半导体量子点及其应用(Ⅱ)

理论分析表明，基于三维受限量子点的分离态密度函数的量子器件，以其独特的优异电学、光学性能和极低功耗，在纳米电子学、光电子学，生命科学和量子计算等领域有着极其广泛的应用前景，本文仅就量子点在量子点激光器、量子点红外探测器、单光子光源、单电子器件和量子计算机等方面的应用作一简单的介绍．     

半导体量子点激光器研究进展

首先简要地回顾了半导体激光器发展的历史和量子点激光器所特有的优异性能,进而介绍半导体量子点及其三维量子点阵列的制备技术,然后分别讨论了量子点激光器（能带）结构设计思想,实现基态激射时所必须具备的条件和近年来国内外半导体量子点器的研究进展。最后分析讨论了量子点激光器研制中存在的问题和发展趋势。     

半导体量子点电子结构理论研究的进展

半导体量子点材料由其具有重要的理论研究意义和潜在的巨大应用前景而成为当今理论和材料研究的热点，本文综述了半导体量子点材料电子结构的理论研究发展进程。     

玻璃中的半导体量子点

介绍了玻璃中的半导体量子点。对玻璃中半导体量子点的生长过程、量子的电子态，量子尺寸效应、库仑阻塞效应及介电效应，做了比较全面的介绍。讨论了量子点的应用及发展前景。     

铁电体-半导体量子点复合材料

文章介绍了这一领域的最新研究进展,并重点报道了一类新型铁电体基纳米复合材料－铁电体半 量子点复合材料的制备与光学性质,该材料在新型电致光元件及量子点激器中有着很好的应用前景。     

半导体量子点的形状对受限激子的影响

在有效质量近似范围内,采用有限深势阱模型,考虑介电受限、计入表面极化效应的情况下,研究了球形、立方形半导体量子点的形状对受限激子的影响．结果表明量子点的形状效应不可忽略. 关键词：     

微腔增强发射的半导体量子点单光子源

单光子源是实现量子密匙分配、线性光学量子计算的基本单元。作者回顾了单光子源在量子信息科学发展中的作用,讨论了光子的统计特性,分析了具有类似原子二能级结构的半导体量子点作为单光子发射源的特点,介绍了微腔与二能级系统的耦合以及微腔量子电动力学基本原理。在弱耦合区,Purcell效应导致微腔中量子点激子复合寿命降低,因此可用微腔来改善量子点单光子发射效率。文章总结了近年来在半导体微腔增强量子点单光子发射领域的进展,探讨了分布式布拉格反射微腔、柱状微腔和光子晶体微腔等结构对改善半导体量子点单光子发射和收集效率、光子极化以及光子全同性等方面的作用,并对未来半导体量子点单光子源的发展进行了展望。     

半导体中的自旋弛豫--从体材料到量子阱、量子线、量子点

本文对半导体中的自旋弛豫过程给出一个简要的回顾,介绍了半导体材料从体材料到量子阱、量子线、量子点不同维数的结构中各种自旋弛豫过程,主要关注了自旋去相位和相干控制。对于不同材料中的各种弛豫机制,关注的重点在于如何能够在实验上以一种可以控制的方式来改变可调参数从而达到控制自旋弛豫过程。这些参数主要有电场、磁场、温度、应变、有效g因子等等。本文的组织上,首先介绍研究前景,第1部分简要介绍了自旋弛豫的四种机制。第2部分按照维数的不同将半导体中自旋弛豫分为3个部分:体材料、量子阱、量子线、量子点,在每一部分中又基本上按照电子、空穴、激子的顺序进行了简要的总结:对于不同的载流子,考虑了自旋弛豫对可调参数的依赖关系。这些结果要么试图解释了已有的实验结果,要么从理论上给出预言从而给实验指明了方向,为室温下可以使用的自旋电子学器件设计提供了依据,为固态量子计算和量子信息处理铺平了道路。最后简单地给出展望。     

半导体中的自旋弛豫——从体材料到量子阱、量子线、量子点

本文对半导体中的自旋弛豫过程给出一个简要的回顾,介绍了半导体材料从体材料到量子阱、量子线、量子点不同维数的结构中各种自旋弛豫过程,主要关注了自旋去相位和相干控制。对于不同材料中的各种弛豫机制,关注的重点在于如何能够在实验上以一种可以控制的方式来改变可调参数从而达到控制自旋弛豫过程。这些参数主要有电场、磁场、温度、应变、有效g因子等等。本文的组织上,首先介绍研究前景,第1部分简要介绍了自旋弛豫的四种机制。第2部分按照维数的不同将半导体中自旋弛豫分为3个部分:体材料、量子阱、量子线、量子点,在每一部分中又基本上按照电子、空穴、激子的顺序进行了简要的总结:对于不同的载流子,考虑了自旋弛豫对可调参数的依赖关系。这些结果要么试图解释了已有的实验结果,要么从理论上给出预言从而给实验指明了方向,为室温下可以使用的自旋电子学器件设计提供了依据,为固态量子计算和量子信息处理铺平了道路。最后简单地给出展望。     

