闪锌矿InχGal-χ N/GaN量子点的光学特性

在有效质量近似下,通过变分方法研究了束缚于闪锌矿InGaN/GaN量子点中的激子态。详细研究了振子强度和发光波长随InGaN/GaN量子点结构参数和量子点内In含量的变化关系。数据结果表明:量子点结构参数和In含量对闪锌矿InGaN/GaN量子点的振子强度和发光波长有重要的影响;激子效应使量子点发光波长红移。     

闪锌矿InχGal-χ N/GaN量子点的光学特性

在有效质量近似下,通过变分方法研究了束缚于闪锌矿InGaN/GaN量子点中的激子态.详细研究了振子强度和发光波长随InGaN/GaN量子点结构参数和量子点内In含量的变化关系.数据结果表明:量子点结构参数和In含量对闪锌矿InGaN/GaN量子点的振子强度和发光波长有重要的影响;激子效应使量子点发光波长红移.     

Al含量对闪锌矿GaN/AlxGa1-xN量子点光学性质的影响

利用有效质量近似和变分原理,考虑量子点的3维约束效应,研究了圆柱形闪锌矿GaN/AlxGa1-xN量子点的光学特性随势垒层Al含量的变化关系问题。结果表明,势垒层Al含量对量子点的发光波长、振子强度和激子结合能有重要的影响,激子效应对量子点发光波长的影响很大。     

闪锌矿GaN/Al0.15Ga0.85N量子点的光学特性

在有效质量近似条件下,利用变分法计算了量子点高度对GaN/AlGaN量子点光学性质的影响。研究了激子结合能、量子点发光波长、电子-空穴复合率随量子点高度的变化关系。数据结果表明量子点高度对激子结合能、量子点发光波长、电子-空穴复合率有着重要的影响,激子效应将使量子点发光波长红移。     

半导体量子点发光特性研究

目的：研究影响半导体量子点发光的主要因素及影响机制。方法：采用激子模型对半导体量子点的发光特性进行了研究。结果：得到了量子点的激子能级随外界条件的变化情况。结论：量子点所处的外部环境会不同程度的影响其发光特性,因此量子点的发光特性还有待进一步研究。     

应变纤锌矿GaN/AlxGa1-xN柱形量子点中子带光吸收及其压力效应

在有效质量近似下,研究了应变纤锌矿GaN/AlxGa1-xN柱形量子点中基态与第一激发态波函数、能级和导带内的子带光吸收及其压力效应,数值计算了光吸收系数随量子点尺寸、组分和光照强度的变化,讨论了流体静压力对光吸收的影响.结果表明:随着量子点尺寸的减小和组分的增加子带跃迁吸收峰升高且发生蓝移;GaN/AlxGa1-xN量子点子带跃迁产生的吸收峰值会随流体静压力的减小而增加且发生红移.     

InAs/GaAs量子点生长中应力分析

围绕InAs（InGaAs）/GaA叠层量子点电池的制作,本文通过文献研究和对近邻面生长实验研究认为,InAs/GaAs量子点生长形貌和特性受生长环境条件和生长条件影响。其中,客观、不可改变的外延层与衬底晶格常数、生长台面、超晶格结构等环境条件对量子点生长最为重要。这些环境条件通过生长应力,决定了量子点生长中的有序成核、生长、合并,直至出现缺陷的多晶体生长,其作用贯穿整个量子点生长过程。     

制备GaN基材料的数值模拟研究进展

综述了紫外探测器的实际应用,特别介绍了紫外预警系统的作用原理;详细介绍了GaN基材料及其生长方法;对MOCVD法制备GaN基材料的过程做了详细描述,特别介绍了国内外MOCVD系统制备GaN基材料的数值模拟方法。     

一种量子阱结构发光器件的模拟与分析

基于Slivaco公司的TCAD软件构建一种新型量子点发光器件,以GaN基底作为电流传输层,在InGaN量子阱中植入InN量子点,并对该器件的电致发光特性进行了仿真.得到了该器件的伏安特性曲线、电致发光光谱曲线,以及量子点尺寸对其发光光谱的影响.仿真结果表明,在外加电压超过3.2V时,发光层的电子和空穴会产生强烈的复合发光;从0.1~2nm改变量子点的尺寸,发射峰从461nm移至481nm,红移了20nm,从2~10nm改变量子点尺寸,光谱基本没有变化.     

