GaAs／ALGaAs和InGaAs／GaAs窄量子阱中激子线宽与温度的关系

研究了具有不同阱宽的ＧａＡｓ／ＡｌＧａＡｓ和ＩｎＧａＡｓ／ＡｌＧａＡｓ窄量子阱结构中激子线宽与温度的关系，发现在低温范围内，声学声子的线性散射系统随着阱宽的减小而增加，对实验结果作了讨论。     

GaAs／AlGaAs窄量子阱中激子二维特性的退化

用光荧光（ＰＬ）和时间分辨光谱（ＴＲＰＬ）技术研究了ＧａＡＳ／ＡＩＧａＡＳ量子阱结构中荧光上升时间τｆ和激子谱线半宽（ＦＷＨＭ）随阱宽的变化关系，发现在窄阱中，τｆ，随阱宽的变化关系与宽阱时的情况恰恰相反，在窄阱中τｆ随着阱宽的减小而增加，归结为激子二维特性的退化导致声学声子对激子的散射作用减弱造成的．同时观测到窄阱中谱线半宽随着阱宽减小而增加，这也是因为激子特性由维二维向三维转化造成的．     

In_xGa_（1－x）As／Al_yGa（1－y）As多量子阱的高压光致发光研究

用金刚石对顶砧压力装置在液氮温度下和０～４ＧＰａ的压力范围内测量了不同阱宽（１．７～１１．０ｎｍ）的ＩｎｘＧａ（１－ｘ）Ａｓ／Ａｌ（１－ｙ）Ｇａ（１－ｙ）Ａｓ（ｘ，ｙ＝０．１５，０；０．１５，０．３３；０，０．３３）多量子阱的静压光致发光谱，发现在Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ多量子阱中导带第一子带到重空穴第一子带间激子跃迁产生的光致发光峰能量的压力系数随阱宽的增加而减小，在Ｉｎ０．１５Ｇａ０．８５Ａｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ和ＧａＡｓ／Ａｌ０．３３Ｇａ０．６７Ａｓ多量子阱中相应发光峰的压力系数随附宽的增加而增加．根据Ｋｒｏｎｉｙ－Ｐｅｎｎｅｙ模型计算了发光峰能量的压力系数随阱宽的变化关系，结果表明导带不连续性随压力的增加（减小）及电子有效质量随压力的增加是压力系数随阱宽增加而减小（增加）的主要原因．     

InxGa1—xAs／AlyGa1—yAs多量子阱的高压光致发光研究

用金刚石对顶砧压力装置在浓氮温度下和０～４ＧＰａ的压力范围内测量了不同阱宽（１．７～１１．０ｎｍ）的ＩｎｘＧａ１－ｘＡｓ／ＡｌｙＧａ１－ｙＡｓ（ｘ，ｙ＝０．１５，０；０．１５，０．３３；０，０．３３）多量子阱的静压光致发光谱，发现在Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ多量子阱中导带第一子带到重空穴第一子带间激子跃迁产生的光致发光峰能量的压力系数随阱宽的增加而减小，在Ｉｎ０．１５Ｇａ０．８５Ａｓ／     

压变应In0.63Ga0.37As／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／ＩｎＰ压应变单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，发现不同阱宽的压变变量子 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，双峰结构由量了阱界面起伏一个分子单     

InGaAs／GaAs应变量子阱的低温光伏谱

用光伏谱方法研究了ＩｎＧａＡｓ／ＧａＡｓ应变量子阱结构中各子能级间的光跃迁，并与理论计算的结果进行了比较．分析了光伏谱峰能量随阱宽与温度的变化，并讨论了光伏谱峰强度的温度关系．     

InGaAs/GaAs应变量子阱光伏谱激子峰展宽的研究

实验得到不同温度下应变ＩｎＧａＡｓ／ＧａＡｓ量子阱的光伏谱，通过理论计算与实验结果的比较，对各谱峰进行了指认．本文着重考察各样品中１１Ｈ跃迁的激子谱峰的半宽随温度及阱宽的变化，讨论谱峰展宽机制中的声子关联、混晶组分起伏及界面不平整对线宽的影响．     

