GaN/AlN量子点结构中的应变分布和压电效应

从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发,采用有限元方法计算了GaN/AlN量子点结构中的应变分布,研究了其自发极化、压电极化以及极化电荷密度.结果表明,应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化,使电子聚集在量子点顶部,空穴聚集在量子点下面的湿润层中,在量子点结构中产生显著的极化电场,并讨论了电场的存在对能带带边的形状以及能级分布的影响.     

GaN／AIN量子点结构中的应变分布和压电效应

从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发，采用有限元方法计算了GaN／AIN量子点结构中的应变分布，研究了其自发极化、压电极化以及极化电荷密度．结果表明，应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化，使电子聚集在量子点顶部，空穴聚集在量子点下面的湿润层中，在量子点结构中产生显著的极化电场，并讨论了电场的存在对能带带边的形状以及能级分布的影响．     

半导体技术

O4712007060630GaN/AlN量子点结构中的应变分布和压电效应/梁双,吕燕伍(北京交通大学物理系)//半导体学报.―2007,28(1).―42～46.从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发,采用有限元方法计算了GaN/AlN量子点结构中的应变分布,研究了其自发极化、压电极化以及极化电荷密度。结果表明,应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化,使电子聚集在量子点顶部,空穴聚集在量子点下面的湿润层中,在量子点结构中产生显著的极化电场,并讨论了电场的存在对能带带边的形状以及能级分布的影响。图4表1…     

耦合GaN/AlxGa1-xN量子点中的激子特性

在有效质量近似下，运用变分方法，考虑到量子点内电子和空穴的三维束缚以及由压电极化和自发极化所引起的内建电场，对圆柱型耦合GaN量子点的光学性质及激子态做了研究。给出了激子结合能Eb、量子点发光波长λ、电子-空穴复合率和量子点高度L^GaN以及势垒层厚度L^AlGaN之间的函数关系。结果表明，量子点高度LG^GaN、势垒层厚度L^AlGaN的增加将导致激子结合能、电子-空穴复合率的降低，耦合量子点发光波长的增加。     

非对称应变纤锌矿AlxGa1-xN/GaN/AlyGa1-yN量子阱中浅杂质态的结合能

本文采用变分法数值计算应变纤锌矿AlxGa1−xN/GaN/AlyGa1−yN量子阱中类氢杂质的基态结合能. 计及由自发极化和压电极化引起的内建电场, 讨论阱宽、杂质位置以及左右垒中Al组分对结合能的影响. 结果表明, 尤其在非对称量子阱即势垒宽度或（和）高度不一样的情形下, 杂质位置和垒高对结合能随阱宽变化关系的影响比垒宽更为明显. 对称或非对称结构中, 结合能随杂质位置的变化形如电子基态波函数的空间分布. 此外, 左垒中Al组分对结合能的影响较右垒更甚.     

光通信用高性能应变层量子阱激光器

把应变引入量子阱，改变Ⅲ－Ⅴ族体化合物半导体材料的能带结构，从而全面改善半导体激光器的性能，出现了通信用新一代高性能应变层量子阱激光器。     

不同形状InN/GaN量子点应变场的有限元分析

量子点中的应变场分布对量子点的力学稳定性、压电性能以及光电性能有着重要的影响。基于有限元方法,并考虑了InN/GaN材料的六方纤锌矿结构特性,分别对透镜形、平顶六角金字塔形和六角金字塔形量子点的应变分布进行了比较,结果表明应变主要集中在浸润层和量子点内,在讨论量子点中电子能级时必须考虑浸润层的影响。量子点内的应变分布及静水应变和双轴应变受几何形状的影响明显。此外还计算了三种形状量子点的总能量,六角金字塔形量子点总能量最小,而透镜形量子点总能量最大,因此六角金字塔形是最稳定的结构,而透镜形是最不稳定的结构。     

预应变InGaN/GaN多量子阱发光特性调控研究

为了减弱InGaN/GaN量子阱内的压电极化场,在蓝紫光InGaN/GaN多量子阱激光器结构中采用了预应变InGaN插入层,通过变温电致发光和高分辨X射线衍射测量研究了预应变插入层对量子阱晶体质量和发光特性的影响。实验结果显示,常温下有预应变层的量子阱电致发光谱积分强度显著提高。模拟计算进一步表明,预应变层对量子阱内压电极化场有调制效果,有利于量子阱中的应力弛豫,可以有效减弱量子限制斯塔克效应,有助于提高量子阱的发光效率。     

耦合GaN/AlxGa1-xN量子点的非线性光学性质

在有效质量和偶极矩近似下,考虑了由于压电极化和自发极化所引起的内建电场和量子点的三维约束效应,对纤锌矿对称Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N圆柱型应变耦合量子点中激子非线性光学性质进行了研究。计算结果表明,内建电场使吸收光谱向低能方向移动,发生红移现象,并且使吸收峰强度大大减小。量子限制效应使光吸收峰强度随着量子点尺寸的减小而增强,并且随着量子点尺寸的减小,吸收光谱发生蓝移现象。     

自组装InGaN/GaN量子点的研究进展

GaN基量子点的生长及其特性已成为目前Ⅲ-Ⅴ族半导体研究的热点.由于其较强的量子效应,量子点结构的光电器件有望获得比量子阱器件更优异的性能.总结了InGaN/GaN量子点的最新研究进展,从生长模式、发光特性和制造工艺三个方面对InGaN/GaN量子点做了较详细的介绍,并对其在半导体器件的具体应用前景上提出了合理的设想.     

