InxGa1—xAs／AlyGa1—yAs多量子阱的高压光致发光研究

用金刚石对顶砧压力装置在浓氮温度下和０～４ＧＰａ的压力范围内测量了不同阱宽（１．７～１１．０ｎｍ）的ＩｎｘＧａ１－ｘＡｓ／ＡｌｙＧａ１－ｙＡｓ（ｘ，ｙ＝０．１５，０；０．１５，０．３３；０，０．３３）多量子阱的静压光致发光谱，发现在Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ多量子阱中导带第一子带到重空穴第一子带间激子跃迁产生的光致发光峰能量的压力系数随阱宽的增加而减小，在Ｉｎ０．１５Ｇａ０．８５Ａｓ／     

In_xGa_（1－x）As／Al_yGa（1－y）As多量子阱的高压光致发光研究

用金刚石对顶砧压力装置在液氮温度下和０～４ＧＰａ的压力范围内测量了不同阱宽（１．７～１１．０ｎｍ）的ＩｎｘＧａ（１－ｘ）Ａｓ／Ａｌ（１－ｙ）Ｇａ（１－ｙ）Ａｓ（ｘ，ｙ＝０．１５，０；０．１５，０．３３；０，０．３３）多量子阱的静压光致发光谱，发现在Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ多量子阱中导带第一子带到重空穴第一子带间激子跃迁产生的光致发光峰能量的压力系数随阱宽的增加而减小，在Ｉｎ０．１５Ｇａ０．８５Ａｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ和ＧａＡｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ多量子阱中相应发光峰的压力系数随附宽的增加而增加．根据Ｋｒｏｎｉｙ－Ｐｅｎｎｅｙ模型计算了发光峰能量的压力系数随阱宽的变化关系，结果表明导带不连续性随压力的增加（减小）及电子有效质量随压力的增加是压力系数随阱宽增加而减小（增加）的主要原因．     

δ掺杂的赝配HEMTAlGaAs／InGaAs／GaAs结构的光电流谱

本文首次报道了δ掺杂的赝配高电子迁移率晶体管结构（ＨＥＭＴＳ）Ａｌ０．３０Ｇａ０．７０Ａｓ／Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ的光电流谱研究．实验观察到了ｎ＝１重空穴子带到ｎ＝１电子子带和ｎ＝２电子子带的激子吸收峰以及ＧａＡｓ本征吸收相位变化所引起的光电流结构，并对光电流谱随温度和偏压变化的行为进行了讨论．     

AlGaAs／InGaAs／GaAs异质结构中扩散噪声和扩散系数的蒙特卡罗研究

本文用蒙特卡罗法研究了ＡｌＧａＡｓ／ＩｎＧａＡｓ／ＧａＡｓ异质结构中二维电子气的扩散噪声和扩散系数．同ＡｌＧａＡｓ／ＧａＡｓ异质结构的情况一样，平行速度相关函数呈现振荡，但不同的是振幅随电子密度变化很小．另外，振幅在ＩｎＧａＡｓ层厚度增加时下降．用单个电子的相关函数和一组电子的位移方差两种不同方法计算了扩散系数．     

MBE生长InGaAs／GaAs应变层单量子阱激光器结构材料的研究

采用ＶａｒｉａｎＧｅｎⅡＭＢＥ生长系统研究了ＩｎＧａＡｓ／ＧａＡｓ应变层单量子阶（ＳＳＱＷ）激光器结构材料。通过ＭＢＥ生长实验，探索了Ｉｎ＿ｘＧａ＿（１－ｘ）ｔＡｓ／ＧａＡｓＳＳＱＷ激光器发射波长（λ）与Ｉｎ组分（ｘ）和阱宽（Ｌ＿ｚ）的关系，并与理论计算作了比较，两者符合得很好。还研究了材料生长参数对器件性能的影响，主要包括：Ⅴ／Ⅲ束流比，量子阱结构的生长温度Ｔ＿ｇ（ＱＷ），生长速率和掺杂浓度对激光器波长、阈值电流密度、微分量子效率和器件串联电阻的影响。以此为基础，通过优化器件结构和ＭＢＥ生长条件，获得了性能优异的Ｉｎ＿（０．２）Ｇａ＿（０．８）Ａｓ／ＧａＡｓ应变层单量子阱激光器：其次长为９６３ｎｍ，阈值电流密度为１３５Ａ／ｃｍ￣２，微分量子效率为３５．１％。     

