CdTnTe（CZT）单晶体的Raman—PL光谱的再分析

本文对碲锌镉（CZT）（111）取向的Raman光谱和PL光谱作了分析。在Raman光谱中,用Stokes测量检测无峰,而反斯托克斯(anti-Stokes)测出了它的Raman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。     

Low-threshold semiconductor Raman laser

A semiconductor Raman laser using the longitudinal optical (LO) phonon mode of GaP has a very low threshold compared to the transverse optical (TO) phonon mode of GaP and even compared to simulated Raman scatterings in various kinds of liquids and insulating solid materials. The lowest threshold value of the pulsed input optical power is 8 kW (5 times 10^{6}W/cm²) at room temperature. Far infrared radiation (24.8 μm) has been generated by placing both GaP with the LO phonon mode and GaAs with the TO phonon mode in a Fabry-Perot resonator. The maximum far infrared power has been 3 W.     

GaAs/Al_xGa_(1-x)As超晶格中的纵光学声子模(英文)

The long wavelength optical phonon spectra of AlxGa1-xAs mixed crystals appear as "two-mode" behaviour, i.e. there are GaAs-like and AlAs-like optical branches simultaneously. Besides* the LO phonon dispersion curves of bulk GaAs and GaAs-like in AlxGa1-xAs mixed crystal are partly overlapped. Therefore, we expect, in GaAs/AlxGa1-xAs superlattices, that LO phonons are partly in confined modes while partly in folded one, and that AlAs-like modes are confined in AlxGa1-xAs layers.The samples of GaAs/AlxGa1-xAs superlattices were grown by MBE on (001) oriented semi-insulating GaAs substrates. Raman spectra were measured in the back-scattering geometry at room temperature. Only odd modes with B2 symmetry were observed for LO modes confined in the GaAs layer. This result is in agreement with the previous reports. In addition, AlAs-like LO modes confined in AlxGa1-xAs layers were observed for the first time.     

Optical characterization of [111]B InGaAs layers

Strain assessment of [111]B InGaAs/GaAs layers, of several compositions and variable thicknesses, has been performed by photoluminescence and Raman spectroscopies. Both the gap energy and GaAs-like LO frequency undergo a blue shift proportional to the residual strain, which can be thus determined. The critical layer thickness for [111]B orientation is found to be three times larger than for [001] layers grown simultaneously. In addition, two kinds of inhomogeneities in the relaxation are found: strain domains, demonstrated by the spectral and spatial resolution of photoluminescence excitation, micro-photoluminescence and micro-Raman experiments; and a change in the strain release with layer depth, obtained by Raman at different excitation energies.     

分子束外延生长CdTe／ZnTe超晶格室温喇曼散射

首次报道了室温和非共振条件下,分子束外延(MBE)生长的CdTe/ZnTe超晶格的喇曼散射测量和分析。观察到最低级次的CdTe和ZnTe纵光学声子限制模,并用应力和限制效应精确计算了频移,得到的ZnTe纵光学声子频移理论值与实验结果符合得较好。特别指出,当CdTe和ZnTe层厚小于2nm时,声子频移的限制效应不可忽略,对所测样品的喇曼全谱作了分析。     

热壁外延生长GaAs／Si薄膜质量研究

本文研究了用热壁外延（HWE）技术在Si衬底上不同工艺下生长的GaAs薄膜的拉曼（Raman)和荧光（PL）光谱。研究表明：在室温下,GaAs晶膜的Raman光谱的265cm^-1横声子（TO）峰和289cm^-1纵声子（LO）峰的峰值之比随晶膜质量的变化而逐渐变大、半高宽（FWHM）变窄且峰值频移动变小,而LC光谱出现在871nm光谱的FWHM较窄,表明所测得的薄膜为单晶晶膜,对同一晶膜也可判断出均匀程度。因此可以通过拉曼光谱和PLC光谱相结合评定外延膜晶体质量。     

GaAs/AlAs超晶格中的TO声子限制模

本文报道在室温和非共振散射条件下,GaAs/AlAs 超晶格结构中TO声子限制模的拉曼散射测量结果.超晶格样品用MBE方法生长在<001>晶向的GaAs衬底上.在背散射条件下,具有E对称性的TO 声子是拉曼禁戒的.但是利用近布儒斯特角入射和大孔径的散射光收集透镜,我们观测到分别限制在GaAs和AlAs层中的TO声子模.其中,限制在AlAs层中的TO模是首次报道.从测量的TO声子限制模频率得到的声子色散曲线与GaAs和AlAs体材料的TO声子色散曲线进行比较,二者符合良好.进一步证明,超晶格结构的拉曼散射测量是测定晶体声子色散曲线的有效的实验方法.     