A study of carrier statistics in InGaN/Gan LED structures

The carrier statistics in LED structures with ultrathin multilayer InGaN insertions in a GaN matrix was studied. The optical data obtained indicate that an array of quantum dots (QDs) is formed in these structures. The QDs are scattered in size, which leads to an inhomogeneous broadening of the energy spectrum of carriers localized in the QDs. It is shown that, despite the suppressed transport of carriers between QDs, carriers are distributed among the levels of the QD array quasi-statistically at temperatures of about room temperature and higher. This makes it possible to describe the carrier injection and recombination in the device structures studied in terms of quasi-Fermi levels for electrons and holes.     

Characteristic temperature of a tunneling-injection quantum dot laser: Effect of out-tunneling from quantum dots

A laser structure is studied, which exploits tunneling-injection of electrons and holes into quantum dots (QDs) from two separate quantum wells (QWs). An extended theoretical model is developed allowing for out-tunneling leakage of carriers from QDs into the opposite-to-injection-side QWs (electrons into the p-side QW and holes into the n-side QW). Due to out-tunneling leakage, parasitic recombination of electron-hole pairs occurs outside QDs – in the QWs and optical confinement layer. The threshold current density j_th and the characteristic temperature T₀ are shown to be mainly controlled by the recombination in the QWs. Even in the presence of out-tunneling from QDs and recombination outside QDs, a tunneling-injection laser shows potential for significant improvement of temperature stability of j_th – the characteristic temperature T₀ remains very high (above 300 K at room temperature) and not significantly affected by the QD size fluctuations.     

Modulation of a quantum well potential by a quantum-dot array

The possibility of locally varying the potential energy of the electrons and holes localized in a quantum well by a quantum-dot array deposited in the immediate vicinity of the quantum well is demonstrated. These changes in the potential energy are induced when a strain arises in the quantum-dot region. Fiz. Tekh. Poluprovodn. 31, 109–113 (January 1997)     

Non-Markovian gain and luminescence of an InGaN-AlInGaN quantum-well with many-body effects

The optical gain and the luminescence of an InGaN quantum well with quaternary AlInGaN barriers is studied theoretically. We calculated the non-Markovian optical gain and the luminescence for the strained-layer wurtzite quantum well taking into account of many-body effects. It is predicted that both optical gain and luminescence are enhanced significantly when aluminum and indium are introduced into the quaternary barrier composition. Adding the aluminum to the barrier will increase of the confinement potentials for electrons and holes, while the indium will reduce the biaxial strain, which in turn reduces the internal field caused by spontaneous polarization and piezoelectric effects.     

压电扭转问题中非线性极化分析及电场检测

应用弹性理论、压电理论分析了压电体内的应力状态及由其所导致的非线性极化状态。由于极化梯度的存在,不仅在压电体的表面上会产生等效面束缚电荷,在压电体内部同时也会有等效体束缚电荷的聚集。以矩形截面石英柱体为例,选取级数形式的应力函数,采用能量法及根据电场的等效原理推导了由扭转而产生的剪应力和面束缚电荷密度及体束缚电荷密度的解析表达式,得到了迥异于线性极化的结果。采用有限元方法计算了束缚电荷产生的电场。建立了机械扭矩同检测电极的输出电量之间的线性关系,并实现了单压电体扭矩检测。     

Ultrafast Electronic Dynamics in Unipolar n-Doped InGaAs–GaAs Self-Assembled Quantum Dots

The dynamics of electron capture and relaxation in an n-doped quantum-dot (QD) infrared detector structure are studied directly in the time domain using ultrafast intraband-pump-interband-probe differential transmission spectroscopy. Femtosecond midinfrared pulses are used to excite electrons from the doped QDs into the conduction band continuum, and the complete electron distribution functions are monitored as a function of time using an interband probe. Because only electrons are excited and no holes are present, the electron-hole scattering which dominates the relaxation in bipolar systems is not present, and the measurement yields the electron dynamics exclusively. Excitation-dependent electron capture times were measured from 40 to <10 ps with increasing pump intensity. Intradot inter-level relaxation times were observed to be ~100 ps, driven by Auger-type electron-electron scattering. Nanosecond-scale dynamics in the n=1 state were also observed and attributed to transport effects. Our results indicate that the phonon bottleneck in the QDs is circumvented by Auger scattering; nevertheless, the electron dynamics in the unipolar device are found to be slower than those observed in bipolar systems, which confirms the significance of the holes in the carrier relaxation in bipolar devices. The results also support the improved operation of QD infrared photodetectors relative to quantum-well-based devices     

GaN/GaAlN宽量子阱的二类激子特征

考虑了内建电场的影响,用变分法计算了GaN/GaAlN量子阱(QW)的电子子带和激子结合能.结果表明,对于阱宽较大情形,电子和空穴高度局域在QW边沿附近.内建电场造成的电子空穴空间的较大分离使QW激子表现出二类阱特征.重空穴基态结合能对Al浓度变化不敏感.