GaAs/AlxGa1-xAs球形量子点中的电子结构

详细讨论了GaAs/Al_xGa_1-xAs球形量子点内的单电子束缚能级随量子点半径、Al组分以及外电场的变化规律,并计算了考虑量子点内外电子有效质量不同后对电子能级的修正. 另外,用解析和平面波展开两种方法对球形量子点内的电子能级进行了计算,并对计算结果做了比较,发现它们符合的很好. 结论和方法为量子点的研究和应用提供了有益的信息和指导. 关键词： 球形量子点 解析方法 平面波展开方法 有效质量     

有效质量差异和电场对GaN/AlxGa1-xN球形量子点电子结构的影响

用平面波展开法对GaN/Al_xGa_1-xN球形量子点中类氢杂质态能级随量子点半径、Al组分以及结合能随Al组分的变化规律进行了详细讨论.计算了量子点内外有效质量差异对杂质态能级和结合能的修正,结果表明对于Al组分较高的GaN/Al_xGa_1-xN球形量子点,电子有效质量差异对杂质能级和结合能的修正不能忽略.考虑电子有效质量差异后,进一步具体计算了杂质结合能随量子点半 关键词： 球形量子点 平面波展开法 有效质量     

GaAs/AlxGa1-xAs球形量子点中的电子结构

详细讨论了GaAs/AlxGa1-xAs球形量子点内的单电子束缚能级随量子点半径、Al组分以及外电场的变化规律,并计算了考虑量子点内外电子有效质量不同后对电子能级的修正. 另外,用解析和平面波展开两种方法对球形量子点内的电子能级进行了计算,并对计算结果做了比较,发现它们符合的很好. 结论和方法为量子点的研究和应用提供了有益的信息和指导.     

有效质量差异和电场对GaN/AlxGa1-xN球形量子点电子结构的影响

用平面波展开法对GaN/AlxGa1-xN球形量子点中类氢杂质态能级随量子点半径Al组分以及结合能随Al组分的变化规律进行了详细讨论.计算了量子点内外有效质量差异对杂质态能级和结合能的修正,结果表明对于Al组分较高的GaN/AlxGa1-xN球形量子点,电子有效质量差异对杂质能级和结合能的修正不能忽略.考虑电子有效质量差异后,进一步具体计算了杂质结合能随量子点半径、杂质位置以及外电场的变化规律.     

内嵌InAs量子点的δ掺杂GaAs/AlxGa1-xAs二维电子气特性分析

采用分子束外延技术对δ掺杂GaAs/Al_xGa_1-xAs二维电子气(2DEG)样品进行了生长. 在样品生长过程中, 分别改变掺杂浓度(N_d)、空间隔离层厚度(W_d) 和Al_xGa_1-xAs中Al组分(x_Al)的大小, 并在双温(300 K, 78 K)条件下对生长的样品进行了霍尔测量; 结合测试结果, 分别对N_d, W_d及x_Al与GaAs/Al_xGa_1-xAs 2DEG的载流子浓度和迁移率之间的关系规律进行了细致的分析讨论. 生长了包含有低密度InAs量子点层的δ掺杂GaAs/Al_xGa_1-xAs 2DEG 样品, 采用梯度生长法得到了不同密度的InAs量子点. 霍尔测量结果表明, 随着InAs量子点密度的增加, GaAs/Al_xGa_1-xAs 2DEG的迁移率大幅度减小, 实验中获得了密度最低为16×10⁸/cm²的InAs量子点样品. 实验结果为内嵌InAs量子点的δ掺杂GaAs/Al_xGa_1-xAs 2DEG的研究和应用提供了依据和参考. 关键词： 二维电子气 InAs量子点 载流子浓度 迁移率     