InAs／GaAs亚单层结构的静压光谱研究

在１５Ｋ下测量了ＩｎＡｓ／ＧａＡｓ亚单层结构的静压光致发光，静压范围为０～８ＧＰａ．常压下ＩｎＡｓ层中重空穴激子的发光峰随ＩｎＡｓ层厚的减小向高能移动，同时峰宽变窄，强度减小．其压力行为与ＧａＡｓ基体的基本一致，表明量子阱（线、点）模型仍适用于ＩｎＡｓ／ＧａＡｓ亚单层结构．得到平均厚度为１／３单分子层的样品中由于附加的横向限制效应引起的电子和空穴束缚能的增加分别为２３和４２ｍｅＶ     

InGaAs／GaAs应变量子阱中的激子发光动力学

本文详细测量并分析了ＩｎＧａＡｓ／ＧａＡｓ应变量子阱中的激子发光衰退特性，研究了激子发光寿命与Ｉｎ组分和阱宽的关系．发现Ｉｎ组分增大时，激子寿命变短，而发光寿命与阶宽的关系不大．文章分析了影响发光寿命的诸多因素，指出在ＩｎＧａＡｓ／ＧａＡｓ量子阱中，由合金无序造成的散射对激子发光寿命有重要的影响．     

GaAs／AlGaAs多量子阱结构的热电子效应

采用低温荧光激发光谱研究了ＧａＡｓ／ＡｌＧａＡｓ多量子阱结构中热电子的驰豫过程，在ＰＬＥ谱中首次观察到ＧａＡｓ／ＡｌＧａＡｓ多量子阱中ＬＯ声子的发射，用四能带Ｋａｎｅ模型计算了由轻、重空穴杂化效应引起的价带结构的畸变及其对声子发射谱的影响，实验和理论计算结果均表明、光激发热电子可以通过发射ＬＯ声子直接弛豫到激子态上，实现热电子的冷却。     

GaInNAs/GaAs量子阱的光致发光谱和光调制反射谱

研究了GaInNAs/GaAs多量子阱在不同温度和激发功率下的光致发光(PL)谱以及光调制反射(PR)谱.发现PL谱主发光峰的能量位置随温度的变化不满足Varshni关系,而是呈现出反常的S型温度依赖关系.进一步测量,特别是在较低的激发光功率密度下,发现有两个不同来源的发光峰,它们分别对应于氮引起的杂质束缚态和带间的激子复合发光.随温度变化,这两个发光峰相对强度发生变化,造成主峰(最强的峰)的位置发生切换,从而导致表观上的S型温度依赖关系.采用一个基于载流子热激发和出空过程的模型来解释氮杂质团簇引起的束缚态发光峰的温度依赖关系.     

非对称耦合双阱P—I—N结构的光伏谱研究

首次报道了GaAs/Al_(0.35)Ga_(0.65)As/GaAs(50(?)/40(?)/100(?))非对称耦合双阱P-I-N结构的室温光伏谱,清楚地观察到双阱的轻、重空穴激子峰,这些激子峰的能量位置与光荧光和光电流谱得到的数据吻合得很好,而且光伏谱谱形非常类似于光电流谱,呈现清晰的台阶状结构。此外,还观察到轻、重空穴激子跃迁对激发光偏振态的依赖,并讨论了产生光伏谱的机制。     

GaInAs/AlGaAs应变量子阱结构的荧光特性

本文报道了4—300K温度范围内量子阱宽度分别为20、40、90和130A的GaInAs/AlGaAs应变量子阱结构的光荧光特性。我们考虑量子尺寸对载流子子能带的影响和弹性应变引起带隙的移动,计算了量子阱中本征激子发光的能量位置,计算值与实验结果基本吻合。还研究了荧光峰强度随阱宽的变化以及不同温度下荧光峰的半高宽度。     

Mapping of two-photon luminescence amplification in zinc-oxide microstructures

The mapping of two-photon excited luminescence in aggregations of free-standing zinc oxide microrods has been carried out at room temperature. Two-photon luminescence spectra in the excitonic region for individual microrods have been recorded. The luminescence intensity exhibits a power-law dependence on the optical pump power with the exponent n > 2. This fact, along with the existence of a threshold power above which the dependence in the exciton region deviates from a quadratic one, indicates the onset of light amplification in individual ZnO microrods and the conditions preceding laser oscillation.     

