锗硅单量子点的耦合和瞬态电学性质研究

【作者】 张翼飞；

【导师】 杨新菊；

【作者基本信息】 复旦大学 ， 凝聚态物理， 2010， 硕士

【摘要】 以半导体量子点为代表的半导体纳米结构在光电子、微电子和单电子器件领域有重要的应用前景。在硅衬底上自组织生长的GeSi量子点由于与成熟的硅集成电路工艺兼容具有特殊的意义。对于GeSi量子点现今的研究主要是集中在对其所表现的各项平均性质的研究,由于量子结构的不均匀性,量子结构的量子效应会被削弱或观测不到,另外也无法得到量子点性质的细节。导电原子力显微镜(Conductive Atomic Force Microscopy)是近年来发展起来的一种可以测量纳米尺度下的形貌和电学特性的测量仪器。它提供了一个在纳米尺度直接研究量子结构性质的手段,并且操作方便快捷,对样品损害微乎其微,使得在纳米范围内对单个量子点的电学性质的研究成为可能。本论文通过CAFM测量了单个锗硅量子点的I-V曲线和电流分布,进而研究了量子点的耦合和瞬态电学性质,主要结果如下：1.本文研究了自组织生长的锗硅双层量子点/高密度量子点的耦合。通过测量单层和双层的,不同面密度的量子点样品的I-V曲线和电流分布,得到了双层量了点的层间耦合与密集量子点的层内耦合对于量子点输运性质的影响。在室温下观察到竖直方向分层的多层量子点存在层间耦合,密集排布的量了点存在横向耦合。2.在研究单个量子点的电流电压特性时,发现了快速扫描时有回扫电流峰存在。这个现象可能对应着量子点的充放电过程。本文通过建模研究了回扫电流峰产生的原因。同实验结果相比较,从电流峰所在的位置等参数和扫描的速度,方向,电压范围,时间对回扫峰的影响上都很吻合,能较合理的解释回扫峰现象。更多还原

【Abstract】 Semiconductor nanostructure shows great potential in application areas as opto-electronics, micro-electronics, and single-electron devices. Self-assembled GeSi quantum dots have one of major advantages of its compatibility with conventional Si integrated-circuit technology. Recent research on GeSi QDs concentrated on its average properties, which neglects the details on a single quantum dot.Conductive AFM (Conducive Atomic Force Microscopy) is a recently developed nanometer scale measurement which can get the morphology and electrical properties of nanoscale and has wide application in measuring microscopic properties of the samples. It makes direct investment of the electrical property of one single QD possible.In this paper, we studied coupled GeSi QDs and the transient charging of a single QD using CAFM. Main results are as follows.1. Multi-layer quantum dots shows vertical coupling effect, at the same time, quantum dots on the same layer shows lateral coupling effect when the density of the dots are high enough. In this paper,we looked into the coupling effect of multi-layer/densely packed GeSi QDs。We measure the I-V curve and current map of single-layer/multi-layer/high density/low density samples. We investigated and compared the coupling effect showed in their electrical properties.2. A novel current peak has been observed in the current-voltage characteristics measured on individual GeSi quantum dots in earlier research. The current peaks are detected only during the backward voltage sweep immediately after a forward sweep. This phenomenon is assumed to be due to the charge and uncharged process of the quantum dot. To prove this, we use a mathematical model to simulate this phenomenon. Compared to the experimental data, in which the current peak position and intensity are found to depend strongly on the voltage sweep conditions, the model works well.更多还原