InAlGaAs/GaAs量子阱的生长及其界面特性

本文研究了以ＩｎＡｌＧａＡｓ作垒层的ＩｎＡｌＧａＡｓ／ＧａＡｓ量子阱的低压金属有机化合物化学汽相淀积（ＬＰ－ＭＯＣＶＤ）生长及其界面特性,发现在适当生长条件下可以解决ＩｎＧａＡｓ和ＡｌＧａＡｓ在生长温度范围不兼容的问题,得到了高质量的ＩｎＡｌＧａＡｓ／ＧａＡｓ量子阱材料．同时用Ｘ光和低温光致发光（ＰＬ）谱研究了量子阱结构的界面特性,表明适当的界面生长中断不仅可以改善界面平整度,而且能改善垒层ＩｎＡｌＧａＡｓ的质量．     

AlGaAs／InGaAs功率PHEMT用异质材料的计算机优化与器件实验结果

借助一新的工艺模拟与异质器件模型用ＣＡＤ软件──ＰＯＳＥＳ（Ｐｏｉｓｓｏｎ－ＳｃｈｒｏｅｄｉｎｇｅｒＥｑｕａｔｉｏｎＳｏｌｖｅｒ），对以ＡｌＧａＡｓ／ＩｎＧａＡｓ异质结为基础的多种功率ＰＨＥＭＴ异质层结构系统（传统、单层与双层平面掺杂）进行了模拟与比较，确定出优化的双平面掺杂ＡｌＧａＡｓ／ＩｎＧａＡｓ功率ＰＨＥＭＴ异质结构参数，并结合器件几何结构参数的设定进行器件直流与微波特性的计算，用于指导材料生长与器件制造。采用常规的ＨＥＭＴ工艺进行ＡｌＧａＡｓ／ＩｎＧａＡｓ功率ＰＨＥＭＴ的实验研制。对栅长０．８μｍ、总栅宽１．６ｍｍ单胞器件的初步测试结果为：ＩＤｓｓ２５０～４５０ｍＡ／ｍｍ；ｇｍ０２５０～３２０ｍＳ／ｍｍ；Ｖｐ－２．０－２．５Ｖ；ＢＶＤＳ５～１２Ｖ。７ＧＨｚ下可获得最大１．６２Ｗ（功率密度１．０Ｗ／ｍｍ）的功率输出；最大功率附加效率（ＰＡＥ）达４７％。     

InGaAs／InP短时间液相外延层厚度与生长时间的数学拟合

在液相外延（ＬＰＥ）工艺中，采用常规的过冷降温技术，在６４０℃下进行短时间的液相外延ＩｎＧａＡｓ／ＩｎＰ的生长实验，用扫描电镜测量不同生长时间下的外延层厚，对实验曲线进行数学拟合，得到ｄ＝０．２＋０．１３２ｔ０．７５７５的短时间生长厚度与时间的表达式．结果表明，短时间ＬＰＥ生长ＩｎＧａＡｓ／ＩｎＰ和ＩｎＧａＡｓ／ＧａＡｓ相类似，有着相同的初始快速生长阶段．     

浅离子注入InGaAs/InGaAsP SL-MQW激光器的混合蓝移效应

利用３００ｋｅＶ的Ｐ＋离子对ＩｎＧａＡｓ／ＩｎＧａＡｓＰ应变层多量子阱（ＭＱＷ）激光器外延结构实施浅注入,经Ｈ２／Ｎ２混合气氛下的快速退火,结构的光致发光（ＰＬ）峰值波长蓝移了７６ｎｍ,所作宽接触激光器的激射波长蓝移了７７．９ｎｍ．发现具有应变结构的ＩｎＧａＡｓ／ＩｎＧａＡｓＰＭＱＷ,在较低的诱导因素作用下即可产生较大的量子阱混合（ｉｎｔｅｒｍｉｘｉｎｇ）效应     

