The study of optical properties on InAs self-organized quantum dots

由于半导体量子点具有零维电子特性，它不仅成为基本物理研究的重要对象，也成为研制新一代量子器件的基础。正因如此，量子点材料及器件成为目前国际上最前沿的研究课题之一。GaAs基InAs自组织量子点因其成本低廉、器件工艺成熟，成为替代InP基材料、制备光纤通信用1.3－1.55µm发光激光器的热门材料之一。本文采用分子束外延技术制备了高质量的GaAs基InAs自组织量子点材料。利用原子力显微镜（AFM）、扫描电子显微镜（SEM）、变温及时间分辨的光致发光谱（PL）等手段，分别研究了InGaAs应变层（指在InGaAs层上生长量子点，下同）、InGaAs盖层、InGaAs/InAlAs联合...Quantum dots (QDs), with zero-dimensional electronic properties, have stimulated great interest due to their important roles in fundamental physical research and for developing novel devices. In recent years, it has been one of frontier topics of materials science to study the characterization of self-organized quantum dots and device applications. GaAs-based In(Ga)As self-organized QDs have becom...学位：理学博士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：B20022400

Photoluminescence Characteristics of InAs Self-assembled Quantum Dots in InGaAs/GaAs Quantum Well

在InGaAs/GaAs量子阱中生长了两组InAs量子点样品,用扫描电子显微镜(SEM)测量发现,量子点呈棱状结构,而不是通常的金字塔结构,这是由多层结构的应力传递及InGaAs应变层的各向异性引起的。采用变温光致发光谱(TDPL)和时间分辨谱(TRPL)研究了其光致发光稳态和瞬态特性。研究发现,InGaAs量子阱层可以有效地缓冲InAs量子点中的应变,提高量子点的生长质量,可以在室温下探测到较强的发光峰。在量子阱中生长量子点可以获得室温下1 318 nm的发光,并且使其PL谱的半高宽减小到25 meV。Two types of InAs quantum dots grown in InGaAs/GaAs quantum well(DWELL) were fully investigated by time-resolved(TR) and temperature dependent photoluminescence(TDPL).Scanning electron microscopy(SEM) measurements show that the shape of quantum dots is prismatic,but not the common pyramid shape.We consider that it is attributed to stress transition of multi-layer structure and anisotropy of InGaAs strained layer.DWELL structures could combine both the effects of InGaAs buffer layer and cap layer and even effectively release the stress between the buffer layer and the QDs, which may greatly improve the QDs quality.Strong PL signal emitting at 1 318 nm can be detected at room temperature and the full width at half maximum of PL spectrum is only 25 meV at some temperature.浙江省舟山市科技项目(06110);; 浙江海洋学院人才引进项目(211050041

Photoluminescence of Multilayer InAs Quantum Dots

采用MBE设备生长了多层InAs/GaAs量子点结构,测量了其变温光致发光谱和时间分辨光致发光谱。结果表明多层量子点结构有利于减小发光峰的半高宽,并且可以提高发光峰半高宽和发光寿命的温度稳定性。实验发现,加InGaAs盖层后,量子点发光峰的半高宽进一步减小,最小达到23.6 meV,并且发光峰出现红移。原因可能在于InGaAs盖层减小了InAs岛所受的应力,阻止了In组分的偏析,提高了InAs量子点尺寸分布的均匀性和质量,导致载流子在不同量子点中的迁移效应减弱。Multilayer InAs/GaAs quantum dots structures were grown by molecular-beam epitaxy(MBE).The steady-state and time-resolved photoluminescence of the samples were measured at various temperatures.Results showed that multilayer structures could not only narrow the photoluminescence FWHM(full width at the half maximum) but enhance the stability of the photoluminescence lifetime and FWHM.As for the quantum dots with InGaAs cap layer,the photoluminescent spectra became narrower(the narrowest FWHM was only 23.6meV) and the photoluminescent wavelength became longer.The possible reason for the above phenomena was that the InGaAs cap layer could both release the strains in InAs islands and inhibit segregation of In components,resulting in the weaker migration among different quantum dots

Photoluminescence Characteristics of InAs Self-assembled Quantum Dots Capped with InGaAs and InAlAs Layers

