分子束外延ZnSe/ZnS_xSe_(1-x)超晶格光学特性

用分子束外延方法在 Ga As(10 0 )衬底上生长了高质量的 Zn Se/ Zn Sx Se1 - x(x=0 .12 )超晶格结构 ,通过 X射线衍射谱和光致发光谱 ,对其结构特性和光学特性进行了研究 .结果表明 :在 4 .4 K温度下 ,超晶格样品显示较强的蓝光发射 ,主发光峰对应于阱层 Zn Se的基态电子到重空穴基态的自由激子跃迁 ,而且其峰位相对于 Zn Se薄膜的自由激子峰有明显蓝移 .从理论上分析计算了由应变和量子限制效应引起的自由激子峰位移动 ,理论和实验结果相吻合     

GaAs/GaAlAs多量子阱激子吸收谱

在10K至292K温度范围内测量了GaAs/GaAlAs多量子阱结构的激子吸收谱.观察到轻、重空穴对应的激子吸收峰(LH和HH)及台阶状态密度.研究了轻、重空穴激子吸收峰的能量间隔及激子吸收峰的温度特性.发现多量子阱样品的LO声子展宽系数为6.1meV,比体GaAs的展宽系数略小.样品用国产MBE设备生长,采用化学选择腐蚀技术除去GaAs衬底.     

用LPE生长1.35μm InGaAsP/InP量子阱结构的研究

在国内首次利用LPE生长技术在n-InP(100)衬底上成功地生长1.35μm InGaAsP分别限制单量子阱结构。通过对样品的横截面进行的TEM观测,量子阱的阱宽和过渡层的厚度分别为160A和30A。在10K和77K光致发光谱测量中,我们观察到n=1的子能级上电子到重、轻空穴带很强的自由激子跃迁峰,两峰间隔为8.3meV,在低温条件下光致发光谱的半高宽度为20meV。     

ZnSe-ZnS超晶格材料的光学特性

本文首次报道了ZnSe-ZnS应变层超晶格的分子束外延生长.对材料进行了光荧光谱、远红外反射谱及喇曼光谱测量.得到了激子发射峰的移动随ZnSe阱宽及温度的变化以及发射峰半宽随温度的变化.首次在室温下测量到该材料的三级纵声学声子折叠模.通过对远红外反射谱的计算机拟合,确定了ZnSe、ZnS材料的几个基本声子参数.我们还首次在室温下观测到ZnSe-ZnS多量子阱标准具有明显的脉冲压缩效应.     

准二维强耦合激子能量的温度依赖性

采用线性组合算符法和LLP变分法研究了晶格热振动和极化子效应对量子阱中激子与界面光学(IO)声子强耦合又与体纵光学(LO)声子弱、中耦合体系的基态和激发态的影响,推导出作为量子阱宽和温度函数的激子基态能量的移动和第一内部激发态能量的移动的表达式,以AgCl/AgBr/AgCl量子阱为例进行了数值计算.结果表明,由激子IO声子强耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而增大,而由激子-LO声子弱、中耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而减小.     

准二维强耦合激子能量的温度依赖性

采用线性组合算符法和LLP变分法研究了晶格热振动和极化子效应对量子阱中激子与界面光学(IO)声子强耦合又与体纵光学(LO)声子弱、中耦合体系的基态和激发态的影响,推导出作为量子阱宽和温度函数的激子基态能量的移动和第一内部激发态能量的移动的表达式,以AgCl/AgBr/AgCl量子阱为例进行了数值计算.结果表明,由激子IO声子强耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而增大,而由激子-LO声子弱、中耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而减小.     

Mg掺杂AlInP 650 nm LD外延片的Zn扩散研究

利用石英闭管法,对Mg掺杂AlInP 650 nm LD外延片进行Zn扩散,分析了扩散温度和时间2个参数对Zn扩散的影响.采用光致发光(PL)谱和电化学蒸涂(ECV)方法研究了Zn扩散产生的影响.PL谱结果表明,Zn扩散引起了AlGaInP/GaInP多量子阱(MQW)有源层的组分无序,使PL谱的峰值蓝移,最大蓝移为54 nm,约175 meV.ECV测量结果显示,Zn已经扩散到MQW有源区,MQW区域的p型载流子浓度为4.4×1017 cm-3.     

