纤锌矿InxGa1-xN／GaN量子阱中的界面声子-电子相互作用

在介电连续模型下,运用传递矩阵的方法研究了任意层纤锌矿量子阱中界面光学声子的电声相互作用,得出了任意层纤锌矿量子阱中界面光学声子与电子相互作用的哈密顿。结果表明,在对称单量子阱GaN／InxGa1-xN／GaN中,界面声子-电子相互作用的耦合强度随组分x的变化差别很大;在对称单量子阱GaN／In0.8Ga0.2N／GaN中,不同的界面声子随着波数的变化对电声相互作用的贡献不同。     

GaN/AlN量子阱中的准受限声子

采用基于宏观介电连续模型的传递矩阵方法研究了任意层纤锌矿量子阱中的准受限声子，得出了任意层纤锌矿量子阱中的准受限声子的本征模解、色散关系；对GaN／A1N单量子阱和耦合量子阱中的准受限声子的色散关系进行了数值计算和讨论。实验发现在阱内的受限行为导致了波矢qe,j的量子化，并且准受限声子的色散随量子阶数m的减小而增强，由色散曲线组成的带随m的增加而变窄。     

纤锌矿InxGal-xN/GaN量子阱中的界面声子-电子相互作用

在介电连续模型下,运用传递矩阵的方法研究了任意层纤锌矿量子阱中界面光学声子的电声相互作用,得出了任意层纤锌矿量子阱中界面光学声子与电子相互作用的哈密顿.结果表明,在对称单量子阱GaN/InxGal-xN/GaN中,界面声子-电子相互作用的耦合强度随组分x的变化差别很大;在对称单量子阱GaN/In0.8Ga0.2N/GaN中,不同的界面声子随着波数的变化对电声相互作用的贡献不同.     

纤锌矿GaN/ZnO量子阱中的界面声子

根据介电连续模型和单轴晶体模型,运用传递矩阵的方法研究了纤锌矿量子阱中的界面声子,并且计算和讨论了纤锌矿GaN/ZnO单量子阱和耦合量子阱中的界面声子的色散关系.计算结果表明纤锌矿晶体的各向异性对界面声子模有大的影响:界面声子模出现在两个能量区域中,分别是:[停琓Zno,鵽,TGaN]和[停琇Zno,鵽,TGaN];界面声子随波数q⊥的减小色散越发明显、随波数q⊥增大分别趋近于54.32 meV和86.56 meV两个定值;当波数q⊥值非常小时,出现界面声子的色散消失现象,消失部分将穿越界面声子的能量区域转化为准受限声子或半空间声子.     

纤锌矿准一维GaN/AlxGa1-xN量子阱线中的极化准受限光学声子模

基于介电连续模型与Loudon的单轴晶体模型,推导分析了纤锌矿准一维量子阱线中的准受限(QC)光学声子模及相应的电子-QC光学声子之间的相互作用函数.对一个AlN/GaN/AlN纤锌矿量子阱线进行了数值计算.结果显示,当体系的角量子数m与z方向上的自由波数kz较小时,QC光学声子模的色散相当明显.观察到纤锌矿量子体系中的QC光学声子模的"退化"行为.通过电子-QC光学声子之间的耦合函数的讨论发现,高频区中的低频支QC模在电子-QC光学声子模之间的相互作用中起主要作用.计算结果还证明自由波数kz与角量子数m对电子-QC光学声子模间的耦合特性具有相似的影响.     

Polar Quasi-Confined Optical Phonon Modes in Wurtzite Quasi-One-Dimensional GaN/AlxGa1-xN Quantum Well Wires

基于介电连续模型与Loudon的单轴晶体模型,推导分析了纤锌矿准一维量子阱线中的准受限(QC)光学声子模及相应的电子-QC光学声子之间的相互作用函数.对一个AlN/GaN/AlN纤锌矿量子阱线进行了数值计算.结果显示,当体系的角量子数m与z方向上的自由波数kz较小时,QC光学声子模的色散相当明显.观察到纤锌矿量子体系中的QC光学声子模的“退化”行为.通过电子-QC光学声子之间的耦合函数的讨论发现,高频区中的低频支QC模在电子-QC光学声子模之间的相互作用中起主要作用.计算结果还证明自由波数kz与角量子数m对电子-QC光学声子模间的耦合特性具有相似的影响.     

