InAs自组装量子点GaAs肖特基二极管中的电流输运特性

设计了含有InAs自组装量子点(SAQDs)的新型金属半导体金属隧穿结构,研究了其直流输运特性,观察到了电流迟滞回路现象.这种回路现象是由于紧邻金属肖特基接触的量子点充电和放电引起的,也可以说是由外加电压控制的量子点的单电子过程引起的.分析了量子点总体的充放电特性,量子点中电子在高电场下隧穿出量子点的概率变化决定了量子点的放电过程,而充电过程是由流过量子点层的二极管正向电流决定.理论拟合结果显示充电过程主要由于量子点基态能级俘获电子照成的,激发态对量子点充放电过程只有微弱影响. 关键词： 迟滞现象 自组装量子点 单电子过程     

含InAs自组装量子点肖特基二极管的关联放电效应

制作了含自组织量子点的金属半导体金属双肖特基势垒器件,研究了器件的电流输运特性.在量子点充放电造成的电流迟滞回路的基础上,观察到了电压扫描过程中的电流由低态到高态的跳跃现象.这种电流跳跃来源于充电量子点的关联放电效应.根据量子点系统的哈密顿量,分析了充电量子点关联放电的原因.这种关联放电效应起源于量子点与2DEG的相互作用,当一个量子点放电时通过量子点和2DEG电流的变化会影响其他的量子点,从而促使其放电,这种过程在整个系统中放大导致所有的量子点放电 关键词： 关联效应 自组装量子点     

InAs量子点在肖特基势垒二极管输运特性中的影响

在77到292K的范围内,系统研究了含InAs自组装量子点的金属-半导体-金属双肖特基势垒二极管的输运特性.随着温度上升,量子点的存储效应引起的电流回路逐渐减小.在测试温度范围内,通过量子点的共振隧穿过程在电流电压(I-V)曲线中造成台阶结构,且使电流回路随温度的上升急剧减小.根据肖特基势垒的反向I-V曲线,计算了势垒的反向饱和电流密度和平均理想因子.发现共振随穿效应使肖特基势垒在更大的程度上偏离了理想情况,而量子点的电子存储效应主要改变了肖特基势垒的有效势垒高度,从而影响了势垒的反向饱和电流密度 关键词： 自组装量子点 肖特基势垒 电流-电压特性     

量子点器件的三端电测量研究

利用三端电测量方法，研究了调制掺杂二维电子气结构的量子点器件输运特性.报道了可分别测量二维电子气电阻和量子点隧穿电阻的实验方法.实验结果表明：量子点的横向耦合控制了量子点器件在小偏压下的电输运特性. 关键词： 自组装量子点 二维电子气 量子隧穿 肖特基接触     

倒置器件结构及局域等离子体效应对CdSe量子点LED发光性能的改进

研究了倒置器件结构以及CdSe量子点发光材料与金属纳米粒子之间的相互作用对量子点的电致发光性能的影响。利用TiO₂作为电子传输/注入层,成功地制备了倒置结构的量子点电致发光器件。通过对单载流子器件电压-电流特性的分析,证明了ITO作为阴极到TiO₂的电子注入特性与Al作为阴极时的效果几乎相同。观察到金属纳米粒子产生的局域等离子体效应提高了器件的效率,使得效率随电流增大而降低的速度明显减小。在电流密度为200 mA/cm²时,电致发光器件的效率大约提高了42%。     

硼-碳和硼-氮量子点器件的输运特性研究

用第一性原理研究了硼-碳和硼-氮量子点器件的输运特性以及电流电压特性.研究结果表明相同数量原子组成的硼-碳和硼-氮器件其输运特性及电流电压特性有很大差别.硼-碳器件在Fermi能附近有较大的态密度,而硼-氮器件的能级在Fermi能附近有很大的间隙,Fermi能位于间隙中.从电流特性中可以看出,硼-碳器件表现出导体的特性,而硼-氮器件表现出半导体的特性.     

