Time—Resolved Photoluminescence Studies of AlInGaN Alloys

We study the two samples of AlInGaN,i.e.,1-μm Gan grown at 1030℃ on the buffer and followed by a 0.6μm-thick epilayer of AlInGaN under the low pressure of 76 Torr and the AlInGaN layer deposited diectly on the buffer layer without the high-temperature GaN layer,by temperature-dependent photoluminescence(PL) spectroscopy and picosecond time-resolved photoluminescence(TRPL) spectroscopy.The TRPL signals of both the samples were fitted well as a stretched exponential decay at all temperatures,indicating significant disorder in the material.We attribute the disorder to nanoscale quantum dots or discs of high indium concentration.Temperature dependence of dispersive exponent β shows that the stretched exponential decay of the two samples comes from dfferent mechanisms.The different depths of the localization potential account for the difference,which is illustrated by the results of temperature dependence of radiative recombination lifetime and PL peak energy.     

具有InAlAs浸润层的InGaAs量子点的制备和特性研究

采用自组装方法生长了一种新型的InGaAs量子点/InAlAs浸润层结构.通过选取合适的In组分 ，使InAlAs浸润层的能级与GaAs势垒相当，从而使浸润层的量子阱特征消失.通过低温光致 发光（PL）谱的测试分析得到InGaAs量子点/InAlAs浸润层在样品中的确切位置.变温PL谱的 研究显示，具有这种结构的量子点发光峰的半高全宽随温度上升出现展宽，这明显区别于普 通InGaAs量子点半高全宽变窄的行为.这是因为采用了InAlAs浸润层后，不仅增强了对InGaA s量子点的限制作用，同时切断了载流子的 关键词： InGaAs量子点 InAlAs浸润层 PL谱     

侧基发光性单体与无机纳米颗粒的组装及其光学性质

发光二极管可广泛应用于计算机、电视以及公共场所大型平板显示器等领域 .其所用的发光材料包括无机材料、有机小分子材料和高分子材料等几类 .作为发光材料要具有高的发光效率,良好的稳定性,以及为了实现全色显示其发光波长要能调节 .发光波长的调节,一般是通过能带的变化来实现 .通常使能带变化的方法有掺杂、改变共轭长度（有机材料） [1－ 4]、和改变颗粒大小（半导体纳米材料） [5, 6]等 .我们在进行无机半导体纳米材料与有机分子材料的组装复合时发现有机发光分子在无机颗粒表面的有序排列也能使发光波长显著变化,这可望成为调…     

自发有序Ga0.5In0.5P合金的静压光致发光研究

在０—７ＧＰａ静压范围内测量了自发有序Ga_0.5In_0.5P合金的室温光致发光谱．三块样品的常压带隙能量分别比无序样品低１１５，９２和４３ｍｅＶ，它们的压力系数也从无序样品的９２ｍｅＶ／ＧＰａ分别减小到７５，８１和８３ｍｅＶ／ＧＰａ．用Γ-Ｌ相互作用模型可以同时解释有序合金的带隙能量的降低以及压力系数的减小．得到的Γ-Ｌ相互作用势分别为０.１９，０.１５和０.１０ｅＶ．表明在自发有序Ga_0.5In_0.5P合金中存在着的     

Terahertz Quantum Cascade Laser Operating at 2.94THz

The development of quantum cascade laser at 2.94 THz is reported. The laser structure is based on a bound-to-continuum active region and a semi-insulating surface-plasmon waveguide. Lasing is observed up to a heat-sink temperature of 70 K in pulsed mode with light power of 4.75 mW at 10 K and 1 mW at 70 K. A threshold current density of 296.5 A/cm2 and an internal quantum efficiency of 1.57 × 10-2 per cascade period are also observed at 10 K. The characteristic temperature of this laser is extracted to be T0 = 57.5 K.     

Temperature Insensitivity of Optical Properties of InAs/GaAs Quantum Dots due to a Pregrown InGaAs Quantum Well

Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well.     

分子束外延生长ZnSe自组织量子点光、电行为研究

分别应用光致发光、电容-电压和深能级瞬态傅里叶谱技术详细研究ZnSe自组织量子点样品的光学和电学行为.光致发光温度关系表明ZnSe量子点的光致发光热猝火过程机理.两步猝火过程的理论较好模拟和解释了相关的实验数据.电容-电压测量表明样品表观载流子积累峰出现的深度(样品表面下约100nm处)大约是ZnSe量子点层的位置.深能级瞬态傅里叶谱获得的ZnSe量子点电子基态能级位置为ZnSe导带下的0.11eV,这与ZnSe量子点光致发光热猝火模型得到的结果一致.     

半导体量子点及其应用(Ⅰ)

量子点，又称“人造原子”，它是纳米科学与技术研究的重要组成部分，由于载流子在半导体量子点中受到三维限制而具有的优异性能，构成了量子器件和电路的基础，在未来的纳米电子学、光电子学，光子、量子计算和生命科学等方面有着重要的应用前景，受到人们广泛重视，文章分为Ⅰ、Ⅱ两个部分：第Ⅰ部分介绍了半导体量子点结构的制备和性质；第Ⅱ部分介绍了量子点器件的可能应用。     

硅的低温电学性质

本文在20°—300°K研究了室温载流子浓度2×10¹²—1×10²⁰cm^-3含硼或磷(砷)Si的电学性质。对一些p-Si样品用弱场横向磁阻法及杂质激活能法进行了补偿度的测定,并进行了比较。从霍尔系数与温度关系的分析指出,对于较纯样品,硼受主能级的电离能为0.045eV,磷施主能级为0.045eV,在载流子浓度为10¹⁸—10¹⁹cm^-3时发现了费米简并,对载流子浓度为2×10¹⁷—1×10¹⁸cm^-3的p-Si及5×10¹⁷—4×10¹⁸cm^-3的n-Si观察到了杂质电导行为。从霍尔系数与电导率计算了非本征的霍尔迁移率。在100°—300°K间,晶格散射迁移率μ满足关系式AT^-a,其中A=2.1×10⁹,α=2.7(对空穴);或A=1.2×10⁸,α=2.0(对电子)。另外,根据我们的材料(载流子浓度在5×10¹¹—5×10²⁰cm^-3间),分别建立了一条电阻率与载流子浓度及电阻率与迁移率的关系曲线,以提供制备材料时参考之用。     

Ordered InAs Quantum Dots with Controllable Periods Grown on Stripe-Patterned GaAs Substrates

GaAs （001） substrates are patterned by electron beam lithography and wet chemical etching to control the nucleation of lnAs quantum dots （QDs）. InAs dots are grown on the stripe-patterned substrates by solid source molecular beam epitaxy. A thick buffer layer is deposited on the strip pattern before the deposition of InAs. To enhance the surface diffusion length of the In atoms, InAs is deposited with low growth rate and low As pressure. The AFM images show that distinct one-dimensionally ordered InAs QDs with homogeneous size distribution are created, and the QDs preferentiMly nucleate along the trench. With the increasing amount of deposited InAs and the spacing of the trenches, a number of QDs are formed beside the trenches. The distribution of additional QDs is long-range ordered, always along the trenchs rather than across the spacing regions.