纤锌矿GaN/AlxGa1-xN量子阱中极化子能量

采用LLP变分方法研究了纤锌矿GaN/Al_xGa_1-xN量子阱材料中极化子的能级,给出极化子基态能量、第一激发态能量和第一激发态到基态的跃迁能量与量子阱宽度和量子阱深度变化的函数关系。研究结果表明,极化子基态能量、第一激发态能量和跃迁能量随着阱宽L的增大而开始急剧减小,然后缓慢下降,最后接近于体材料GaN中的相应值。基态能量和第一激发态到基态的跃迁能量随着量子阱深度的增加而逐渐增加,窄阱时这一趋势更明显。纤锌矿氮化物量子阱中电子-声子相互作用对能量的贡献比较大,这一值(约40meV)远远大于闪锌矿(GaAs/Al_xGa_1-xAs)量子阱中相应的值(约3meV)。因此讨论GaN/Al_xGa_1-xN量子阱中电子态问题时应考虑电子-声子相互作用。     

InAs/GaAs单量子点中电子/空穴自旋弛豫

利用分子束外延制备了三种类型量子点样品,它们分别是:未掺杂样品、n型Si调制掺杂样品和p型Be调制掺杂样品。在5 K温度下,采用共聚焦显微镜系统,测量了单量子点的光致发光谱和时间分辨光谱, 研究了单量子点中三种类型激子(本征激子、负电荷激子和正电荷激子)的电子/空穴自旋翻转时间。它们的自旋翻转时间常数分别为: 本征激子的自旋翻转时间约16 ns, 正电荷激子中电子的自旋翻转时间约2 ns, 负电荷激子中空穴的自旋翻转时间约50 ps。     

InAs/GaAs和InAs/InxGa1-xAs/GaAs纳米线异质结构的生长研究

利用金辅助金属有机化学气相沉淀法(MOCVD)在GaAs(111)B衬底上分别制备了InAs/GaAs和InAs/In _{x Ga1-xAs/GaAs(0≤x≤1)纳米线异质结构.实验结果显示,直接生长在GaAs纳米线上的InAs纳米线生长方向杂乱或者沿着GaAs纳米线侧壁向衬底方向生长,生长的含有In x Ga1-xAs组分渐变缓冲段的InAs/In x Ga1-x关键词： 纳米线异质结构 xGa1-xAs')" href="#">InxGa1-xAs 组分渐变缓冲层 金属有机化学气相沉淀法}     

GaAs/AlxGa1-xAs量子阱能级结构设计与光谱分析

通过理论计算对用于量子阱红外探测器的GaAs/AlxGa1-xAs量子阱能级结构进行模拟设计,将不同生长结构的量子阱材料的光响应谱和光致荧光谱(PL)与计算结果进行比较.说明量子阱生长结构与量子阱能级结构的关系.欲使量子阱红外探测器的响应峰值在8μm附近,则需量子阱结构中阱宽为47nm,垒中Al含量为029.理论计算与测试结果符合得较好. 关键词：     

AlxGa1-xN/GaN双量子阱的结构和掺杂浓度对子带间跃迁波长和吸收系数的影响

用薛定谔方程和泊松方程自洽计算的方法研究了Al_0.75Ga_0.25N/GaN对称双量子阱(DQWs)中子带间跃迁(ISBT)的波长和吸收系数对中间耦合势垒高度、中间耦合势垒宽度、势阱宽度和势垒掺杂浓度的依赖关系.研究发现,第一奇序子带S_1ood与第二偶序子带S_2even ISBT波长随着中间耦合势垒高度的降低而变短.当中间耦合势垒高度高于0.62 eV时,S_{1odd< 关键词： 自洽 x}Ga_1-xN/GaN双量子阱')" href="#">Al_xGa_1-xN/GaN双量子阱 子带间跃迁     

Spacer layer thickness fluctuation scattering in a modulation-doped AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well

We theoretically study the influence of spacer layer thickness fluctuation（SLTF） on the mobility of a twodimensional electron gas（2DEG） in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer.     

