Interimpurity light absorption in thin wires of III-V-type semiconductors

A study has been performed of interimpurity light absorption in weakly doped thin wires of III–V type semiconductors with Kane charge-carrier dispersion law with the one-dimensional random distribution of the impurities taken into account. The dependence of the absorption curve is analyzed: the location of the absorption maxima corresponding to transitions from the acceptor ground level to the ground level and first excited level of the donor as well as their edges and half-widths are found. It is shown that the nonparabolicity of the charge-carrier dispersion law leading to transitions between the impurity ground states causes an abrupt detachment of this absorption line from the remaining lines. Fiz. Tekh. Poluprovodn. 32, 108–110 (January 1998)     

杂质对掺钕磷酸盐激光玻璃光谱性质的影响

综述了过渡金属杂质（Cu,Fe）和稀土杂质（Dy,Pr,Sm,Ce）对掺钕磷酸盐激光玻璃吸收损耗及Nd^3＋荧光猝灭影响的研究状况。     

Magneto-absorption of donor impurities in quantum-well wires

We show calculations for far-infrared absorption of shallow-donor impurities in quantum well wires in the presence of an external magnetic field. The wave functions and the eigenvalues are obtained in the effective-mass approximation by using an extended variational approach in which the ground and excited magneto-impurity states are simultaneously obtained. We investigate the allowed intra-donor transitions for radiation circularly polarized in the plane perpendicular to the magnetic field. We present results for the absorption coefficient as a function of the photon energy for several field strengths and arbitrary impurity positions.     

InAs Nanocrystals with Robust p-Type Doping

Robust control over the carrier type is fundamental for the fabrication of nanocrystal-based optoelectronic devices, such as the p–n homojunction, but effective incorporation of impurities in semiconductor nanocrystals and its characterization is highly challenging due to their small size. Herein, InAs nanocrystals (NCs), post-synthetically doped with Cd, serve as a model system for successful p-type doping of originally n-type InAs nanocrystals, as demonstrated in field effect transistors (FETs). Advanced structural analysis, using atomic resolution electron microscopy and synchrotron X-ray absorption fine structure spectroscopy reveal that Cd impurities reside near and on the nanocrystal surface acting as substitutional p-dopants replacing Indium. Commensurately, Cd-doped InAs FETs exhibit remarkable stability of their hole conduction, mobility, and hysteretic behavior over time when exposed to air, while intrinsic InAs NCs FETs are easily oxidized and their performance quickly declines. Therefore, Cd plays a dual role acting as a p-type dopant, and also protects the nanocrystals from oxidation, as evidenced directly by X-ray photoelectron spectroscopy measurements of air exposed samples of intrinsic and Cd-doped InAs NCs films. This study demonstrates robust p-type doping of InAs nanocrystals, setting the stage for implementation of such doped nanocrystal systems in printed electronic devices.     

基于隐变量模型的语音转换方法研究

传统语音转换方法利用说话人声音特征映射实现,容易造成过平滑（over-smoothing）和过拟合（over-fitting）问题。本文从语音信号内容与形式分离角度,利用隐变量模型提出了一种全新的语音转换方法。首先利用包含两个隐变量因子的隐变量模型（Latent Variable Model, LVM）建立语音信号的生成模型;然后采用最大似然方法把语音信号分解成表示语义的内容信息和体现说话人特征的形式信息,并估计出模型参数;最后基于LVM生成模型,利用说话人形式替换方法实现语音转换。主、客观测试结果表明,在相同训练集条件下,本文提出的语音转换方法性能明显优于GMM方法,并且隐变量模型和传统的双线性模型（Bilinear Model）相比,由于采用非线性关系描述内容与形式之间的相互作用,因此分离效果更好,语音转换质量更高。      

Impurity segregation in horizontal bridgman grown cadmium zinc telluride

Segregation of impurities that cause low infrared (IR) transmission in horizontal Bridgman (HB) grown cadmium zinc telluride (CdZnTe) has been investigated. This segregation was characterized using IR transmission, glow discharge mass spectrometry (GDMS), and IR microscopy measurements. In the studied HB CdZnTe ingots, impurity segregation causes the formation of a small volume in the last-to-freeze portion of the ingot that has high impurity concentration and low IR transmission. Outside this region the concentration of impurities is low and the material shows high IR transmission. The region is visibly observable on CdZnTe slices and appears as a dark area with a sharp boundary. Free carrier absorption within the region causes a decrease in IR transmission with an increase in wavelength and correlates with the concentration of lithium and sodium impurities. Impurity segregation in HB ingots is described and explains the location of the high impurity region. The location of the visible boundary correlates with the first measurable change in IR transmission as compared to the high IR transmission of the surrounding material and supports the hypothesis that the darkening of the region is due to a reduction of the reflectivity due to free carrier absorption. With a properly controlled cool-down recipe, the impurities segregated in the last-to-freeze section of the ingots can remain localized, thereby improving the purity of the remaining bulk of the material.     

