V形GaAs/AlGaAs量子线结构的微区光致发光谱研究

在室温下用显微光致发光的方法对单根V形GaAs/AlGaAs量子线进行了沿垂直于量子线方向的 空间分辨扫描测试,观察到各种量子结构的光致发光谱随空间位置的变化.在量子线区域附 近观察到来自量子线(QWR)、颈部量子阱(NQWL)和垂直量子阱(VQWL)等各种结构的发光,而 在距离量子线约1μm以远的发光光谱表现出侧面量子阱(SQWL)的发光.对全部发光光谱用高 斯线形进行了拟合,发现QWR和SQWL的发光包含了两个荧光峰,将它们分别归诸为电子到轻 、重空穴的跃迁.拟合后发光强度的空间变化直接确定了与量子线 关键词： V形GaAs/AlGaAs量子线 显微光致发光 空间分辨扫描     

有机多层量子阱的能量转移

采用多源有机分子气相沉积系统制备了不同类型的有机多量子阱结构，利用电化学循环伏安法和吸收光谱、荧光光谱研究了量子阱的类型、光致发光的特性.电化学循环伏安法和吸收光谱的测量结果表明，PBD/8-羟基喹啉铝(Alq₃)有机量子阱为Ⅰ型量子阱结构，NPB/Alq₃和BCP/Alq₃有机量子阱为Ⅱ型量子阱结构.荧光光谱的研究结果表明，PBD/Alq₃和BCP/Alq₃量子阱结构可以实现PBD，BCP向Alq₃能量完全转移，而NPB/Alq₃量子阱结构，NPB和Alq₃之间只是部分能量转移.文中对影响能量转移的因素进行了讨论. 关键词： 有机量子阱 能量转移     

有机量子阱的光学性质

采用多源有机分子气相沉积系统(OMBD)制备了Alq₃，PBD/Alq₃，PBD/Alq₃/PBD单层、双层以及量子阱结构，利用电化学循环伏安法和吸收光谱、荧光光谱研究了量子阱的类型和样品的光致发光特性.电化学循环伏安法和吸收光谱的测量结果表明，PBD/Alq₃有机量子阱为Ⅰ型量子阱结构.荧光光谱的研究结果表明，单层Alq₃的光致发光峰不随Alq₃厚度变化而变化；但是双层PBD/Alq₃结构光致发光峰随Alq₃厚度的减小而发生蓝移；同样对于PBD/Alq₃/PBD量子阱结构光致发光峰随Alq₃厚度的减小而发生蓝移.对引起光谱蓝移的原因进行了讨论. 关键词： 有机量子阱 光谱蓝移     

聚焦Ga~ 离子束注入方法研制半导体量子线结构

采用聚焦Ga~ 离子束注入方法,在GaAs/Al_(0.3)Ga_(0.7)As多量子阱材料上尝试制备半导体量子线。通过低温光致发光谱,测量了量子线的光电特性,并观察了由于沟道效应导致的深层量子阱的光谱蓝移。     

氧化处理的蓝宝石基片上沉积的ZnO/MgO多量子阱的结构及光学性质研究

采用射频反应磁控溅射的方法,在经过氧化处理的Al₂O₃（0001）基片上制备了具有良好调制结构的ZnO/MgO多层膜量子阱.利用X射线反射率测量、X射线衍射分析、电子探针显微分析、原子力显微镜、透射光谱以及光致发光光谱等表征技术,研究了ZnO/MgO多量子阱的结构、表面形貌和光致发光等特性.XRD以及扫描的结果表明多层膜样品具有高c轴择优取向并且与蓝宝石基片有良好的外延关系.通过X射线反射率测量的结果得到多量子阱的调制周期,结合电子 关键词： ZnO/MgO 多量子阱 反应磁控溅射 变温光谱     

应力导致InAs/In0.15Ga0.85As量子点结构中In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术，在In_0.15Ga_0.85As/GaAs量子阱生长了两个InAs/In_0.15Ga_0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In_0.15Ga_0.85As阱层的厚度和生长温度，获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果，发现该样品量子点的光学性质也同时得到 关键词： 合金分解效应 0.15Ga_0.85As量子点')" href="#">InAs/In_0.15Ga_0.85As量子点 光致发光光谱 压电调制光谱     