Elastic strains and delocalized optical phonons in AlN/GaN superlattices

In the context of the dielectric continuum model, a correlation is established between the frequencies of delocalized A(TO) and E(LO) phonons in the Raman spectra of short-period AlN/GaN superlattices and the ratio between the layer thicknesses in the structure. It is shown that elastic strains produced in the materials of the layer during superlattice growth only slightly influence the correlation dependence of the frequencies of A(TO) and E(LO) modes with high intensities in the Raman spectra on the structural parameter defining the ratios between the layer thicknesses. The results of calculations of the phonon frequencies are in good agreement with available experimental data and can be used for spectroscopic diagnostics of AlN/GaN superlattices.     

Spatially resolved optical spectroscopy of GaAs islands on InAs (111)

Three-dimensional micrometer-sized GaAs islands, with pyramidal shapes, have been grown by metal organic vapour phase epitaxy on (111)B InAs. The local strain profile in a single isolated pyramid is deduced from spatially resolved Raman and photoluminescence measurements. High residual tensile strains are found in the GaAs layer surrounding the pyramid. The strain in the pyramid is progressively relaxed from the bottom to the top (nearly strain-free). Furthermore, the Raman selection rules are correlated to the [111] substrate orientation and the high index pyramid facets.     

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 。     

Oblique Raman and polariton scattering in lithium iodate

We have predicted and measured tuning of the LO and TO oblique Raman and the oblique polarition frequencies in the 769-848 cm^-1spectral region in lithium iodate. Oblique scattering in LiIO3is produced by coupling ofAandEsymmetry crystal modes. The resulting LO and TO frequencies lie between the frequencies of the contributing modes. The intensity of the scattered light observed indicates that construction of CW or quasi-CW stimulated oblique Raman and polariton oscillators are possible.     

静压下ZnS0.02Te0.98混晶的共振喇曼散射研究

在１５Ｋ和１～３ＧＰａ静压范围内研究了ＺｎＳ０．０２Ｔｅ０．９８混晶的共振喇曼散射，样品用ＭＢＥ方法生长在（００１）晶向的半绝缘ＧａＡｓ衬底上，利用静压调制带隙实现也４８８．０ｎｍ线的共振喇曼散射，观察到类ＺｎＴｅ和类ＺｎＳ两类ＬＯ声子模以及它们的倍频模和组合模－测得类ＺｎＴｅ的ＬＯ声子模的压力系数为４．５ｃｍ＾－１／ＧＰａ。     

MBE growth and Raman analysis of [hhk]GaAs/(Si or CaF2) highly strained hetero-structures

Highly strained GaAs layers have been grown by molecular beam epitaxy on (100)-, (111)- or (112)-oriented Si or CaF₂ substrates. The origin, sign, bisotropic nature, value, homogeneity and relaxation of the built-in strain have been studied by Raman spectroscopy. Specific measurements have been performed by using selection rules and line shape analysis over a wide temperature range.     

GaN薄膜的微区Raman散射光谱

报道了低压 MOCVD生长的同一 Ga N薄膜不同位置的微区 Raman散射光谱 .观测到了微区结构不完整对 Raman谱的影响 .通过 X射线衍射分析 ,证实了该样品晶体质量是不均匀的 ,而且微结构缺陷的存在是导致回摆曲线展宽的主要原因 .结合 Hall测量结果 ,对 Ga N薄膜的 Al( L O)模式的移动进行了电声子相互作用分析 ,认为 A1 ( LO)模式的移动可能与电声子相互作用无关 ,而是受内部应力分布不均匀的影响所致 .     