类氢杂质对InxGa1-xN/GaN和GaN/AlxGa1-xN量子点中束缚激子态的影响

在考虑内建电场效应和量子点(QD)的三维约束效应的情况下,运用变分方法研究了类氢施主杂质的位置对Ⅲ族氮化物量子点中束缚激子态的影响.结果表明:当类氢施主杂质位于量子点中心,InxGa1-xN/GaN量子点的高度和In含量大于临界值时,约束在QD中激子的基态能降低,激子态的稳定性增强,在较高的温度下观察到半导体量子点吸收谱中的激子峰,发光波长增大.而类氢施主杂质总是使束缚在GaN/AlxGa1-xN量子点中激子的基态能降低,杂质可能使在更高温度下观察到GaN/AlxGa1-xN量子点中的激子,发光波长增大.研究发现类氢施主杂质位于量子点上界面时,激子的基态能最小,系统最稳定;随着施主杂质下移,激子基态能增加,激子的解离温度下降,发光波长减小.     

拓扑绝缘体量子点中的磁交换相互作用

从理论上研究了拓扑绝缘体量子点中的磁交换相互作用.在拓扑绝缘体量子点中,边缘态电子数可以通过量子点的尺寸和外加电场进行调控.当量子点中掺入单个磁离子并且边缘态填充奇数电子时,电子与单个磁离子之间的交换相互作用达到最大值;而边缘态填充偶数电子时,电子与单个磁离子之间的交换相互作用消失.当量子点中掺入2个磁离子时,电子与Mn离子的sp-d相互作用会出现奇偶振荡行为,Mn离子间的相互作用取决于Mn离子间距和量子点壳层中的电子数,表现出典型的Ruderman-Kittel-Kasuya-Yosida型间接交换机制.工作澄清了拓扑绝缘体量子点壳层结构对其磁性的影响,有助于人们设计基于拓扑绝缘体量子点的自旋电子学或量子信息器件.     

Controlling cavity reflectivity with a single quantum dot

Solid-state cavity quantum electrodynamics (QED) systems offer a robust and scalable platform for quantum optics experiments and the development of quantum information processing devices. In particular, systems based on photonic crystal nanocavities and semiconductor quantum dots have seen rapid progress. Recent experiments have allowed the observation of weak and strong coupling regimes of interaction between the photonic crystal cavity and a single quantum dot in photoluminescence. In the weak coupling regime, the quantum dot radiative lifetime is modified; in the strong coupling regime, the coupled quantum dot also modifies the cavity spectrum. Several proposals for scalable quantum information networks and quantum computation rely on direct probing of the cavity-quantum dot coupling, by means of resonant light scattering from strongly or weakly coupled quantum dots. Such experiments have recently been performed in atomic systems and superconducting circuit QED systems, but not in solid-state quantum dot-cavity QED systems. Here we present experimental evidence that this interaction can be probed in solid-state systems, and show that, as expected from theory, the quantum dot strongly modifies the cavity transmission and reflection spectra. We show that when the quantum dot is coupled to the cavity, photons that are resonant with its transition are prohibited from entering the cavity. We observe this effect as the quantum dot is tuned through the cavity and the coupling strength between them changes. At high intensity of the probe beam, we observe rapid saturation of the transmission dip. These measurements provide both a method for probing the cavity-quantum dot system and a step towards the realization of quantum devices based on coherent light scattering and large optical nonlinearities from quantum dots in photonic crystal cavities.     

量子点层厚度对量子点发光二极管发光特性的影响简

采用湿法旋涂技术制备量子点发光二极管器件（QD-LEDs）。PEDOT作为空穴注入层,TFB作为空穴传输层,量子点作为发光层,采用无机二氧化钛（TiO2）作为电子传输层,在相同的工艺条件下调节量子点层旋涂转速（800～1100 r/min）,制备不同厚度的量子点发光二极管发光器件（QD-LEDs）。实验结果表明,当量子点层的旋涂转速为900 r/min时,此时的量子点层厚度为30 nm,所制备的量子点发光二极管器件（QD-LEDs）的发光性能最好,开启电压最低,只有5．5 V。     