蓝光激光器结构中InGaN/GaN多量子阱界面效应的精细光致发光光谱研究

金属有机化学气相沉积（MOCVD）方法制备InGaN/GaN多量子阱结构时,在GaN势垒层生长的N₂载气中引入适量H₂,能够有效改善阱/垒界面质量从而提升发光效率。本工作利用光致发光（PL）光谱技术,对蓝光激光器结构中的InGaN/GaN多量子阱的发光性能进行了精细的光谱学测量与表征,研究了通H₂生长对量子阱界面的调控效应及其发光效率提升的物理机制。室温PL光谱结果显示,GaN势垒层生长载气中引入2.5%的H₂使InGaN/GaN多量子阱的发光效率提升了75%、发光峰的峰位蓝移了17 meV、半峰宽（FWHM）减小了10 meV。通过功率依赖的PL光谱特征分析,我们对InGaN/GaN量子阱中的量子限制Stark效应（QCSE）和能带填充（Band Filling）效应进行了清晰的辨析,发现了发光峰峰位和峰宽的光谱特征主要受QCSE效应影响,H₂的引入能够大幅度降低QCSE效应,并且确定了QCSE效应被完全屏蔽情况下的发光峰能量为2.75 eV。温度依赖的PL光谱数据揭示了通H₂生长量子阱结构中显著减弱的载流子局域化行为,显示界面质量提高有效降低了限制势垒的能量波动,从而导致更窄的发光峰半峰宽。PL光谱强度随温度的变化规律表明,通H₂生长并不改变量子阱界面处的非辐射复合中心的物理本质,却能够显著减少非辐射复合中心的密度,有助于提升量子阱的发光效率。通过时间分辨PL光谱分析,发现通H₂生长会导致量子阱结构中更短的载流子辐射复合寿命,但不影响非辐射复合寿命。载流子复合寿命的变化特征进一步确认了通H₂生长对量子阱结构中QCSE效应和非辐射复合中心的影响规律。综合所有PL光谱分析结果,我们发现通H₂生长能够提高InGaN/GaN多量子阱的界面质量、显著减弱应力效应（更弱的QCSE效应）、降低限制势垒的能量波动以及减少界面处非辐射复合中心的密度,从而显著提升量子阱的发光效率。该研究工作充分显示了PL光谱技术对半导体量子结构发光性能的精细表征能力,光谱分析结果能够为InGaN/GaN多量子阱生长提供有价值的参考。     

量子限制效应对δ掺杂GaAs/AlAs多量子阱中铍受主态寿命的影响

采用远红外时间分辨光谱,研究了量子限制效应对δ掺杂在GaAs/AlAs多量子阱中铍（Be）受主态寿命的影响.在低温下的远红外吸收谱中,清楚地观察到了三条主要吸收线,它们分别来源于铍受主从基态到它的三个奇宇称激发态的跃迁.实验结果表明：随着量子限制效应的增强,受主激发态寿命而减少,实验测得体材料中Be受主2p激发态的寿命是350 ps,而阱宽10 nm的多量子阱中的寿命是55 ps.量子限制效应对布里渊区折叠声学声子模的影响增强了受主带内空穴与声学声子相互作用,从而加快了受主带内空穴的弛豫过程. 关键词： 量子限制效应 受主态寿命 时间分辨光谱 δ掺杂')" href="#">δ掺杂     

(CdZnTe,ZnSeTe)/ZnTe复合量子阱中激子隧穿过程

设计了(CdZnTe,ZnSeTe)/ZnTe复合量子阱结构,并用吸收光谱、室温光致发光谱和飞秒脉冲抽运-探测方法研究了该复合结构中的激子隧穿过程.分别测量了该结构中CdZnTe/ZnTe量子阱层和ZnSeTe/ZnTe量子阱层中激子衰减时间.观察到从CdZnTe/ZnTe量子阱层向ZnSeTe/ZnTe量子阱层的快速激子隧穿,隧穿时间为5.5ps. 关键词： (CdZnTe ZnSeTe)/ZnTe复合量子阱 激子 隧穿 抽运-探测     