碲镉汞体材料的显微Raman光谱

利用Raman显微镜测量了ACRT-Bridgman方法和Te溶剂方法生长的碲镉汞体材料的显微Raman光谱，在碲镉汞体材料的显微Raman光谱中识别出了碲镉汞的基本光学振动模，由此证明了碲镉汞按晶格振动的分类方法属于二模混晶；识别出了一个来源于类HgTe的TO1模 LO1模的二级Raman散射峰；观察到了碲镉汞体材料中两个新的Raman散射峰，分别位于662cm^-1和749cm^-1；观察到了碲镉汞基本光学振动模的TO1模与LO1模的Raman散射强度比的变化，指出该现象是由于Raman散射几何配置不同引起的。     

纳米碳管模板法制取的GaP纳米棒拉曼光谱研究

报道了用纳米碳管模板法制备的GaP纳米棒的拉曼光谱特征，观测到声子限制效应引起的GaP纳米棒TO和LO模的红移，红移量一般在2－10cm^-1之间，与所测到的纳米棒的尺寸有关，在偏振特性研究中，发现GaP纳米棒的偏振特性不能用单根纳米棒的选择定则来解释，而与测量光斑内多根纳米棒的无序取向有关，无序程度越高，偏振特性的方向性越弱，当激发光功率增加时，GaP纳米棒的TO和LO模的频率显著减少，表明纳米棒中的激光加热效应比体材料中强很多，而且GaP纳米棒的拉曼散射强度随激发光功率的增加先饱和，然后减小，表明在强激发功率下GaP纳米棒中的缺陷会迅速增加。     

用MOCVD方法制备的GaN_(1-x)P_x三元合金的喇曼与红外光谱

采用光辐射加热低压金属有机化学气相淀积(L P- MOCVD)方法在蓝宝石衬底上生长了高P组分的Ga N1 - x-Px 三元合金薄膜,通过喇曼光谱和红外反射谱技术研究了Ga N1 - x Px 合金中P掺杂所引入的振动模.与非掺P的Ga N相比,在Ga N1 - x Px 合金的喇曼谱和红外反射谱中分别观测到了多个由P所引入的振动模,文中将它们分别归因于Ga- P键振动引起的准局域模、间隙模以及P掺入造成的局部晶格无序激活的振动模     

Strain Distribution Across HVPE GaN Layer Grown on Large Square-Patterned Template Studied by Micro-Raman Scattering

A self-separated GaN layer was prepared by hydride vapor phase epitaxy on a large-period square network template. The morphology of the surface formed was consistent with the substrate patterning that comprised terrace and concave. The mixed polarity of the surface was studied by wet etching and micro-Raman scattering. Micro-Raman scattering was performed to investigate the strain distribution of the surface on the front and backside, as well as the cross-section. Differences were observed in the Raman phonon peaks such as the A₁(LO), E₁(TO), E₂(high) phonon, and LO phonon–plasmon mode (LPP^?)/A₁(TO) peaks between the terrace and concave. The strain distribution varied regularly, which was interpreted based on the facet growth mode.     

生长于4H-SiC和蓝宝石衬底上的GaN的Raman光谱和高分辨率XRD研究分析

The crystal quality, stress and strain of GaN grown on 4H-SiC and sapphire are characterized by high resolution X-ray diffraction（HRXRD） and Raman spectroscopy.The large stress in GaN leads to the generation of a large number of dislocations.The Raman stress is determined by the results of HRXRD.The position and line shape of the A1 longitudinal optical（LO） phonon mode is used to determine the free carrier concentration and electron mobility in GaN.The differences between free carrier concentration and electron mobility in GaN grown on sapphire and 4H-SiC are analyzed.     

静压下（CdSe）_m／（ZnSe）_n－ZnSe超短周期超晶格量子阱的共振喇曼散射研究

在静压和液氮温度下观察到（ＣｄＳｅ）ｍ／（ＺｎＳｅ）ｎ短周期超晶格中重空穴激子的复合发光和多达４阶的类ＺｎＳｅＬＯ多声子喇曼散射，并观察到厚ＺｎＳｅ势垒层的带边发光和限制在厚势垒层中的类ＺｎＳｅＬＯ声子散射．结果表明，加压后（ＣｄＳｅ）ｍ／（ＺｎＳｅ）ｎ短周期超晶格中的类ＺｎＳｅ的１ＬＯ和２ＬＯ声子模频率分别以３．７６和７．１１ｃｍ－１／ＧＰａ的速率向高频方向移动，超晶格阱层光致发光峰的压力系数为５９．８ｍｅＶ／ＧＰａ．与（ＣｄＳｅ）ｍ／（ＺｎＳｅ）ｎ短周期超晶格共振时的类ＺｎＳｅ１ＬＯ声子模频率比与ＺｎＳｅ势垒层共振时的类ＺｎＳｅ１ＬＯ声子模频率低２．０ｃｍ－１，反映了（ＣｄＳｅ）ｍ／（ＺｎＳｅ）ｎ短周期超晶格中ＬＯ声子的限制效应