ZnSe/ZnCdSe多量子阱激子光学非线性

本文采用泵浦－探测技术研究了ＺｎＳｅ／ＺｎＣｄＳｅ多量子阱室温激子饱和吸收，并根据Ｋ－Ｋ关系计算得到５２１．６ｎｍ至５４４ｎｍ的光学非线性折射率的变化．观测到由折射率变化引起的ＺｎＳｅ／ＣｄＺｎＳｅ多量子阱光双稳器件的室温激子光双稳．根据ＺｎＳｅ／ＺｎＣｄＳｅ多量子阱的激子吸收谱及激子的非线性理论，归结其主要非线性机制为激子态的相空间填充和激子带展宽．     

非对称耦合量子阱ZnCdSe/ZnSe的喇曼散射谱与非线性光学特性

采用荧光光谱和喇曼散射谱对非对称Ⅱ一Ⅵ族耦合多量子阱Zn1-xCdxSe／ZaSe的结构进行了表征，并对它的非线性光学特性进行了研究。实验中观察到了比较明显的量子阱荧光峰：在喇曼散射谱中观察到了分别对应于与ZnCdSe窄阱和宽阱的一级限制光学模LO1(Lowe Well)和LOI(Wide Well)，及对应于ZnSe／GaAs界面的声子和等离子体的耦合模。实验发现二次谐波信号的强度随着阱间耦合的增强而增强，说明非对称量子阱(AQW)的耦合效应存在一阈值．与理论结果相一致。     

应变CdTe/Cd_(0.633)Mn_(0.367)Te单量子阱结构的光致发光谱

本文报道应变CdTe／Cd0.633Mn0.367Te单量子阱中光致发光光谱．结合理论计算得到导带不连续因子Qc为0．92±0．01．讨论了量子阱中的能带填充效应．实验发现量子阱中的发光结构在整个测量温度下（20～200K）都为激子跃迁，其线型展宽主要由纵光学声子决定．高温下此量子阱中辐射复合效率降低的主要机制是载流子热激发出势阱，并伴随着在势垒中的非辐射复合．     

Synthesis and photoluminescence properties of the 4H-SiC/SiO2 nanowires

4H-SiC/SiO2 nanowires are synthesized and the temperature-dependent photoluminescence （PL） properties of the nanowires are studied. Their structure and chemical composition are studied by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, and Raman spectra. At room temperature, an ul- traviolet PL peak and a green PL band are observed. From the PL spectrum measured in the temperature range from 80 K to 300 K, the free excition emission, donor bound excition emission and their multiple-phonon replicas have been observed in ultraviolet region, and their origins have been identified. Moreover, it has been found that the temperature dependence of the free exciton peak position can be described by standard expression, and the thermal activation en- ergy values extracted from the temperature dependence of the free exciton and bound exciton peak integral intensity are about 40 meV and 181 meV, respectively.     

Optical reflection and contactless electroreflection from GaAlAs layers with periodically arranged GaAs quantum wells

Optical reflection and electroreflection for the AlGaAs layers containing the periodically arranged GaAs quantum wells of different thickness are studied at photon energies ranging from 1 to 2 eV. It is established that the spectral dependence of the reflectance involves three different contributions made by (i) the reflection from the medium-air interface; (ii) the interference reflection due to the periodically modulated refractive index, since the materials of the wells and barriers have different refractive indices; and (iii) the reflection produced by the interaction of electromagnetic waves with the excition states in the quantum wells. Analysis of the reflection spectra shows that these contributions are characterized by different behavior with variations in temperature, angle of incidence of light, and polarization; however, quantitative separation of the spectra into individual contributions presents a rather difficult problem. To separate the contribution originating from the interaction of light with the exciton states from the optical spectra, a special approach based on contactless measurements of the optical electroreflectance over a certain spectral region is developed. It is shown that this method provides a means for determining the parameters of the exciton states in the quantum wells.     

CdTe／Cd_（1－x）Mn_xTe：In应变层量子阱的光荧光光谱

报道了ＭＢＥ生长的ＣｄＴｅ／Ｃｄ１－ｘＭｎｘＴｅ：Ｉｎ调制掺杂应变层多量子附材料的光荧光光谱，低温下观察到一个由多电子－单个空穴散射引起的很强的费密边奇异的发光现象，对应于费密边能量位置发光峰有一个很强的增加，使整个发光锋具有明显的非对称性．分析讨论了引起费密边奇异现象的物理机制，测量了７７Ｋ下ＣｄＴｅ／Ｃｄ１－ｘＭｎｘＴｅ：Ｉｎ样品的调制光谱，与荧光光谱进行了比较，结果进一步支持了本文的结论．还测量了费密迪奇异随温度的变化，结果表明此现象在Ⅱ—Ⅵ族半导体多量子附材料中比Ⅲ─Ｖ族材料强得多．     

MOCVD生长的CdZnTe／ZnTe多量子附的激子光学特性

用常压ＭＯＣＶＤ方法在ＧａＡｓ（１００）衬底上生长了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱。在室温下，观测到了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的三个谱带发光。根据ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的吸收光谱和不同激发光强下的发光光谱，分别归结ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱中观测到的三个发光谱带于覆盖层发光、ｎ＝１的重空穴激子发光及杂质发光。     