纤锌矿准一维GaN/AlxGa1-xN量子阱线中的极化准受限光学声子模

基于介电连续模型与Loudon的单轴晶体模型,推导分析了纤锌矿准一维量子阱线中的准受限(QC)光学声子模及相应的电子-QC光学声子之间的相互作用函数.对一个AlN/GaN/AlN纤锌矿量子阱线进行了数值计算.结果显示,当体系的角量子数m与z方向上的自由波数kz较小时,QC光学声子模的色散相当明显.观察到纤锌矿量子体系中的QC光学声子模的"退化"行为.通过电子-QC光学声子之间的耦合函数的讨论发现,高频区中的低频支QC模在电子-QC光学声子模之间的相互作用中起主要作用.计算结果还证明自由波数kz与角量子数m对电子-QC光学声子模间的耦合特性具有相似的影响.     

氮化物耦合量子阱中的二次谐波产生极化率:压电与自发极化效应

理论考察了存在强内建电场的纤锌矿GaN/InxGa1-xN耦合量子阱体系的二次谐波产生(SHG)特性,结果发现共振SHG系数达到了10-7m/V的量级,SHG系数对耦合量子阱的结构与掺杂组份呈现非单调的依赖关系.结果还表明,通过选择小尺寸垒宽与大尺寸阱宽的耦合量子阱,并适当降低掺杂组份,可在氮化物耦合量子阱中获得较强的SHG极化率.     

磁场对氮化物抛物量子阱中束缚极化子的影响

采用改进的Lee-Low-Pines中间耦合方法研究了在外磁场作用下纤锌矿氮化物抛物量子阱中极化子能级,给出不同磁场下极化子基态能量、结合能随阱宽L的变化关系以及能量随磁场强度B变化的函数关系。在计算抛物量子阱材料中考虑了纤锌矿GaN和Al0.3Ga0.7N构成的抛物量子阱中材料中准LO和准TO声子模的各向异性以及外磁场对极化子能量的影响。结果表明:纤锌矿氮化物抛物量子阱材料中电子-声子相互作用和外磁场对极化子能级有明显的影响。极化子基态能量、结合能随阱宽的增加而减小,随磁场的增加而增大,电子-声子相互作用使极化子能量降低,并且GaN/Al0.3Ga0.7N抛物量子阱对极化子的束缚程度比GaAs/Al0.3Ga0.7As抛物量子阱强,因此,在GaN/Al0.3Ga0.7N抛物量子阱中束缚于杂质中心处的电子比在GaAs/Al0.3Ga0.7As抛物量子阱中束缚于杂质中心处的电子稳定。     

纤锌矿GaN/AlxGa1-xN量子阱中激子能量

考虑了纤锌矿GaN/Al<,x>Ga<,1-x>N量子阱(QW)材料中空穴带质量和光学声子模的各向异性以及声子频率随波矢变化的效应,采用改进的LLP变分法计算了纤锌矿氮化物QW中激子的基态能量和结合能.给出了激子的基态能量和结合能随着QW宽度和Al组分变化的函数关系,并对闪锌矿和纤锌矿GaN/Al<0.3>Ga<,0....     

Influence of growth temperatures on the quality of InGaAs/GaAs quantum well structure grown on Ge substrate by molecular beam epitaxy

Molecular beam epitaxy growth of an In_xGa_1-xAs/GaAs quantum well（QW） structure（x equals to 0.17 or 0.3） on offcut（100） Ge substrate has been investigated.The samples were characterized by atomic force microscopy,photoluminescence（PL）,and high resolution transmission electron microscopy.High temperature annealing of the Ge substrate is necessary to grow GaAs buffer layer without anti-phase domains.During the subsequent growth of the GaAs buffer layer and an In_xGa_1-xAs/GaAs QW structure,temperature plays a key role. The mechanism by which temperature influences the material quality is discussed.High quality In_xGa_1-x As/GaAs QW structure samples on Ge substrate with high PL intensity,narrow PL linewidth and flat surface morphology have been achieved by optimizing growth temperatures.Our results show promising device applications forⅢ-Ⅴcompound semiconductor materials grown on Ge substrates.     

