InGaAs/GaAs单量子阱PL谱的温度变化特性

采用分子束外延方法制备了InGaAs/GaAs单量子阱,利用自组装的光致荧光探测系统,对其进行了光致荧光谱研究。考察了不同温度下荧光峰波长、峰形的影响。研究结果表明:高温时荧光主要是源于带—带间载流子跃迁,而在低温时则来源于束缚在量子阱中激子的跃迁。     

InGaN/GaN多量子阱热退火的拉曼光谱和荧光光谱

通过拉曼光谱及荧光光谱测量研究了采用低压金属有机化学沉积(MOCVD)方法生长的InGaN／GaN多量子阱高温快速热退火处理对量子阱光学性质的影响。观测到退火后InGaN／GaN量子阱的拉曼光谱E2,A1(LO)模式的峰位置出现了红移,而且该振动峰的半高宽也有微小变化。温度升高退火效果更明显。退火使量子阱内应力部分消除,同时In,Ga原子扩散出现相分离使拉曼谱表现出变化。在常温和低温下的光荧光谱表明,退火处理的量子阱发光主峰都出现了红移;而且低温退火出现红移,退火温度升高相对低温退火出现蓝移;同时在低温荧光光谱里看到经过退火处理后原发光峰中主峰旁边弱的峰消失了。讨论了退火对多量子阱光学性质的影响。     

MBE生长PbSe/PbSrSe量子阱结构的光致中红外发光的研究

研究了分子束外延技术生长的PbSe/PbSrSe多量子阱结构的中红外光致荧光现象.高分辨率X射线衍射（HRXRD）谱观察到了多量子阱所特有的多级卫星峰,表明量子阱界面陡峭.变温光致荧光谱测量显示量子阱结构对电子空穴有强的限制效应,在相同温度下,量子阱样品的荧光峰峰位相对PbSe体材料有一定的蓝移.发现量子阱样品的荧光强度同温度有关,温度从150 K上升到230 K时,荧光强度逐渐增大,温度继续升高,荧光强度缓慢下降,但在高于室温时,仍能观察到较强的荧光发射,这说明该量子阱结构材料具有应用于室温工作的中红外 关键词： PbSe/PbSrSe多层量子阱（MQWs） 光致中红外荧光 高分辨X射线衍射（HRXRD）     

用MOCVD方法生长的GaAs/GaAsP量子线及其特性

本实验采用普通的光刻和湿法腐蚀技术,将GaAs基片刻蚀成具有W形沟槽样的非平面结构,基片表面为(100)面,沟槽的侧斜面为(111)B面.在此基片上用低压MOCVD设备外延生长了GaAs/GaAsP多层膜,通过扫描电镜和微区拉曼光谱,研究它们的生长特性,发现GaAs和GaAsP的生长速率与基片的晶向及基片上的生长位置有关.根据这一生长特性,选择合适的W形沟道形状,用常规的量子阱外延方式,在W形沟道中央顶部突起的线条状平面上形成宝塔形生长,从而在尖端长出量子线.低温荧光光谱中观察到相应的能量峰,从而证实量子线的存在.     

量子阱结构对含V形坑InGaN/GaN蓝光LED效率衰减的影响

使用MOCVD在图形化Si衬底上生长了含V形坑的InGaN/GaN蓝光LED。通过改变生长温度,生长了禁带宽度稍大的载流子限制阱和禁带宽度稍小的发光阱,研究了两类量子阱组合对含V形坑InG aN/GaN基蓝光LED效率衰减的影响。使用高分辨率X射线衍射仪和LED电致发光测试系统对LED外延结构和LED光电性能进行了表征。结果表明:限制阱靠近n层、发光阱靠近p层的新型量子阱结构,在室温75 A/cm~2时的外量子效率相对于其最高点仅衰减12.7%,明显优于其他量子阱结构的16.3%、16.0%、28.4%效率衰减,且只有这种结构在低温时(T≤150 K)未出现内量子效率随电流增大而剧烈衰减的现象。结果表明,合理的量子阱结构设计能够显著提高电子空穴在含V形坑量子阱中的有效交叠,促进载流子在阱间交互,提高载流子匹配度,抑制电子泄漏,从而减缓效率衰减、提升器件光电性能。     

快速热退火引起的GaAs／AlGaAs双量子阱中铝原子的扩散研究

用分子束外延生长了ＧａＡｓ／ＡｌＧａＡｓ双量子阱激光器结构样品，并对不同温度快速热退火导致量子阱组分无序即阱和垒中三族元素的扩散过程进行了实验和理论研究 。用光荧光技术测量退火样品的ｎ＝１量子阱能级跃迁峰值位置，结果表明退火前后样品量子阱能级位置发生蓝移，蓝移量随温度的提高而增大，对退火过程中ＧａＡｓ／ＡｌＧａＡｓ量子阱中三族元素的扩散过程中进行了理论分析，并与实验结果相比较，获得了不同退火温度下     

