The Resonant Tunneling Electron Transport through a Quantum Dot and Its Application

研究了电子通过半导体量子点的共振输运机理和单电子晶体管的电流-电压特性。到目前为止，集成电子学中传统器件的进一步小型化已经指出了许多问题，SET作为未来接班人的有希望的候选人越来越受到关注。随着SET器件尺寸的缩小，器件的孤岛部分从经典的热平衡系统转变为具有离散能级的量子力学系统，传统的器件运行理论失去了有效性。我们推导了一个模型哈密顿量，描述了一个仅包含单个自旋简并量子能级的简单缩小SET的性质，并讨论了输运机制。为了提供任意一对栅极偏置和漏极偏置的电流值，绘制了电流图。这样的信息对于将器件应用于电路组成是有用的。结果表明，载流子通过点的流动动力学对电流大小的控制起着重要作用。研究了用硅矩形平行六面体量子点制作的超小型SET模型，并用蒙特卡罗方法模拟了其电流-电压特性。分析了点级结构，特别是点级简并对电流-电压特性的影响。同时研究了温度的影响以及隧道的相对大小与源、漏的关系。这个项目使我们有可能了解在栅极偏置和漏极偏置变化的大范围内，超小型SET的总体（尽管是近似的）器件行为。

The mechanism of the electron resonant transport through a semiconductor quantum dot, and the current-voltage characteristics of a single electron transistor (SET) was investigated. So far, lots of problems have been pointed out for farther down-sizing of the conventional device in integrated electronics, and the SET is attracting an increasing attention as a promising candidate for future successor. As the device size of a SET is scaled down, the island part of the device shifts from a classical system in thermal equilibrium to a quantum mechanical system with discrete energy levels, and the conventional theory of the device operation loses its validity. We have derived a model Hamiltonian describing the property of a simple scaled-down SET including only a single spin-degenerate quantum level, and discussed the transport mechanism. A current map is worked out so as to provide the current value for an arbitrary pair of the gate bias and the drain bias. Such an information is useful for application of the device to the circuit composition. It was shown that the carrier flow dynamics through the dot play an important role in controlling the current magnitude. A more realistic model of an ultra-small SET, fabricated with the silicon rectangular parallelepiped quantum dot is investigated and the current-voltage characteristics is simulated by the Monte Carlo method. The influence of the dot level structure, especially the level degeneracy, on the current-voltage characteristics is analyzed. Also the effect of temperature as well as that of the relative magnitude of tunneling related to the source and the drain is studied. This project has made it possible to understand the overall , though approximate, device behavior of the ultra-small SET for a wide range of the gate bias and the drain bias variation.