反应磁控溅射ZnO/MgO多量子阱的光致荧光光谱分析

采用反应射频磁控溅射方法，在Si(001)基片上制备了具有高c轴择优取向的ZnO/MgO多量子阱.利用X射线反射、X射线衍射、电子探针，光致荧光光谱等表征技术，研究了ZnO/MgO多量子阱的结构、成份和光致荧光特性.研究结果表明，多量子阱的调制周期在1.85—22.3 nm之间，所制备的多量子阱具有量子限域效应，导致了室温光致荧光峰的蓝移，并观测到了量子隧穿效应引起的荧光效率下降.建立了基于多声子辅助激子复合跃迁理论的室温光致荧光光谱优化拟合方法，通过室温光致荧光光谱拟合发现，ZnO/MgO比ZnO/ZnMgO多量子阱具有更大的峰位蓝移，探讨了导致光致荧光光谱展宽的可能因素. 关键词： ZnO/MgO 多量子阱 磁控溅射 光致荧光 量子限域效应     

Energy sublevels in an Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As quantum wire

We report the successful fabrication of a V-grooveAl_0.5Ga_0.5As/GaAs/Al_0.5Ga_0.5As quantum wire system and the temperature-dependent photoluminescence (PL) measurement. The PL spectra are dominated by four features at 681, 642, 635 and 621 nm attributed to the luminescences from quantum wire, top, vertical and side-wall well regions by micro-PL measurements. By the calculations of the energy structure, discrete states (localized sublevels) in the quantum wire region and continuum states (extended along the side-wall and vertical quantum wells) in side-wall and vertical quantum wells have been obtained in both the conduction and valence bands. The calculated excitation energies explain very well the peak positions and their temperature dependence in the photoluminescence measurements.     

Surface and interface phonon-polaritons in freestanding quantum well wire systems of polar ternary mixed crystals

The surface and interface phonon-polaritons in freestanding rectangular quantum well wire systems consisting of polar ternary mixed crystals are investigated in the modified random-element-isodisplacement model and the Born–Huang approximation, based on the Maxwell's equations with the boundary conditions. The numerical results of the surface and interface phonon-polariton frequencies as functions of the wave-vector, geometric structure, and the composition of the ternary mixed crystals in GaAs/Al_xGa_1−xAs and Zn_xCd_1−xSe/ZnSe quantum well wire systems are obtained and discussed. It is shown that there are 10 and 8 branches of surface and interface phonon-polaritons in the two quantum well wire systems respectively. The effects of the “two-mode” and “one-mode” behaviors of the ternary mixed crystals on the surface and interface phonon-polariton modes are shown in the dispersion curves.     

Investigation of blue InGaN light-emitting diodes with step-like quantum well

The concept of a step-like quantum well is proposed with the purpose to reduce the influence of electrostatic field resulting from the piezoelectric effect on the optical performance of blue InGaN light-emitting diodes. Particularly, the optical properties of the LED structures with the In_0.23Ga_0.77N single quantum well, In_0.20Ga_0.80N/In_0.26Ga_0.74N step-like quantum well, and In_0.26Ga_0.74N/In_0.20Ga_0.80N step-like quantum well are numerically investigated in detail. Simulation results show that the In_0.20Ga_0.80N/In_0.26Ga_0.74N step-like-quantum-well LED structure has the best optical performance in virtue of the improvement in spatial overlap of electrons and holes in the quantum well.     

Simultaneous effects of hydrostatic pressure and temperature on the binding energy of hydrogenic impurity in cylindrical quantum well wires

The effect of hydrostatic pressure and temperature on the ground state binding energy of hydrogenic impurities is investigated in a GaAs/Ga_0.7Al_0.3As cylindrical quantum well wire as a function of the wire radius. The calculations are performed using a variational procedure within the effective mass approximation for a finite confinement potential for various values of the hydrostatic pressure and temperatures. The results are compared with the available data in literature and found to be in a good agreement with them.     