Interband transitions and electronic properties of InAs/GaAs quantum dots embedded in AlxGa1−xAs/GaAs modulation-doped heterostructures

Reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and double-crystal X-ray curves showed that high-quality InAs quantum dot (QD) arrays inserted into GaAs barriers were embedded in an Al_0.3Ga_0.7As/GaAs heterostructure. The temperature-dependent photoluminescence (PL) spectra of the InAs/GaAs QDs showed that the exciton peak corresponding interband transition from the ground electronic subband to the ground heavy-hole subband (E₁-HH₁) was dominantly observed and that the peak position and the full width at half maximum corresponding to the interband transitions of the PL spectrum were dependent on the temperature. The activation energy of the electrons confined in the InAs/GaAs QDs was 115 meV. The electronic subband energy and the energy wave function of the Al_0.3Ga_0.7As/GaAs heterostructures were calculated by using a self-consistent method. The electronic subband energies in the InAs/GaAs QDs were calculated by using a three-dimensional spatial plane wave method, and the value of the calculated (E₁-HH₁) transition in the InAs/GaAs QDs was in reasonable agreement with that obtained from the PL measurement.     

Interface-related effects on confined excitons in GaAs/AlxGa1−xAs single quantum wells

Confined excitons in non-abrupt GaAs/Al_xGa_1−xAs single quantum wells are studied. The graded interfaces are described taking into account fluctuations in their thickness a and positioning with respect to the abrupt interface picture. Numerical results for confined (0,0),(1,1) and (0,2) excitons in GaAs/Al_0.3Ga_0.7As quantum wells show that while the interfacial fluctuations produce small changes (<0.5 meV) in the exciton binding energies, the confined exciton energies can be red- or blue-shifted as much as 25 meV for wells with mean width of 50 Å and 2 ML wide interfaces.     

Physical characterization of OMVPE-grown AlxGa1-xAs multi-layer films by means of non-destructive optical reflectometry

A novel Fourier transform technique which was developed by us previously, is applied in this work for non-destructive determination of thickness and refractive index steps of experimental multilayer heteroepitaxial structures. No time consuming least-squares curve-fits are required and theoretically there is no limit on the number of layers which can be analyzed. In order to demonstrate the above method experimentally, multilayer structures of Al_xGa_1-xAs containing up to five layers on GaAs substrates, were grown by organometallic vapour phase epitaxy (OMVPE). For calibration purposes, initial experiments involved the growth of Al_xGa_1-xAs single epilayers on GaAs substrates by the same technique. Layers were grown at five different compositions from x = 0.1 to x = 0.5. Both photoluminescence (at 12 K) and double-crystal X-ray diffraction measurements were undertaken on the single layers in order to establish the composition of the material. The results show excellent correspondence with each other. These results were also compared to secondary ion mass spectrometry data. The agreement between the optical technique developed by us and the other analytical methods was excellent.     

Different temperature dependence of carrier transport properties between AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures

The temperature dependence of carrier transport properties of AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures has been investigated.It is shown that the Hall mobility in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures is higher than that in Al0.25Ga0.75N/GaN heterostructures at temperatures above 500 K,even the mobility in the former is much lower than that in the latter at 300 K.More importantly,the electron sheet density in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures decreases slightly,whereas the electron sheet density in Al0.25Ga0.75N/GaN heterostructures gradually increases with increasing temperature above 500 K.It is believed that an electron depletion layer is formed due to the negative polarization charges at the InyGa1-yN/GaN heterointerface induced by the compressive strain in the InyGa1-yN channel,which e-ectively suppresses the parallel conductivity originating from the thermal excitation in the underlying GaN layer at high temperatures.     

有限元法计算GaN/AlN量子点结构中的电子结构

根据有效质量理论单带模型，采用有限元方法(FEM)计算了GaN/AlN量子点结构中的电子结构，分析了应变和极化对电子结构的影响，计算了不同尺寸的量子点的能级，分析了量子点的大小对电子能级的影响. 结果表明，形变势和压电势提升了电子能级，而且使简并能级分裂. 随着量子点尺寸的增大，量子限制能减小，而压电势能起到更显著的作用，使电子的能级降低，吸收峰发生红移. 关键词： GaN/AlN量子点结构 有效质量理论 电子能级     

Raman response of GaAs/AlAs superlattices with AlxGa1−xAs intralayers

We present a theoretical investigation on the effects induced on the Raman spectra of a binary (001) GaAs/AlAs superlattice by an intentionally deposited ternary Al_xGa_1−xAs intralayer. We investigate how the intralayer chemical composition and position affect the GaAs-like response of the host system.