半导体量子点中的杂化量子比特

文章介绍了半导体新型量子比特——杂化量子比特。通过与半导体量子点中自旋量子比特和电荷量子比特进行比较,阐述了杂化量子比特兼具长相干与快操控的优点。在总结了杂化量子比特发展与现状的基础上,进一步简单介绍了中国科学技术大学中国科学院量子信息重点实验室在改进型杂化量子比特方面的工作成果。     

半导体微结构物理效应及其应用讲座 第2讲 量子阱、超晶格物理及其在光电子领域中的应用

文章介绍了半导体量子阱、超晶格的基本物理，以及它在光电子领域中的应用，包括量子阱、量子线、量子点、激光器、光调制器、自电光效应器件、量子点器件等．     

Terahertz wave generation in coupled quantum dots

Based on coupled quantum dots,we present an interesting optical effect in a four-level loop coupled system.Both the two upper levels and the two lower levels are designed to be almost degenerate,which induces a considerable dipole moment.The terahertz wave is obtained from the low-frequency component of the photon emission spectrum.The frequency of the terahertz wave can be controlled by tuning the energy levels via designing the nanostructure appropriately or tuning the driving laser field.A terahertz wave with adjustable frequency and considerable intensity(100 times higher than that of the Rayleigh line) can be obtained.It provides an effective scheme for a terahertz source.     

Quantum computation with two-dimensional graphene quantum dots

We study an array of graphene nano sheets that form a two-dimensional S=1/2 Kagome spin lattice used for quantum computation. The edge states of the graphene nano sheets are used to form quantum dots to confine electrons and perform the computation. We propose two schemes of bang-bang control to combat decoherence and realize gate operations on this array of quantum dots. It is shown that both schemes contain a great amount of information for quantum computation. The corresponding gate operations are also proposed.     

Quantum computation with two-dimensional graphene quantum dots

We study an array of graphene nano sheets that form a two-dimensional S=1/2 Kagome spin lattice used for quantum computation.The edge states of the graphene nano sheets are used to form quantum dots to confine electrons and perform the computation.We propose two schemes of bang-bang control to combat decoherence and realize gate operations on this array of quantum dots.It is shown that both schemes contain a great amount of information for quantum computation.The corresponding gate operations are also proposed.     

Exact analytical solutions for shallow impurity states in symmetrical paraboloidal and hemiparaboloidal quantum dots

The problem of a shallow donor impurity located at the centre of a symmetrical paraboloidal quantum dot (SPQD) is solved exactly. The Schrödinger equation is separated in the paraboloidal coordinate system. Three different cases are discussed for the radial-like equations. For a bound donor, the energy is negative and the solutions are described by Whittaker functions. For a non-bound donor, the energy is positive and the solutions become coulomb wave functions. In the last case, the energy is equal to zero and the solutions reduce to Bessel functions. Using the boundary conditions at the dot surfaces, the variations of the donor kinetic and potential energies versus the size of the dot are obtained. The problem of a shallow donor impurity in a Hemiparaboloidal Quantum dot (HPQD) is also studied. It is shown that the wave functions of a HPQD are specific linear combinations of those of a SPQD.     

Visible photoluminescence from Ge quantum dots

Spectroscopic analyses on stacked Ge quantum dots (QDs) on Si (1 0 0) substrates are presented. Strong and visible photoluminescence around 620 nm from stacked Ge QDs is observed. The luminescence is intense and clearly visible to the naked eye at both room temperature and low temperature. We have investigated the temperature dependence of the luminescence, as well as the composition of Ge dots via transmission electron microscopy and the Raman spectroscopy. Possible causes of the visible luminescence are also speculated in this report.     

Polarized emission and excitonic fine structure energies of InGaN quantum dots

The linear polarization of the excitonic emission from quantum dot-like potential minima formed in a thin InGaN layer is investigated. The recorded emission lines exhibit significant intensity linearly polarized along the wurtize c-axis. For many of the studied spectra, the excitonic fine-structures were resolved, revealing energy splittings in the order of ∼200 μeV.