Microwave Magnetic Absorption in HgSe with Co and Ni Impurities

Semiconductors - Features of magnetic-field-dependent microwave absorption in HgSe samples doped with Co and Ni impurities in different concentrations are investigated. The electron-spin resonance...     

氢钝化对Hg1—xCdxTe红外透射谱的影响

采用红外透射测量观测了氢钝化对Ｈｇ１－ｘＣｄｘＴｅ晶片的影响，用分层模型计算了晶片射率，分析了氢钝化增加其透射率，吸收边向短波方向移动，低于禁带宽度能量的吸收降低，透过范围减小的原因。表明氢钝化不仅影响到表面，而且影响到整个体内。原因是经氢钝化处理后杂质或缺陷受到有效钝化，载流子浓度降低，组分Ｘ增加；荷电杂质或缺陷的局域内场影响发失变化；以及荷电杂质或缺陷散射增强。     

Low-loss fluoride optical fibers for midinfrared optical communication

Attempts to improve transmission loss characteristics in fluoride fibers are described. Optical loss in current fibers is dominated by two major extrinsic loss factors, defect scatterers and impurities. Scatterer analysis using a Raman microprobe has revealed that the majority of them are ZrO2crystallites. These crystallites dominate the fiber scattering characteristics, having both wavelength independent and Rayleigh wavelength^-4dependencies according to their size. Excess loss due to OH groups which causes absorption at around 2.9 μm is quantified as 2000-5000 dB/km/ppm, depending on glass composition. These results suggest that further efforts in glass synthesis should concentrate on eliminating oxide and hydroxide impurities, and on the further purification of the raw materials. The key for realizing high-quality, low-loss, and long-length fluoride fibers is currently related to whether or not oxide scatterers can be completely eliminated.     

Infrared absorption spectrum of neutral magnesium donors in silicon

The infrared absorption spectrum of neutral magnesium donor impurities in silicon has been investigated under the high resolution of a Fourier-transform infrared spectrometer. The absorption spectrum measured at liquid helium temperature are observed to be clearly better than those reported earlier in the literature. Several new lines corresponding to excitation from ground state to higher excited states have been observed and identified.     

Excited states of chalcogen ions in germanium

The energy spectra of chalcogen impurities in germanium are studied by photoconductivity, optical absorption, and photoluminescence. The previously found excited states of these impurities are identified. The observed excited states of tellurium (Te⁺) and selenium (Se⁺) ions are shown to be associated with the Γ and L points of the germanium Brillouin zone, respectively. Fiz. Tekh. Poluprovodn. 32, 155–158 (February 1998)     

不同工艺条件下TiO2单层膜的吸收和损伤阈值测试

利用电子束热蒸发技术在不同氧分压和烘烤温度下镀制了一系列TiO2单层膜,采用表面热透镜技术测量了样品在1064nm处的弱吸收值,并用激光损伤测试平台测量了样品的抗激光损伤阈值(LIDT)特性。实验结果表明较高的氧分压和较低的烘烤温度能显著减小薄膜的吸收值。不过薄膜在基频下的损伤阈值除了受到薄膜吸收值的影响外,还取决于基底表面的杂质密度,当薄膜吸收较大时,本征吸收对损伤破坏起到主要作用;随着薄膜的吸收逐渐减小,基底表面处的缺陷吸收逐渐取代本征吸收成为影响薄膜损伤阈值的主导因素。     

水晶的缺陷与品质鉴定

介绍了人工水晶的缺陷与品质鉴定；讨论了缺陷的种类和各种缺陷对晶体质量的影响，以及杂质在晶体中的分布和晶体结构之间的关系。对晶体质量的鉴定主要是通过红外吸收谱和干涉仪检查及Ｘ射线形貌术来完成的。     

Synthesis and Performance of BaAl2O4 with a Wide Spectral Range of Optical Absorption

Oxygen‐deficient BaAl₂O₄, with strong optical absorption in the spectra range from 200 to 2500 nm, was prepared by a simple and economic thermal treatment of BaAl₂O₄ in a H₂ gas flow. Further studies found that a molar ratio of oxygen vacancies of about 0.4 % existed in the prepared oxygen‐deficient BaAl₂O₄ sample. The influence of oxygen vacancies on the electronic band structures and optical absorption of BaAl₂O₄ are elucidated via first principle calculations. Oxygen vacancies introduce impurity states above the valence band; these impurities expand and enhance the optical absorption of BaAl₂O₄. This approach is proposed to develop a new type of optical materials and to be applicable to many wide bandgap materials.     