采用变温及时间分辨光致发光谱研究了MBE设备生长的具有不同盖帽层的InAs量子点样品。发现引入InGaAs盖帽层可以使InAs量子点发光的半高宽减小,且向长波长移动。InGaAs/InAlAs联合盖帽层可以进一步改善InAs量子点发光性能,使得室温发光波长超过1.3μm;在10~300 K温度范围内,发光峰值能量及半高宽随温度的变化都较小。随温度升高,InAs量子点的发光寿命首先增大,当温度升高到临界温度TC后,发光寿命逐渐减小。但覆盖不同盖帽层的InAs量子点样品,其发光寿命具有不同的温度关系,联合盖帽层样品具有较大的TC及发光寿命。根据应力及载流子迁移模型对以上实验结果进行了分析。InAs quantum dots(QDs) with different cap layers were fabricated by molecule beam epitaxy(MBE) system.Temperature-dependent and time-resolved photoluminescence(PL) measurements were employed to study PL properties of InAs QDs.InAs QDs with InGaAs cap layer show an obvious diminution of PL emission full width at half maximum(FWHM) and a red-shift of PL peak.InGaAs and InAlAs combination cap layer(CCL) could further improve PL properties of!InAs QDs and lead to above 1.3 μm emission at room temperature.The smallest FWHM of InAs with CCL is only 24 meV around 240 K and the variations of PL FWHM and peak energies are much smaller than those of the others in the temperature range of 10～300 K.As the temperature increases,PL lifetime rises gradually and reaches a maximum value,the critical temperature TC and then drops at higher temperature.However,the detailed lifetime-temperature relations for the samples differ from each other.InAs QDs with CCL have the largest TC and lifetime.A detail analysis is given to explain the experimental results according to the mechanism of stress relaxation and carriers migration.浙江省舟山市科技项目(06110);; 浙江海洋学院科研项目(X06LY01);; 浙江海洋学院人才引进项目(211050041

煤种对含煤球团还原速度的影响

研究了在１２２３￣１４７３Ｋ的氮气氛中３种不同挥发分煤粉的粒度、铁精矿粉粒度、温度及碳－氧摩尔比对含煤球团还原速度的影响。发现降低煤粉或铁精矿粉粒度，提高温度或碳－氧摩尔比可提高含煤球团的还原速度，且这４种因素对还原速度的影响程度随煤种挥发分的降低而增大。分别采用以碳气化反应、气相内扩散、界面反应为控制环节而得出的表达含煤球团反应过程的速度方程处理本研究数据，发现３种速度方程（４种表达形式）均能

煤种对含煤球团还原速度的影响

研究了在１２２３～１４７３Ｋ的氮气氛中３种不同挥发分煤粉的粒度、铁精矿粉粒度、温度及碳—氧摩尔比对含煤球团还原速度的影响。发现降低煤粉或铁精矿粉粒度，提高温度或碳—氧摩尔比可提高含煤球团的还原速度，且这４种因素对还原速度的影响程度随煤种挥发分的降低而增大。分别采用以碳气化反应、气相内扩散、界面反应为控制环节而得出的表达含煤球团反应过程的速度方程处理本研究数据，发现３种速度方程（４种表达形式）均能较好地与本研究数据吻合。比较由不同速度方程计算出的速度常数而得出的含煤球团的活化能，发现对含３种不同挥发分煤的球团，以气相内扩散为控制环节的活化能均较以碳气化反应或界面反应为控制环节的活化能大，由此可推断含煤球团还原过程应由气相内扩散控制。含高挥发分煤的球团的气相内扩散活化能较含低挥发分煤的球团的活化能低，可推断前者的还原速度较快

不同In组分及阱宽的InGaAs/GaAs应变量子阱的表面光伏谱

【中文摘要】 本文采用表面光伏谱方法，对不同组分及阱宽的ＩｎＧａＡｓ／ＧａＡｓ应变量子阱进行了变温表面光伏谱测量．利用形变势模型理论计算，对样品的表面光伏谱进行指认，理论与实验符合得很好． 【英文摘要】 In this Article, Surface photovoltage method has been used to measure the photovoltaic effect of strained InGaAs/GaAs quantum well with different composition of In and width of well at different temperature.The transition peaks of PV spectra were identified compared with the theoretical calculation by the kroig-Penny model . The theoretical calculation results agree with the experiment ones

Studies on Time-resolved Photoluminescence Spectrum of Wetting Layer and Quantum Dots in the Structure of Self-organized Quantum Dots

在GaAs(100)的衬底上,采用MBE自组织方法生长了单层层厚分别为2和2.5 ML,的InAs层。通过原子力显微镜(AFM)观察,证实已在InAs层中形成量子点.采用光致发光谱及时间分辨谱对InAs量子点及浸润层开展研究和对比,分析了单层InAs量子点和浸润层中的载流子迁移过程,较好地解释了实验结果.Single InAs layers (2 and 2.5 ML thick, respectively) were grown on (001) GaAs substrate by molecular-beam epitaxy (MBE). Formation of quantum dots was verified by atomic force microscopy (AFM). We studied and compared InAs quantum dots and wetting layer by photoluminescence and time-resolved spectrum. Migration of carriers among quantum dots and wetting layer were investigated, which explained our results well

自组织生长单层InAs量子点结构中浸润层与量子点发光的时间分辨谱研究

在GaAs(100)的衬底上，采用MBE自组织方法生长了单层层厚分别为2和2．5ML的InAs层。通过原子力显微镜(AFM)观察，证实已在InAs层中形成量子点。采用光致发光谱及时间分辨谱对InAs量子点及浸润层开展研究和对比，分析了单层InAs量子点和浸润层中的载流子迁移过程，较好地解释了实验结果