不同In含量InGaN/GaN量子阱材料的变温PL谱

通过对不同In含量的InGaN/GaN量子阱材料的变温光致发光(PL)谱进行实验分析,得出样品激活能和PL谱峰值能量随温度变化的S形曲线中拐点温度与In含量的关系。说明对于我们的样品,这种S形曲线并不是来源于量子限制Stark效应(QCSE),而是与量子阱中In团簇有关。对比结果表明,含In量越多的材料其局域的能量越大,由热扰动脱离局域所需要的温度越高。     

InGaAsN量子阱的光致发光谱研究(英文)

我们测量了低N组分的InGaAsN/InGaAs/GaAs量子阱材料的光致发光(PL)谱,测量温度范围从13K到300K。实验结果显示,InGaAsN的PL谱的主峰值的能量位置随温度的变化呈现出反常的S型温度依赖关系。用Varshni经验公式对实验数据进行拟合之后,发现在低温下InGaAsN量子阱中的载流子是处于局域态的。此外,我们还测量了样品在不同的温度、不同的能量位置的瞬态谱,结果进一步证实了:在低温下,InGaAsN的PL谱谱峰主要是局域态激子的复合发光占据主导地位,而且InGaAsN中的载流子局域态主要是由N等电子缺陷造成的涨落势引起的。     

导纳谱研究两类Si基量子阱基态子能级的性质

用导纳谱技术研究了两类Si基量子阱样品基态子能级的性质.基于量子阱中载流子的热激发模型，从导纳谱中得到的激发能值被认为是阱中重空穴基态位置到阱顶的距离.对于SiGe合金和Si形成的组分量子阱，主要研究了退火对重空穴基态子能级的影响.发现样品的退火温度为800℃时，随退火时间延长，激发能增加.对此现象的解释是，由于Si,Ge互扩散，导致界面展宽，量子限制效应降低，重空穴基态位置下降，从而激发能增加.900℃下退火，由于扩散系数增大和应变弛豫加强，激发能值单调下降，量子限制效应引起的变化被掩盖.对于B高浓度超 关键词：     

刻蚀改变InGaN/AIGaN应变多量子阱发光特性

为了分析干法刻蚀对应变多量子阱(SMQWs)发光特性的影响,采用感应耦合等离子体(ICP)刻蚀技术对金属有机物化学气相沉积(MOCVD)生长的InGaN/AlGaN应变多量子阱覆盖层表面刻蚀了约95 nm.通过光致发光(PL)特性表征发现,干法刻蚀后量子阱光致发光强度较未刻蚀量子阱光致发光强度提高了近3倍.干法刻蚀后,量子阱表面呈现高低起伏状形貌,粗糙度提高,出射光在起伏状粗糙形貌表面反复散射,从而逃逸概率增大,有助于光致发光强度增强.理论计算结果得出表面形貌变化引起的量子阱光致发光强度增强因子约为1.3倍.另外,由于所采用的感应耦合等离子体功率较小,刻蚀损伤深度几乎不会达到量子阱阱层,然而干法刻蚀过程中Ar离子隧穿到量子阱阱层内部可能形成新的发光中心,从而使量子阱的发光强度得到提高.     

刻蚀改变InGaN/AlGaN应变多量子阱发光特性

为了分析干法刻蚀对应变多量子阱(SMQWs)发光特性的影响,采用感应耦合等离子体(ICP)刻蚀技术对金属有机物化学气相沉积(MOCVD)生长的InGaN/AIGaN应变多量子阱覆盖层表面刻蚀了约95 nm。通过光致发光(PL)特性表征发现,干法刻蚀后量子阱光致发光强度较未刻蚀量子阱光致发光强度提高了近3倍。干法刻蚀后,量子阱表面呈现高低起伏状形貌,粗糙度提高,出射光在起伏状粗糙形貌表面反复散射,从而逃逸概率增大,有助于光致发光强度增强。理论计算结果得出表面形貌变化引起的量子阱光致发光强度增强因子约为1．3倍。另外,由于所采用的感应耦合等离子体功率较小,刻蚀损伤深度几乎不会达到量子阱阱层,然而干法刻蚀过程中Ar离子隧穿到量子阱阱层内部可能形成新的发光中心,从而使量子阱的发光强度得到提高。     

Optical properties of GaN/AlN multiple quantum wells

Optical properties of GaN/AlN multiple quantum wells (MQW) have been investigated by Raman scattering, photoluminescence and photoluminescence excitation measurements. A careful examination of the Raman spectrum reveals the fact that the constituent layers of GaN/AlN MQWs are well strained. The experimental results of emission and absorption in MQWs were compared with the calculated solutions of the finite quantum well and the bound states involved in the optical transitions were identified. It is found that the interband transitions up to n=3 bound state can be observed in the strained GaN/AlN MQWs sample. The temperature dependence of the heavy-hole transitions shows an interesting phenomenon, in which the peak energy first increases with increasing temperature and then decreases with the temperature rapidly. The observation can be explained in a consistent way by the strain effects of lattice mismatch due to the interplay between the thermal expansion of GaN and AlN layers. Our results indicate that pseudomorphic GaN/AlN MQWs with good quality can be readily grown, and their applications in optoelectronics can be expected in the near future.     