Electronic band structures and optical gain spectra of strainedwurtzite GaN-AlxGa1-xN quantum-well lasers

The electronic band structures, density-of-states, and optical gain spectra for wurtzite GaN-Al_xGa_1-xN quantum wells are studied theoretically based on the Hamiltonian derived using the k.p method. We investigate the dependence of the optical gain and transparent current density on the well width, barrier height, and strain using a numerical approach with high accuracy. The mole fraction of Al in the barrier material is progressively increased to study the effects of quantum confinement and compressive strain. A higher Al mole fraction in the barrier leads to improvement of the TE optical gain and suppression of the TM optical gain. Furthermore, we demonstrate that a reduction of the well width offers improved modal gain over all radiative current densities. We also predict a transparent current density of 250 A/cm² for the GaN-Al_xGa_1-x N single quantum-well (QW) structure. Our results suggest that a suitable combination of thin well width and large barrier height should be selected in improving the TE optical gain in wurtzite GaN-Al_x Ga_1-xN single QW     

Uniaxial strain effect on the electronic and optical properties ofwurtzite GaN-AlGaN quantum-well lasers

The valence subband structures of uniaxial-strained wurtzite (WZ) GaN-AlGaN quantum wells (QW's) are calculated using multiband effective-mass theory. The optical gain is investigated using a numerical approach in which we account for the subband structure modification and mixing due to the anisotropic strain in the QW plane. We show that the mixing of the HH and LH bases in the uniaxial-strained (0001) GaN-AlGaN QW decouples |X〉 and |Y〉 at the Γ point, giving two topmost subbands, Y1 and X1, which can be more widely separated than the HH1 and LH1 subbands in the biaxial-strained (0001) GaN-AlGaN QW. We resolve the states of the subband dispersion in terms of the |X〉, |Y〉, and |Z〉 bases, and show the compositional variation as a function of the in-plane wavevector. Under uniaxial strain, it is possible to exploit the existence of the preferred symmetry at the valence band maximum and the reduced band-edge density-of-states due to the anisotropic in-plane energy dispersion to achieve lower transparency carrier and current densities and higher differential gain in comparison with a pseudomorphic biaxial-strained QW. We show that, for a QW laser structure with the optical cavity along the x axis, uniaxial compressive strain in the y direction shows greater improvement than the uniaxial tensile strain in the x direction of the same magnitude. Thus, a suitable uniaxial strain could be used to improve the threshold performance of WZ GaN-based QW lasers     

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。     

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％。     

Electrons and phonons in quantum wells

The modulation of electron and polar optical phonon states in an AlGaAs/GaAs/AlGaAs quantum well (QW) with an inserted thin AlAs barrier is considered. The OW width dependence of electron-phonon scattering rates are estimated. The large contribution to the change of the electron subband population, the photovoltaic effect, and the electron mobility in the QW accounts for the resonant intersubband scattering of electrons by interface phonons. The decrease of electron mobility limited by polar optical phonon scattering with increasing carrier concentration in the QW is established. The conditions for the increase of mobility in the QW by inserting the AlAs barrier are found. Fiz. Tekh. Poluprovodn. 33, 1049–1053 (September 1999) This article was published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

In_xGa_(1-x)As/GaAs应变单量子阱结构的静压光致发光研究

在室温和液氮温度下,0-60kbar范围内对In_xGa(1-x)As/GaAs应变单量子阱结构进行了静压光致发光研究.在室温下,量子阱中发光峰随压力的变化是亚线性的,而在液氮温度下是线性的.阱中发光峰的压力系数比GaAs势垒的小约10％左右.发现对应于导带第二子带的发光峰的压力系数略大于第一子带的.此结果与GaAs/Al_xGa_(1-x)As量子阱的情况正好相反.     

Spontaneous Emission and Characteristics of Staggered InGaN Quantum-Well Light-Emitting Diodes

A novel gain media based on staggered InGaN quantum wells (QWs) grown by metal-organic chemical vapor deposition was demonstrated as improved active region for visible light emitters. Fermi's golden rule indicates that InGaN QW with step-function like In content in the well leads to significantly improved radiative recombination rate and optical gain due to increased electron-hole wavefunction overlap, in comparison to that of conventional InGaN QW. Spontaneous emission spectra of both conventional and staggered InGaN QW were calculated based on energy dispersion and transition matrix element obtained by 6-band k middotp formalism for wurtzite semiconductor, taking into account valence-band-states mixing, strain effects, and polarization-induced electric fields. The calculated spectra for the staggered InGaN QW showed enhancement of radiative recombination rate, which is in good agreement with photoluminescence and cathodoluminescence measurements at emission wavelength regime of 425 and 500 nm. Experimental results of light-emitting diode (LED) structures utilizing staggered InGaN QW also show significant improvement in output power. Staggered InGaN QW allows polarization engineering leading to improved luminescence intensity and LED output power as a result of enhanced radiative recombination rate.