Colloidal nanocrystal heterostructures with linear and branched topology

The development of colloidal quantum dots has led to practical applications of quantum confinement, such as in solution-processed solar cells, lasers and as biological labels. Further scientific and technological advances should be achievable if these colloidal quantum systems could be electronically coupled in a general way. For example, this was the case when it became possible to couple solid-state embedded quantum dots into quantum dot molecules. Similarly, the preparation of nanowires with linear alternating compositions--another form of coupled quantum dots--has led to the rapid development of single-nanowire light-emitting diodes and single-electron transistors. Current strategies to connect colloidal quantum dots use organic coupling agents, which suffer from limited control over coupling parameters and over the geometry and complexity of assemblies. Here we demonstrate a general approach for fabricating inorganically coupled colloidal quantum dots and rods, connected epitaxially at branched and linear junctions within single nanocrystals. We achieve control over branching and composition throughout the growth of nanocrystal heterostructures to independently tune the properties of each component and the nature of their interactions. Distinct dots and rods are coupled through potential barriers of tuneable height and width, and arranged in three-dimensional space at well-defined angles and distances. Such control allows investigation of potential applications ranging from quantum information processing to artificial photosynthesis.     

不同掺杂元素对GaN基材料发光性能影响研究进展

由于GaN材料本身具有的极大优越性,如大禁带宽度、高临界场强、高热导率、高载流子饱和速率、高异质结界面二维电子气浓度等,决定了GaN基材料及其器件在发光半导体材料领域中的重要地位,而高质量GaN的掺杂制备一直是研究者关注的热点.本文根据近几年国内外对掺杂GaN基材料的研究成果,总结概括了IIA族、过渡族以及稀土族元素对GaN的掺杂,分析讨论了不同掺杂元素对GaN基材料发光性能的影响,并以Mg掺杂GaN为例,对比了各种掺杂技术的优缺点.     

Quantum phase transition in a single-molecule quantum dot

Quantum criticality is the intriguing possibility offered by the laws of quantum mechanics when the wave function of a many-particle physical system is forced to evolve continuously between two distinct, competing ground states. This phenomenon, often related to a zero-temperature magnetic phase transition, is believed to govern many of the fascinating properties of strongly correlated systems such as heavy-fermion compounds or high-temperature superconductors. In contrast to bulk materials with very complex electronic structures, artificial nanoscale devices could offer a new and simpler means of understanding quantum phase transitions. Here we demonstrate this possibility in a single-molecule quantum dot, where a gate voltage induces a crossing of two different types of electron spin state (singlet and triplet) at zero magnetic field. The quantum dot is operated in the Kondo regime, where the electron spin on the quantum dot is partially screened by metallic electrodes. This strong electronic coupling between the quantum dot and the metallic contacts provides the strong electron correlations necessary to observe quantum critical behaviour. The quantum magnetic phase transition between two different Kondo regimes is achieved by tuning gate voltages and is fundamentally different from previously observed Kondo transitions in semiconductor and nanotube quantum dots. Our work may offer new directions in terms of control and tunability for molecular spintronics.     

GaN基高电子迁移率晶体管器件的可靠性及退化机制研究进展

GaN基高电子迁移率晶体管（high electron mobility transistor,HEMT）器件在航天、通讯、雷达、电动汽车等领域具有广泛的应用,近年来成为电力电子器件的研究热点。在实际应用中,GaN基HEMT器件随着使用时间的延长会发生退化甚至失效的情况,器件的可靠性问题仍是进一步提高HEMT器件应用的绊脚石。因此,研究器件的可靠性及退化机制对于进一步优化器件性能具有极其重要的意义。将从影响器件可靠性的几个关键因素如高电场应力、高温存储、高温电场和重离子辐照等进行阐述,主要对近几年文献里报道的几种失效机制及相应的失效现象进行了综述和总结,最后讨论了进一步优化器件可靠性的措施,对进一步提高HEMT器件的应用起促进作用。     

On-demand single-electron transfer between distant quantum dots

Single-electron circuits of the future, consisting of a network of quantum dots, will require a mechanism to transport electrons from one functional part of the circuit to another. For example, in a quantum computer decoherence and circuit complexity can be reduced by separating quantum bit (qubit) manipulation from measurement and by providing a means of transporting electrons between the corresponding parts of the circuit. Highly controlled tunnelling between neighbouring dots has been demonstrated, and our ability to manipulate electrons in single- and double-dot systems is improving rapidly. For distances greater than a few hundred nanometres, neither free propagation nor tunnelling is viable while maintaining confinement of single electrons. Here we show how a single electron may be captured in a surface acoustic wave minimum and transferred from one quantum dot to a second, unoccupied, dot along a long, empty channel. The transfer direction may be reversed and the same electron moved back and forth more than sixty times-a cumulative distance of 0.25 mm-without error. Such on-chip transfer extends communication between quantum dots to a range that may allow the integration of discrete quantum information processing components and devices.