自组织InAs／GaAs岛状结构生长停顿研究

报道了自组织生长ＩｎＡｓ／ＧａＡｓ岛状结构生长停顿的研究结果．在完成ＩｎＡｓ岛生长以后，引入不同时间的停顿，然后再淀积ＧａＡｓ盖层，将导致ＩｎＡｓ岛光致发光峰蓝移，发光谱线变宽，同时发光强度减弱．透射电子显微镜分析表明在这种结构中出现了失配位错，在其附近应变得到部分弛豫，成为ＩｎＡｓ材料的俘获陷阱．随着停顿时间加长，ＩｎＡｓ岛密度降低，尺寸变小，光致发光谱发生相应变化．     

自组织生长InAs／GaAs量子点的退火效应

通过研究ＧａＡｓ衬底上不同厚度ＩｎＡｓ层光致发光的退火效应，发现它和应变量子阱结构退火效应相类似，ＩｎＡｓ量子点中的应变使退火引起的互扩散加强，量子点发光峰蓝移．量子点中或其附近一旦形成位错，其中的应变得到释放，互扩散现象就不明显了，退火倾向于产生更多的位错，量子点的发光峰位置不变，但强度减弱．     

Annealing behavior of InAs/GaAs quantum dot structures

We investigate the annealing behavior of InAs layers with different thicknesses in a GaAs matrix. The diffusion enhancement by strain, which is well established in strained quantum wells, occurs in InAs/GaAs quantum dots (QDs). A shift of the QD luminescence peak toward higher energies results from this enhanced diffusion. In the case of structures where a significant portion of the strain is relaxed by dislocations, the interdiffusion becomes negligible, and there is a propensity to generate additional dislocations. This results in a decrease of the QD luminescence intensity, and the QD peak energy is weakly affected.     

Study of the Structural and Luminescence Properties of InAs/GaAs Heterostructures with Bi-Doped Potential Barriers

The influence of Bi in GaAs barrier layers on the structural and optical properties of InAs/GaAs quantum-dot heterostructures is studied. By atomic-force microscopy and Raman spectroscopy, it is established that the introduction of Bi into GaAs to a content of up to 5 at % results in a decrease in the density of InAs quantum dots from 1.58 × 10¹⁰ to 0.93 × 10¹⁰ cm^–2. The effect is defined by a decrease in the mismatch between the crystal-lattice parameters at the InAs/GaAsBi heterointerface. In this case, an increase in the height of InAs quantum dots is detected. This increase is apparently due to intensification of the surface diffusion of In during growth at the GaAsBi surface. Analysis of the luminescence properties shows that the doping of GaAs potential barriers with Bi is accompanied by a red shift of the emission peak related to InAs quantum dots and by a decrease in the width of this peak.     

A quantum-dot heterostructure transistor with enhanced maximum drift velocity of electrons

A new type of heterotransistor based on an AlGaAs/GaAs/InAs/GaAs/InAs structure with a layer of InAs quantum dots embedded directly into the GaAs channel is fabricated. High values of the maximum saturation current (up to 35 A/cm) and transconductance (up to 1300 mS/mm) are attained. The specific features of the current-voltage characteristics of the new device are explained in the context of a model that takes into account the ionization of quantum dots in high electric fields and tenfold enhancement of the electron drift velocity in a structure with an InAs quantum-dot layer in the vicinity of an AlGaAs/GaAs heterojunction.     

