张应变、长波长In_(1-x)Ga_xAs_yP_(1-y)/InP量子阱材料的光荧光谱实验研究

给出了具有二三个量子阱的Ｉｎ１－ｘＧａｘＡｓｙＰ１－ｙ／ＩｎＰ张应变量子阱材料的光荧光谱及ｘ射线双晶衍射摇摆曲线，指出了光荧光峰为量子阱中导带子带和价带子带间本征复合机构所致。理论上分析了光荧光谱中双峰强度比随温度变化的关系，理论计算和实测结果基本一致。     

980 nm应变单量子阱的理论设计

研究了应变单量子阱势阱宽度的计算方法 ,为应变单量子阱的设计提供了理论依据 .对于确定的材料组份 ,根据应变理论及有限深势阱的处理方法 ,系统地计算了 980 nm应变单量子阱宽度 ,理论计算与实验结果相吻合     

张应变,长波长In1—xGaxAsyP2—y／InP量子阱材料的光荧光谱实验室

给出了具有二三个量是的Ｉｎ１－ｘＧａｘＡｓｙＰ１－ｙ／ＩｎＰ张应变量子阱材料的光荧光谱及ｘ射线双晶衍射摇摆曲线，指出了荧光峰为量子阱中导带子带和阶带子带间本征复合机构所致。理论上分析了光荧光谱中双峰强度比随温度变化的关系，理论计算和实测结果基本一致。     

快速热退火提高应变InAs／InP量子阱结构的晶体质量

研究了快速热退火对应变ＩｎＡｓ／ＩｎＰ单晶子阱结构光学性质的影响。样品经最佳条件７００℃，５ｓ的快速热退火，８Ｋ温度下量子阱的荧光强度地加了４倍，量子阱荧光峰仅蓝移１．５ｍｅＶ。     

压应变In_(0.63)Ga_(0.37)As/InP单量子阱的变温光致发光研究

我们对用GSMBE技术生长的In0.63Ga0.37AS／lnP压应变单量子阱样品进行了变温光致发光研究，In0.63Ga0.37As阱宽为1nm到11nm，温度变化范围为10K到300K．发现不同阱宽的压应变量子阱中激子跃迁能量随温度的变化关系与体In0.53Ga0.47As材料相似，温度系数与阱宽无关．对1nm的阱，我们观察到其光致发光谱峰为双峰，经分析表明，双峰结构由量子阱界面起伏一个分子单层所致．说明量子阱界面极为平整，样品具有较高的质量．考虑到组分效应、量子尺寸效应及应变效应，计算了In0.63G0.37As／InP压应变量子阱中的激子跃迁能量，理论计算结果与实验结果符合得很好     

优质量子阱的MBE生长和性能研究

利用国产MBE没备,选择合适的生长参数,获得优质的GaAs/Al_xGa(1-x)As量子阱结构。对共性能和结构参数进行了光荧光测量,荧光峰的形状和温度特性是衡量量子阱质量的重要判据。对n=1的自由激子荧光峰形状进行的讨论和模型分析推得:量子阱界面的平整度达到了单原子层起伏。荧光峰的温度特性表明样品从低温到室温都能保持激子发光特性,量子阱样品的主要性能可与国际水平相媲美。     

GaAsSb/GaAs量子阱激光器结构的发光研究

研究了GaAsSb/GaAs应变量子阱及应变补偿量子阱激光器结构的光致发光和电注入发光.结果表明,分子束外延生长温度的改变使量子阱发光性能发生系统性变化,证明生长温度对量子阱中锑的组分和界面质量具有重要影响. 同时,低温光致发光峰的波长随激发功率密度增大发生明显蓝移,具有Ⅱ类量子阱的特点. 应变补偿量子阱激光器在波长为1.3μm附近激射,阈值电流密度约为1.8kA/cm2.     

In_（0．6）Ga_（0．4）As／InP应变量子阱的光致发光

本文研究了不同阱宽的Ｉｎ０．６Ｇａ０．４Ａｓ／ＩｎＰ应变量子阱的光致发光，通过量子尺寸效应和压缩应变引起的峰值能量位移判断了不同谱峰的跃迁．在一定的温度范围内，相应量子阱的发光强度随着温度的升高而增加，当温度高出此范围，其光强随温度的升高而减小，此温区不仅与阱宽有关。且随激发光强而变化．我们用量子阱的限制效应和激子的转换机理，初步探讨了此温度范围的形成和消失．     

一种1064nm应变双量子阱激光器的设计与制作

为能得窄谱宽、高亮度的1064nm-InGaAs/GaAs应变双量子阱激光器,分析了In组份与临界厚度、应变量的变化关系,并给出了In组份的选择范围。采用Kane模型给出了量子阱中第一分立能级分裂宽度与垒宽的关系,明确了应变双量子阱激光器中垒宽的选择。最后,通过金属有机气相沉积(MOCVD)法生长了1064nm应变双量子阱激光器,实验结果与理论计算的辐射波长值基本吻合。     