Ultra-thin GaxIn1−xAs/InP (0≤x≤0.47) layer growth by chemical beam epitaxy

Ga_xIn_1?xAs/InP (0≤x≤0.47) lattice-matched and compressively strained quantum wells were grown by all gas source chemical beam epitaxy (CBE). Their optical properties were investigated by photoluminescence (PL) and optical absorption measurements. The thinnest Ga_xIn_1?xAs layer was 6Å-thick (2 monolayers) for Ga_0.47In_0.53As and 3Å-thick (1 monolayer) for InAs. In PL measurements, we found that for strained materials (x<0.47) luminescence intensity dropped with decreasing barrier thickness. Optical absorption properties were measured at room temperature, and excitonic absorption peaks were clearly observed. The wavelengths of excitonic peaks were in good agreement with a theoretical estimation obtained by using an effective mass approximation including heavy and light hole energy splitting at the γ point.     

Nonlinear absorption properties of AlGaAs/GaAs multiple quantumwells grown by metalorganic chemical vapor deposition

The nonlinear absorption properties of the excitonic resonances associated with multiple quantum wells (MQWs) in AlGaAs/GaAs grown by metalorganic chemical vapor deposition are reported. The dependence of the saturation properties on growth parameters, especially growth temperature, and the well width are described. The minimum measured saturation intensity for these materials is 250 W/cm², the lowest reported value to date. The low saturation intensities are the result of excellent minority carrier properties. A systematic study of minority carrier lifetimes in quantum wells are reported. Lifetimes range from 50-350 ns depending on growth temperature and well width     

Temperature dependence of excitonic transition in ZnSe/ZnCdSe quantum wells

In recent years ,the interest in the quantum hetero-structures composed of theⅡ-Ⅵwide gap materials haveincreased dueto potential device applications ,suchasthehigh-brightness blue/green light emitting diodes(LEDs) andlaser diodes (LDs)[1].Sincethe applicationof semiconductor materials to optoelectronic devices re-quires a precise design of the optical properties at theoperation temperature, it is i mportant to have theknowledge of the temperature effects on the opticalproperties of the mat…     

Luminescence from ZnO quantum dots deposited with synthetic opal

Photoluminescence from ZnO layers of varied thickness deposited onto the surface of synthetic opal has been studied. Narrow peaks of luminescence in the excitonic spectral range, related to quantum confinement of the electron wave functions, have been observed. The formation of ZnO quantum dots (QD) within the opal voids in the second subsurface layer has been confirmed by atomic force microscopy and by studying the angular dependence of the luminescence spectra.     

Exciton recombination in δ-doped type-II GaAs/AlAs superlattices

Radiative recombination of excitons in δ-doped type-II GaAs/AlAs superlattices (SLs) is studied experimentally. With an increase in the impurity density in δ-layers from 2×10¹⁰ to 7.5×10¹¹ cm^?2, the integrated intensity of SL photoluminescence (PL) decreases by a factor of 4–6; the intensity of excitonic PL drops considerably (up to 70–80 times), which is accompanied by an increase in the exciton radiative decay rate. Uniform doping of the SL does not result in the exciton PL quenching. Analysis of the temperature dependence and the kinetics of the PL indicate that impurity quenching of the excitonic PL in δ-doped structures is not related to a reduction in the exciton localization energy and cannot be explained by an increase in the density of nonradiative recombination centers. We conclude that the PL quenching is mainly caused by the appearance of built-in electric fields originating from ionized impurities, which hinders the formation of the excitons.     

Excitons and polaritons in AlGaAs semiconductor alloys

For Al_xGa_1?x As semiconductor alloys with x = 0.15 and 0.21 at temperatures T = 1.7?380 K, the band-edge absorption spectra are measured and the temperature dependence of the integrated absorption coefficient is obtained. The results are analyzed in the context of two mechanisms of the exciton-polariton energy transfer that can lead to the variation of the integrated absorption in systems with random excitonic potential at low temperatures. In one case, the temperature anomaly in the absorption results from the competition between the excitonic and electromagnetic mechanisms of the energy transfer in a quasi-homogeneous medium (a virtual crystal) with spatial dispersion. In the other case, the effect is related to the reemission of light by resonance localized excitons along finite chains of quantum wells in the absence of excitonic transfer. The observation of a characteristic temperature dependence of the integrated absorption supports the existence of exciton polaritons in the samples under study. It is found that integrated absorption in Al_0.15Ga_0.85As alloy saturates above the critical temperature T _c = 155 K. It is demonstrated that, in the temperature range from 1.7 to 60 K, the inhomogeneous broadening due to the fluctuating potential is responsible for the dominant contribution to the width of the excition line in the alloys investigated and considerably exceeds the homogeneous broadening caused by the interaction of excitons with phonons and charged impurities.