甚长波量子阱红外探测器的暗电流特性研究

基于载流子在量子结构中的输运理论研究了甚长波量子阱红外探测器(峰值响应波长15μm，量子阱个数大于40)的载流子的输运性质.研究结果表明，在甚长波量子阱红外探测器中，电流密度一般很低，暗电流主要来源于能量高于势垒边的热激发电子.通过薛定谔方程和泊松方程以及电流的连续性方程的自洽求解，发现外加偏压下电子浓度在甚长波器件各量子阱的分布发生较大变化，电场在整个器件结构上呈非均匀分布，靠近发射极层的势垒承担的电压远远高于均匀分布的情形.平带模型假定电压在器件体系上均匀分布，导致小偏压下的理论计算值远远低于实验值. 关键词： 甚长波量子阱红外探测器 量子波输运 暗电流     

一种新型的高频半导体量子点单电子泵

除了直流负电压外,还在浅法刻蚀出的GaAs/AlGaAs量子线上的两个金属指形门上分别叠加两个相位相差π的正弦信号,从而对形成量子点的两个势垒作不等幅调制.在无源漏偏压的情况下,通过周期形成的量子点实现了单电子的搬运.由于新的半导体量子点单电子泵不是依赖库仑阻塞效应通过隧穿进行单电子输运,因此,该器件就不会受到固定隧穿时间引起的低工作频率限制.在1.7K温度下,频率达到3GHz仍然可以观测到量子化电流平台,对应的电流值达到0.5nA量级.这种新器件提供了实现高速度、高精度搬运单电子的另一种可能途径. 关键词： 单电子输运 单电子旋转门 单电子泵 量子化电流平台     

以ZnO为电子传输层PPV的发光

以Ⅱ-Ⅵ族无机半导体ZnO为电子传输层,PPV为空穴传输层和发光层,得到的电致发光器件比单层PPV器件的发光亮度和效率都高.器件结构为ITO/PPV/ZnO/Al的电致发光光谱同单层PPV器件的光谱基本相同,但是启亮电压明显比单层器件低,最大亮度大约比单层器件高6倍左右,同时工作电流也比单层器件小.通过PPV层自吸收现象可判断出发光区域在PPV/ZnO界面处.电流-电压曲线表明,这种器件具有空间电荷限制电流特性,即J∝Vn,这里n大约为2,这器件的电流主要受到空穴的限制.     

量子点环嵌入Aharonov-Bohm干涉器中电子的退耦合态及反共振现象

采用Anderson模型哈密顿量和非平衡态格林函数方法对量子点环以不同构型嵌入A-B干涉器中电子输运的退耦合态及反共振现象进行了理论研究. 结果表明,量子点环A-B干涉器的结构对称性以及穿过A-B干涉器的磁通量是诱发退耦合现象的两种物理机理. 耦合量子点结构的对称性越高,体系在相干电子输运过程中表现出来的退耦合及反共振现象越明显. 而且在具有高度对称性的耦合量子点结构中,通过磁场调节体系的结构参数可以分别使第奇数或第偶数分子本征态从电极上退耦合,从而使电子输运电导表现出奇偶对等振荡现象. 这为设计纳米电子开关器件提供了一个新的物理模型. 关键词： 量子点环 A-B干涉器 退耦合 反共振     

InAs quantum dot field effect transistors

We have studied single electron and hole storage in self-assembled InAs quantum dots (QDs) embedded in GaAs/n-AlGaAs field effect transistors (QD-FETs). We prepared two types of QD-FETs. A single electron and a photo-generated single hole can be stored in each QD in Type 1. In the new Type II, single-electron discharge processes can be controlled by a surface gate voltage (V_g) as well as single-electron storage processes. We demonstrate possible application to novel photo devices and quantum dot memory devices.     

