm振荡。此外，在微波辐照下，我们发现在回旋半径等于几何定义的环半径的磁场处有一个新的宽峰。在几种不同环大小的环结构中出现的宽峰表明环结构中的电子对微波的吸收。电子通过环的行进调谐比所用微波的周期短得多。这一实验结果表明，至少在调谐周期内，在磁场作用下环中局域电子的存在比微波的一段时间要小。为了增加电阻，局域电子必须与环上的导电电子相互作用。观察到的辅助峰可以用量子环中局域电子的存在来解释。这一实验结果适用于螺旋型天线和自旋晶体管的发展，这些晶体管可以工作在像微波一样的高频。为了将量子环应用到天线上，我们尝试用Ge：Te制作蜗牛固体发光体。为了将量子环应用于自旋电子场，我们还研究了另一种III-V化合物异质结InGaAs/InAlAs和InGaSb/InAlSb的电子态。在这一阶段，我们得出结论：InGaAs/InAlAs异质结适合制作量子环结构，用于自旋晶体管的开发

We fabricated various sire of single quantum ring structures and ring array structures to investigate the electronic states in the quantum ring structures. For the fabrication of the ring structures, e-beam lithography and wet etching techniques was employed to GaAs/AlGaAs heterostructures. In the fabricated single ring structures being as small as possible, Aharonov-Bohm oscillation could be observed in the magnetoresistance measurements at 4.2 K Furthermore, under irradiation of microwaves, we found a new broad peak of resistance at the magnetic field at which the cyclotron radius equals to the geometrically defined radius of the ring. The appearance of the broad peak in several ring structures with different ring size indicates the absorption of the microwaves due to the electrons in the ring structure. The traveling tune of electrons through a ring is much shorter than the period of the applied microwaves. This experimental result suggests that the existence of the localized electrons in the ring at the magnetic field at least for the tune mare than a period of the microwaves. For the increasing of the resistance, the localized electrons have to interact with conducting electrons tough the ring. The observed assistance peak can be explained by the existence of the localized electrons in the quantum ring.This experimental results apply to the crew type of anntena and the development of spin transistors which can work at high frequency like microwaves. For the application of the quantum ring to the anntena, we tried to make snail solid state light emitter with Ge : Te. For the application of the quantum, ring to the spintronics field, we also investigated the electronic states of the another III-V compound heterostructures, InGaAs/InAlAs and InGaSb/InAlSb heterostructures. In this stage, we concluded that InGaAs/InAlAs heterostructures is suitable for making a quantum ring structure for the development of spin transistors