Elementary excitations in multiple quantum wire structures

We calculate the plasmon dispersion of electrons in multiple quantum wire structures. Wave function overlapping effects between different wires are neglected. The Coulomb interaction potential is calculated for a model with circular wire area. Analytical results for the excitation spectrum of electron multiple quantum wire structures are obtained within an one-subband model. Landau damping of intrasubband plasmons is discussed. Results for an electron superlattice within a two-subband model are presented and the coupling of intersubband plasmons with intrasubband plasmons is calculated. We compare the theoretical results with recent Raman measurements of intrasubband plasmons in Al _x Ga_1–x As/GaAs wire superlattices. The plasmon dispersion for boson multiple quantum wire structures also is calculated.     

The energy-loss rate via polar-optical phonon scattering in quantum wires

The hot-electron energy-loss rate (ELR) conditioned by confined and interface polar-optical (PO) phonons for a quasi-one-dimensional cylindrical quantum wire embedded in a dielectric medium is investigated analytically. It is shown that the inclusion of the PO-phonon confinement effects is crucial for accurate calculation of the ELR in quantum wire. Taking into account the nonequilibrium phonon populations, the hot-electron ELR is derived by a model, which includes the lowest subband occupation and the phonon confinement effects. The contribution of intersubband transitions to electron ELR for the GaAs quantum wire embedded in Al_xGa_1−xAs is estimated. The extrema on the ELR dependences on electron density are obtained.     

1.55μm InGaAsP/InP应变量子阱激光器的LP－MOCVD生长

本文首次报导了生长温度为550℃,以三甲基镓(TMGa)和三甲基铟(TMIn)为Ⅲ族源,用低压金属有机物气相沉积(LFMOCVD〕技术,高质量1.62um和1.3umInGaAsP及In_0.57Ga_0.43As_0.98P_0.04/In_0.73Ga_0.27As_0.6P_0.4量子阶结构的生长,并给出了1.55umGaAsP/InP分别限制应变量子阱结构激光器的生长条件,激光器于室温下脉冲激射,其阈值电流密度为2.4kA/cm².     

Electron energy spectra in an elliptic quantum wire and elliptic nanotube

In the effective mass approximation, the electron spectra in an elliptic quantum wire and elliptic semiconductor nanotube are investigated. An exact electron energy spectrum in the GaAs elliptic quantum wire and elliptic semiconductor nanotube with impenetrable walls is obtained and an approximate solution of the Schrödinger equation is derived for a finite potential barrier height in the GaAs/Al _x Ga _1?x As elliptic quantum wire. It is demonstrated that the ellipticity of the quantum wire and nanotube results in removal of degeneration of the quasiparticle energy spectrum. Dependences of energies of even and odd states on the ratio of the ellipse semiaxes are nonmonotonic in character. In the limiting case of degeneration of elliptic quantum wires and nanotubes into circular ones, the quasi-particle energy spectrum coincides with the corresponding spectrum in cylindrical nanosystems.     

Optical properties of GaAs/Ga 1-xAlxAs ridge quantum wire: Third-harmonic generation

In this paper, the third-harmonic generation (THG) in GaAs/Ga_1 ? xAl_xAs ridge quantum wires is studied in detail. An analytic expression for the THG is obtained using a compact density matrix approach and an iterative procedure. Numerical calculations are performed for the typical GaAs/Ga_1 ? xAl_xAs ridge quantum wire. The results show that the maximum THG over 10^? 9_? m²_?/V²_? can be obtained. Another important point is that the structural parameters have great influence on the THG in this system.     

Barrier height effect on binding energies of shallow hydrogenic impurities in coaxial GaAs/ AlxGa1−xAs quantum well wires under a uniform magnetic field

The ground state binding energies of axial hydrogenic impurities in a coaxial cylindrical quantum well wire are reported as a function of the barrier height and the radius of wire in the presence of a uniform magnetic field applied parallel to the wire axis. The quantum well wire (QWW) is assumed to be an infinitely long cylinder of GaAs material surrounded by Al_xGa_1−xAs (for finite case and vacuum for infinite case). Binding energy calculations were performed with the use of a variational procedure in the effective mass approximation. We observed that the binding energy is sensitive to well radius only for both larger R$R$ values and small magnetic fields. We also compared the infinite and finite case binding energies and showed that increasing the Al concentration in the finite barrier case, binding energies are increased as expected. Our results are in good agreement and complementary with the previous theoretical works.