通过纳米硅中量子点的共振隧穿

用纳米硅(nc-Si∶H)薄膜制成了隧道二极管，并在其I-V曲线上发现了不连续的量子化台阶.二极管的I-V曲线可分成二部分：(1)0—7V，电流随外加电压增大而增大；(2)7—9V，电流随外加电压急剧增大并出现三个量子化台阶.量子化台阶的出现直接与纳米硅中的晶粒有关，根据nc-Si∶H的独特结构，对载流子的传导通道进行了讨论；用通过nc-Si∶H中量子点的共振隧穿对I-V曲线进行了初步解释. 关键词：     

Transient Hole Trapping in Individual GeSi Quantum Dot Grown on Si（001） Studied by Conductive Atomic Force Microscopy

Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a certain fast sweep rate range, a novel current peak is observed in the current-voltage characteristics of the quantum dots. The current peaks are detectable only during the backward voltage sweep immediately after a forward sweep. The current peak position and intensity are found to depend strongly on the voltage sweep conditions. This kind of current-voltage characteristic under fast sweep is very different from the ordinary steady state current behaviour of quantum dots measured previously. trapping in the potential well formed bottom Si substrate. The origin of this phenomenon by the quantum dot sandwiched can be attributed to the transient hole between the native oxide layer and the     

Hysteresis in current transport in a GaAs diode containing self-assembled InAs quantum dots

We have observed hysteresis loops in current transport in a GaAs metal–semiconductor–metal diode containing InAs quantum dots. The dots in our structure are directly embedded under the GaAs–metal interface. The charging and discharging of electrons in the dots modulate the current and produce hysteresis. These processes are controlled by the applied voltages. The dots are charged by forward current flowing through the structure. The discharging of the electrons is dominated by the tunneling process under high reverse bias. The modulated currents are well fitted with an electron-trapping model considering both the ground states and the excited states of the quantum dots. Received: 5 October 2000 / Accepted: 12 December 2000 / Published online: 23 May 2001     

顶发射绿光量子点电致发光器件

采用核壳结构的绿光CdSSe/ZnS量子点成功制备了顶发射绿光量子点器件,并详细研究了它的光电特性。与具有相同结构的底发射器件相比,顶发射器件在亮度、效率、色纯度、光谱的电压稳定性上都得到了显著提高。在相同电压7 V下,尽管底发射具有更大的电流密度,但亮度仅为831 cd/m²,而顶发射器件的亮度则可达到1 350 cd/m²,并且顶发射器件的最高亮度可达到7 112 cd/m²。在效率上,顶发射器件的最大电流效率可达6.54 cd/A,远大于底发射器件的1.89 cd/A。在光谱方面,在底发射器件中出现的红蓝部分的杂光在顶发射器件中完全被抑制,而且顶发射光谱的半高宽显著窄化,具有更高的色纯度。当电压从4 V变化到9 V时,顶发射器件光谱始终保持稳定,色坐标移动仅为（-0.005,-0.001）。结果表明,顶发射结构有利于提高量子点器件的亮度、效率、色纯度以及光谱的电压稳定性。     

Phonon assisted resonant tunneling and its phonons control

We observe a series of sharp resonant features in the tunneling differential conductance of InAs quantum dots. We found that dissipative quantum tunneling has a strong influence on the operation of nanodevices. Because of such tunneling the current–voltage characteristics of tunnel contact created between atomic force microscope tip and a surface of InAs/GaAs quantum dots display many interesting peaks. We found that the number, position, and heights of these peaks are associated with the phonon modes involved. To describe the found effect we use a quasi-classical approximation. There the tunneling current is related to a creation of a dilute instanton–anti-instanton gas. Our experimental data are well described with exactly solvable model where one charged particle is weakly interacting with two promoting phonon modes associated with external medium. We conclude that the characteristics of the tunnel nanoelectronic devices can thus be controlled by a proper choice of phonons existing in materials, which are involved.     

Non-Equilibrium Quantum Transport of Bosons through a Quantum Dot

The quantum dot coupled to reservoirs is known as a typical mesoscopic setup to manifest the quantum characteristics of particles in transport. In analogue to many efforts made on the study of electronic quantum dots in the past decades, we study the transport of bosons through such a device. We first generalize the formula which relates the current to the local properties of dot in the bosonic situation. Then, as an illustrative example, we calculate the local density of state and lesser Green function of the localized boson with a bosonic Fano-Anderson model. The current-voltage （I - V） behaviour at zero temperature is presented, and in the bosonic dot it is the I - V curve, in contrast to the differential conductance in the electronic dot, which is found to be proportional to the spectral function.