New method to induce 2D–3D transition of strained CdSe/ZnSe layers

We present new growth conditions for growing high-quality CdSe/ZnSe quantum dots with photoluminescence emission measurable up to room temperature. The surface morphology is characterized in situ by Reflective High Energy Electron Diffraction (RHEED). The key point is the introduction of a new step in the growth process using amorphous selenium to induce a 2D–3D transition of a CdSe strained layer on ZnSe to form the dots. Optical characterizations by photoluminescence of CdSe/ZnSe quantum dots obtained that way, as well as X-ray diffraction results are also discussed here.     

Density controllable growth of ZnO quantum dots by MOCVD

High quality self-assemble ZnO quantum dots (QDs) have been successfully grown on the Si(111) substrates by metalorganic chemical vapor deposition (MOCVD). The diameter of ZnO QDs is about 10 nm in average, and the densities and the sizes of ZnO QDs can be well controlled by adjusting the growth temperature, which were evident in the SEM images. The properties and stress involved in ZnO QDs are studied by X-ray diffraction. In addition, room temperature photoluminescence spectra reveal that the ZnO QDs exhibit a band gap blue shift because of the quantum confinement effects.     

MBE and MOCVD growth and properties of self-assembling quantum dot arrays in III-V semiconductor structures

In this paper, we review our latest developments on the growth and properties of self-assembling quantum dot structures. The self-assembling growth technique which was initially developed using molecular beam epitaxy (MBE), has now been extended to metalorganic chemical vapor deposition (MOCVD). The paper first presents structural results based on atomic force and transmission electron microscopy studies of the quantum dot arrays which were obtained by MBE and MOCVD growth. From the detailed structural analysis we have observed that the formation of coherently strained dots of InAs, InAlAs, and InP dots on various cladding layer surfaces. MBE growth of InAs self-assembled dots has achieved the smallest size distribution, with dots as small as 12nm in diameter. For the MOCVD growth of InP dots we have found that the surface morphology and growth temperature of lower cladding layer growth has a profound influence on island size and density. Recent results on the optical and transport properties of the MBE grown self-assembling dot (SAD) arrays are also presented.     

室温下ZnS-ZnTe应变超晶格的带间跃迁

本文报导了ZnS-ZnTe应变超晶格中的载流子在室温下跃迁复合性质.通过测量室温下光致发光光谱,对载流子在超晶格带间跃迁的过程进行了研究.     

室温下ZnS－ZnTe应变超晶格的带间跃迁

本文报导了ＺｎＳ－ＺｎＴｅ应变超晶格中的载流子在室温下跃迁复合性质．通过测量室温下光致发光光谱，对载流子在超晶格带间跃迁的过程进行了研究．     

InxGa1-xN/InyGa1-yN多量子阱结构 发光特性的测量与分析

利用MOCVD方法在蓝宝石衬底上生长了In_xGa_1-xN/In_yGa_1-yN多量子阱结构外延层,并用变温光致发光(PL)光谱、选择激发光谱以及激发(PLE)光谱等手段研究了该结构的量子效率、多峰效应的起源以及峰位随温度变化等信息。变温PL光谱的结果表明:在温度从30 K变化到300 K时,其峰值强度只下降了1.36倍且发光波长发生了蓝移。通过选择激发光谱证明了其发光峰位的独立性。PLE结果表明了GaN和势垒层的Stokes位移很小,但是In_xGa_1-xN阱层的Stokes位移变化很大。同时,提出了一种可同时获得多个吸收边的数据处理方法。     

Temperature dependent time-resolved exciton luminescence in GaAs/AlGaAs quantum wires and dots

Transient photoluminescence of GaAs/AlGaAs quantum wires and quantum dots formed by strain confinement is studied as a function of temperature. At low temperature, luminescent decay times of the wires and dots correspond to the radiative decay times of localized excitons. The radiative decay time can be either longer or shorter than that of the host quantum well, depending on the size of the wires and dots. For small wires and dots (∼ 100 nm stressor), the exciton radiative recombination rate increases due to lateral confinement. Exciton localization due to the fluctuation of quantum well thickness plays an important role in the temperature dependence of luminescent decay time and exciton transfer in quantum wire and dot structures up to at least ∼ 80 K. Lateral exciton transfer in quantum wire and dot structures formed by laterally patterning quantum wells strongly affects the dynamics of wire and dot luminescence. The relaxation time of hot excitons increases with the depth of strain confinement, but we find no convincing evidence that it is significantly slower in quasi 1-D or 0-D systems than in quantum wells.     

金属有机化学气相外延生长1310nm偏振无关混合应变量子阱半导体光放大器研究

采用低压金属有机化学气相外延设备进行了1.3μm压应变量子阱材料、张应变量子阱材料和混合应变量子阱材料的生长研究.通过x射线双晶衍射和光致发光谱对生长材料进行测试和分析.基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱（4CW3TW）结构有源区，并采用7°斜腔脊型波导结构以有效抑制腔面反射，经蒸镀减反膜后，半导体光放大器光纤光纤小信号增益达21.5dB，在1280—1340nm波长范围内偏振灵敏度小于0.6dB. 关键词： 偏振无关 应变量子阱 半导体光放大器 减反膜