应变多量子阱激光器的结构稳定性

通过计算应变多量子阱中的净应力和应变弛豫,讨论了激光器结构中应变多量子阱的稳定性。净应力是失配位错增殖的驱动力,是应变多量子阱稳定的重要判据。因此,用单结点模型计算了应变多量子阱结构中的净应力。计算结果表明,净应力的最大值在应变多量子阱结构中的位置与阱层和垒层的厚度以及阱层的失配有关,非应变垒层和盖层能在一定程度上稀释净应力。在此基础上,利用动力学模型计算了应变多量子阱的应变弛豫。     

Binding energies of shallow impurities in asymmetric strained wurtzite Al_x Ga_(1-x)N/GaN/AIy Ga1-y N quantum wells

The ground state binding energies of hydrogenic impurities in strained wurtzite Al_xGa_1-xN/GaN/Al_yGa_1-yN quantum wells are calculated numerically by a variational method.The dependence of the binding energy on well width,impurity location and Al concentrations of the left and right barriers is discussed,including the effect of the built-in electric field induced by spontaneous and piezoelectric polarizations.The results show that the change in binding energy with well width is more sensitive to the impurity position and barrier heights than the barrier widths,especially in asymmetric well structures where the barrier widths and/or barrier heights differ.The binding energy as a function of the impurity position in symmetric and asymmetric structures behaves like a map of the spatial distribution of the ground state wave function of the electron.It is also found that the influence on the binding energy from the Al concentration of the left barrier is more obvious than that of the right barrier.     

外加电场对GaN/AlxGa1-xN双量子阱中性施主束缚能的影响

在有效质量包络函数理论下,利用变分法计算了未加电场以及加入电场后 双量子阱中施主杂质各种情况下的束缚能,讨论了双量子阱中间势垒高度、施主杂质位置对杂质束缚能的影响。给出了加入电场后施主位置不同时的束缚能和波函数,以及量子阱宽度不同时的束缚能,并且计算了未加电场和加入电场后中间势垒高度变化以及宽度不同时的束缚能。当双量子阱中间垒宽一定时,束缚能随着阱宽的变化会出现一个峰值。在阱宽一定时,随着中间垒宽度的增加,束缚能逐渐减小,并在垒宽增加到一定宽度时双量子阱情况与单量子阱情况相似,束缚能不再明显变化。计算结果对设计和研究 量子阱发光和探测器件有一定的参考价值。     

Excitonic photoluminescence of silicon quantum-well structures

The exciton binding energy and the energies of radiative excitonic transitions in the separate SiO_x-Si-SiO_x quantum wells are calculated in the effective-mass approximation with the quadratic dispersion relation. Along with the real finite offsets of the bands in such quantum well structures, the effect of dielectric enhancement of the exciton binding energy due polarization of the heterointerfaces is taken into account. In addition, the dependence of the zero-phonon radiative excitonic recombination time on the width of the SiO_x-Si-SiO_x quantum well is calculated. This dependence exhibits unsteady (oscillating) behavior, which is caused by the indirect band gap of the silicon material. It is shown that the theoretically calculated energies of the radiative excitonic transitions in the SiO₂-Si-SiO₂ quantum wells match the experimentally determined energies for the quantum wells whose widths are larger than 1.5 nm. Good agreement between the theoretically calculated and experimental spectral dependences of photoluminescence in the SiO₂-Si-SiO₂ quantum wells is attained.     

Theory of electric field-induced optical modulation in single and multiquantum well structures using a Monte Carlo approach

A Monte Carlo approach is used in conjunction with the variational method to calculate quasi-bound levels in arbitrary quantum wells in the presence of transverse electric field. This approach is expected to be superior to the conventional variational approach since the results do not depend upon the choice of any starting wave solution. The technique is applied to Al0.3Ga0.7AS/GaAs quantum wells. The shift in the ground state level energies is calculated, along with the tunneling rates for the electrons and holes. We find that the tunneling rates are very sensitive to the band edge discontinuity distribution and to the barrier width in the case of multiquantum wells. The exciton binding energy is also calculated. Due to high tunneling rates at high electric fields, the photoluminescence is expected to be quenched. Consequences of these results are examined.     