InAs/GaAs系列量子点研究

为了获得波长长、均匀性好和发光效率高的量子点,采用分子束外延(MBE)技术和S-K应变自组装模式,在GaAs(100)衬底上研究生长了三种InAs量子点。采用MBE配备的RHEED确定了工艺参数:As压维持在1.33×10-5Pa;InAs量子点和In0.2Ga0.8As的生长温度为500℃;565℃生长50nmGaAs覆盖层。生长了垂直耦合量子点(InAs1.8ML/GaAs5nm/InAs1.8ML)、阱内量子点(In0.2Ga0.8As5nm/InAs2.4ML/In0.2Ga0.8As5nm)和柱状岛量子点(InAs分别生长1.9、1.7、1.5ML,停顿20s后,生长间隔层GaAs2nm)。测得对应的室温光致发光(PL)谱峰值波长分别为1.038、1.201、1.087μm,半峰宽为119.6、128.0、72.2nm、相对发光强度为0.034、0.153、0.29。根据PL谱的峰位、半峰宽和相对发光强与量子点波长、均匀性和发光效率的对应关系,可知量子点波长有不同程度的增加、均匀性越来越好、发光效率显著增强。     

利用大周期光子晶体结构增强InAs/GaAs量子点的激发态发光

在该研究中,通过激光全息和湿法腐蚀的方法在InAs/GaAs量子点材料上制备光子晶体,研究了由激光二极管激发制备了光子晶体的InAs / GaAs量子点材料的光致发光光谱.发现具有光子晶体的量子点材料的光谱显示出多峰结构,光子晶体对短波长部分的发光增强和调制比对长波长部分的增强和调制更明显.InAs / GaAs量子点的光致发光光谱通过刻蚀形成的光子晶体结构得到了调控,并且量子点的激发态发光得到了明显增强.     

GaAs基上的InAs量子环制备

在分子束外延系统中,利用3nmGaAs薄盖层将InAs自组装量子点部分覆盖,然后在500°C以及As2气氛中退火一分钟,制成纳米尺度的InAs量子环。这一形成敏感地依赖于退火时的生长条件和生长InAs自组装量子点时的淀积量。InAs在GaAs表面的扩散以及同时发生的In-Ga互混控制着InAs量子环的形成。     

λ=8.3 μm GaAs/AlAs quantum cascade lasers incorporatingInAs monolayers

The development of GaAs-based quantum cascade lasers incorporating indirect bandgap AlAs barriers in conjunction with ultrathin InAs layers in the active regions of the device is reported. The InAs layers produce a downshift of the energies of the lower lasing states, allowing laser emission to be observed at λ=8.34 μm. The GaAs/InAs/AlAs devices operate in pulsed mode up to a maximum temperature of 250 K, with a characteristic temperature of around 200 K for T>100 K     

GaAs-based long-wavelength InAs bilayer quantum dots grown by molecular beam epitaxy

Molecular beam epitaxy growth of a bilayer stacked InAs/GaAs quantum dot structure on a pure GaAs matrix has been systemically investigated.The influence of growth temperature and the InAs deposition of both layers on the optical properties and morphologies of the bilayer quantum dot（BQD） structures is discussed.By optimizing the growth parameters,InAs BQD emission at 1.436μm at room temperature with a narrower FWHM of 27 meV was demonstrated.The density of QDs in the second layer is around 9×10⁹ to 1.4×10¹⁰ cm^-2. The BQD structure provides a useful way to extend the emission wavelength of GaAs-based material for quantum functional devices.     

Localization of holes in an InAs/GaAs quantum-dot molecule

Deep-level transient spectroscopy is used to study the emission of holes from the states of a vertically coupled system of InAs quantum dots in p-n InAs/GaAs heterostructures. This emission was considered in relation to the thickness of a GaAs interlayer between two layers of InAs quantum dots and to the reversebias voltage U_r. It is established that hole localization at one of the quantum dots is observed for a quantum-dot molecule composed of two vertically coupled self-organized quantum dots in an InAS/GaAs heterostructure that has a 20-Å-thick or 40-Å-thick GaAs interlayer between two layers of InAs quantum dots. For a thickness of the GaAs interlayer equal to 100 Å, it is found that the two layers of quantum dots are incompletely coupled, which results in a redistribution of the hole localization between the upper and lower quantum dots as the voltage U_r applied to the structure is varied. The studied structures with vertically coupled quantum dots were grown by molecular-beam epitaxy using self-organization effects.