利用P-MBE在Si(111)衬底上生长氧化锌薄膜及其光学性质的研究

在Si(111)衬底上利用等离子体辅助分子束外延(P-MBE)生长氧化锌(ZnO)薄膜,研究了在不同衬底生长温度下(350～750℃)制备的ZnO薄膜的结构和光学性质．随着衬底温度的升高,样品的X射线及光致发光的半高宽度都是先变小后变大,衬底温度为550℃样品的结构及光学性质都比较好,这表明550℃为在Si(111)衬底上生长ZnO薄膜的最佳衬底温度;同时,我们还通过550℃样品的变温光致发光谱(81～300K)研究了ZnO薄膜室温紫外发光峰的来源,证明其来源于自由激子发射．     

Optical spectroscopy of a resonant Bragg structure with InGaN/GaN quantum wells

The optical reflectance and transmittance spectra of a periodic InGaN/GaN semiconductor heterostructure with 60 quantum wells are studied at room temperature. The period of the structure was chosen such that, at some angles of incidence of light, the energy of a photon resonantly reflected from the Bragg structure coincides with the excitation energy for quantum-well excitons in quantum wells. The parameters of these excitons are determined by fitting the spectra measured at two different angles of incidence, 30° and 60°. We take into account the resonant exciton transitions in quantum wells as well as the transitions into the continuous spectrum. The radiative decay parameter is determined to be (0.20 ± 0.02) meV.     

Photoluminescence characteristics of GaN/lnGaN/GaN quantum wells

Photoluminescence (PL) characteristics of GaN/lnGaN/GaN single quantum wells (QWs) and an InGaN/GaN single heterojunction were studied using continuous wave (CW) and pulsed photoluminescence in both edge and surface emitting configurations. Samples were grown on c-plane sapphire substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD). Room temperature and 77K PL measurements were performed using a CW Ar-ion laser (305 nm) and a frequency tripled (280 nm), pulsed, mode-locked Ti: sapphire laser. CW PL emission spectra from the quantum wells (24, 30, 80Å) were all blue shifted with respect to the reference sample. The difference (i. e., the blue shift) between the measured value of peak emission energy from the QW and the band-edge emission from the reference sample was attributed to quantum size effects, and to strain arising due to a significant lattice mismatch between InGaN and GaN. In addition, stimulated emission was observed from an InGaN/GaN single heterojunction in the edge and surface emitting configu-ration at 77K. The narrowing of emission spectra, the nonlinear dependence of output emission intensity on input power density, and the observation of a strongly polarized output are presented.     

碲锌镉体单晶的Raman—PL光谱的分析

文章对碲锌镉（CZT）（111）取向的拉曼光谱和光荧光谱作了分析。在拉曼光谱中,用正斯托克斯测量检测无峰,而反斯托克斯（Anti-Stokes）测出了它的拉曼光谱。其中在（－125cm^-1）处是横声子振动（TO）,（－142cm^-1）处是纵声子振动（LO）。由于晶体的各向异性,在一个平面上,同一晶粒旋转不同方向TO／LO比值与（111）平面等能面截面图相符。另它的PL光谱在807nm(1.535eV),FWHM为30nm(0.057eV),旋转方向对PL光谱无影响。故在生长HgCdTe单晶薄膜时,要注意衬底CZT的晶体摆放位置 。     

GaAs/InGaAs应变异质结构临界厚度的Raman散射和PL谱分析

采用室温Raman散射和低温光致发光(PL)谱,对以TMG,固体As和固体In作为分子束源的MOMBE法生长的GaAs/In_xGa_(1-x)As(x=0.3)单层异质结构和多量子阱结构中InGaAs应变层的临界厚度进行了实验研究。由应变引起的Raman散射峰位移,以及PL谱峰位置与应变和无应变状态下一维有限深势阱跃迁能量计算结果的比较可见,在In组分含量x=0.3的情况下,临界厚度H_c≤5nm,小于能量平衡理论的结果,而与力学平衡模型的理论值相近。     

磁控溅射Ge/Si多层膜的发光特性研究

采用磁控溅射技术,在Si(100)衬底上制备了一系列不同周期、不同Ge层厚度的Ge/Si多层膜样品.用室温光致发光(PL)、Raman散射和AFM图谱对样品进行表征.结果表明:Ge/Si多层膜中的PL发光峰主要来自于Ge晶粒,并且Ge晶粒生长的均匀性对PL发光影响较大,生长均匀的Ge晶粒中量子限域效应明显,随着晶粒的减小,PL发光主峰发生蓝移;在Ge晶粒均匀性较差时,PL发光峰强度较弱,量子限域效应不明显.