用分数维空间方法研究量子阱中激子效应对三次谐波产生的影响

运用分数维空间方法理论研究了GaAs/AlGaAs无限深和有限深方形量子阱中激子效应对三次谐波产生的影响。利用分数维空间模型获得波函数和束缚能级为空间维度的函数,而空间维度数是阱宽的函数。无限深方阱的维度数随着阱宽的减小从三维极限过渡到二维;而在有限深阱中,当维度数达到一个极值后,维度数随阱宽的减小而增大。采用密度矩阵和迭代法导出三次谐波的表达式。数值结果表明,考虑激子效应的三次谐波系数比只考虑电子状态的系数增大40%左右,并且三次谐波系数大小依赖于激子的受限程度。结果还表明在弛豫率较小情况下可以获得较大的三次谐波的系数。     

Binding energies of shallow impurities in asymmetric strained wurtzite AlxGa1-xN/ GaN/Aly Ga1-yN quantum wells

The ground state binding energies of hydrogenic impurities in strained wurtzite AlxGa1-xN/GaN/AlyGa1-y>N quantum wells are calculated numerically by a variational method. The de-pendence of the binding energy on well width, impurity location and Al concentrations of the left and right barriers is discussed, including the effect of the built-in electric field induced by spontaneous and piezoelectric polarizations. The results show that the change in binding energy with well width is more sensitive to the impurity position and barrier heights than the barrier widths, especially in asymmetric well structures where the barrier widths and/or barrier heights differ. The binding energy as a function of the impurity position in symmetric and asymmetric structures behaves like a map of the spatial distribution of the ground state wave function of the electron. It is also found that the influence on the binding energy from the Al concentration of the left barrier is more obvious than that of the right barrier.     

量子阱中Be受主的光致发光

报道了掺杂在GaAs体材料中和δ掺杂在一系列GaAs/AlAs多量子阱中的Be受主带间跃迁的光致发光.实验所用样品,GaAs体材料中均匀掺杂Be受主的外延单层和一系列量子阱宽度从3到20nm,并在量子阱中央进行了Be受主δ掺杂的GaAs/AlAs多量子阱样品都是通过分子束外延技术制备的.在4,20,40,80及120K不同温度下,分别对上述样品进行了光致发光谱的测量,清楚地观察到了受主束缚激子从1S3/2(Γ6)基态到同种宇称2S3/2(Γ6)激发态的两空穴跃迁,并从实验上得到了不同量子阱宽度下Be受主从1S3/2(Γ6)到2S3/2(Γ6)态的带间跃迁能量.理论上利用变分原理,在单带有效质量模型和包络函数近似下,数值计算了Be受主1S3/2(Γ6)→2S3/2(Γ6)的跃迁能量随量子阱宽度的变化关系,比较发现理论计算和实验结果符合较好.     

Intersubband Raman scattering in InAs/AlSb quantum wells

Raman spectroscopy has been used to study intersubband transitions in InAs/AlSb single quantum wells grown by molecular-beam epitaxy on (100) GaAs substrates using strain-relaxed AlSb or GaSb buffer layers. From the measured energies of the coupled longitudinal optical phonon-intersubband plasmon modes the single particle transition energies between the first and second confined electron subbands were deduced as a function of the width of the pseudomorphically strained InAs well. Subband spacings calculated including the effects of strain and nonparabolicity were found to be in agreement with the experimental transition energies. For a given well width, the two-dimensional electron concentration deduced from the Raman measurements was found to be lower than the concentration measured in the dark by Hall effect, but showed a significant increase with increasing optical excitation intensity.     

Quantum Confinement Effects in Strained SiGe/Si Multiple Quantum Wells

Strained SiGe/Si multiple quantum wells (MQWs) were grown by cold-wall ultrahigh vacuum chemical vapor deposition (UHV/CVD). Photoluminescence measurement was performed to study the exciton energies of strained Si0.84 Ge0.16/Si MQWs with SiGe well widths ranging from 4.2nm to 25.4nm. The confinement energy of 43meV is found in the Si0.84Ge0.16/Si MQWs with well width of 4.2nm. The confinement energy was calculated by solving the problem of a particle confined in a single finite rectangular poteintial well using one band effect mass model. Experimental and theoretical confinement energies are in good agreement     

Photoluminescence of strain-induced coupled InGaAs/GaAs quantum-dot pairs

Coupled quantum dot-pairs were fabricated by growing InP self-assembled islands as stressors on InGaAs/GaAs double quantum wells. State filling in the photoluminescence spectra was used to resolve the quantum states in the coupled dots. The total strain field below the stressor decays exponentially with a penetration depth of about 25 nm, within which a dot-pair can be fabricated. Strong coupling is observed at a barrier width less than 4 nm separating the dot-pair. By increasing the indium composition in the lower well in order to match its dot level with one in the upper dot with identical quantum numbers, resonant coupling between the electron states with identical quantum numbers in the two dots can be achieved. Decoupling of the hole states and exchange of the electron bonding states from dominating the upper dot to the lower one are clearly resolved from the state energies and their spacings.