A study of the photothermal effect induced by an ir laser impulse

In this article, we study the spatial and temporal IR distribution of the temperature in an absorbant material, while periodically exposing it to IR luminescent radiation. We compare our results with those obtained experimentally from semiconductor materials. An understanding of the form of the signal permits us to determine the ratio of the penetration depth of the IR radiation to the thermal diffusion length into the material. In the case of weak concentration of absorbant impurities in a homogeneous material, the thermal properties are slightly modified and absorption is proportional to concentration. With this method, we satisfactorily found it possible to determine the rate of the impurities distributed in the material.     

平面型InGaAs探测结构中p型杂质的二维扩散行为研究

在平面型InGaAs P-i-N短波红外探测结构中,p型杂质在材料中纵向和横向的扩散是决定pn结位置及其光电性能的主要因素,本文采用扫描电容显微方法(SCM)获得了扩散成结InGaAs/InAlAs像元剖面的二维载流子分布,从而实现对不同扩散条件下pn电场结的精确定位和分析.此外,对于InGaAs/InP探测器,SCM...     

金刚石薄膜的红外吸收谱研究

研究了热丝CVD金刚石薄膜的红外反射吸收谱,讨论了金刚石薄膜中H、N等杂质和晶粒晶型、晶粒尺度对膜红外透过率的影响。     

Revealing the Atomic Defects of WS2 Governing Its Distinct Optical Emissions

Defects and their spatial distribution are crucial factors in controlling the electronic and optical properties of semiconductors. By using scanning transmission electron microscopy and electron energy loss spectroscopy, the type of impurities/defects in WS₂ subdomains with different optical properties is successfully assigned. A higher population of Cr impurities is found in the W‐terminated edge domain, while the S‐terminated domain contains more Fe impurities, in accordance with the luminescence characteristics of chemical‐vapor‐grown WS₂ of a hexagonal shape. In agreement with the first‐principles calculations, the domains with Cr substitutional dopants exhibit strong trion emission. Fe atoms tend to gather into trimer configuration and introduce deep acceptor levels which compensate the n‐type doping and suppress trion emission. It is also discovered that the domain with higher luminescence but smaller defect concentration tends to get oxidized more rapidly and degrade the 2D structure with many triangular holes. Excitons tend to accumulate at the edges of the oxidized triangular holes and results in enhanced PL emission. The findings indicate that choosing stable elements as dopant and controlling the number of specific edge structures within a crystal domain of 2D transitional metal dichalcogenides can be a new route to improve the optical properties of these materials.     

CdZnTe substrate impurities and their effects on liquid phase epitaxy HgCdTe

Impurity levels were tracked through the stages of substrate and liquid phase epitaxy (LPE) layer processing to identify sources of elements which degrade infrared photodetector performance. Chemical analysis by glow discharge mass spectrometry and Zeeman corrected graphite furnace atomic absorption effectively showed the levels of impurities introduced into CdZnTe substrate material from the raw materials and the crystal growth processes. A new purification process(in situ distillation zone refining) for raw materials was developed, resulting in improved CdZnTe substrate purity. Substrate copper contamination was found to degrade the LPE layer and device electrical properties, in the case of lightly doped HgCdTe. Anomalous HgCdTe carrier type conversion was correlated to certain CdZnTe and CdTe substrate ingots.     

Effect of doping with gadolinium on the physical properties of Hg3In2Te6

Special features of gadolinium solubility during the Hg₃In₂Te₆:Gd crystal growth are considered. The highest attainable gadolinium concentration in the solid phase is equal to 2.3×10¹⁹ cm^?3. It is shown that, as the doping level increases, strains and stresses in the crystal lattice occur and correlate with the dopant concentration. Doping has virtually no effect on the transport properties and the Fermi level located near the middle of the energy gap. The optical absorption observed at photon energies lower than the energy gap is accounted for by the tails of the density of states in the band gap. Absorption-spectra features are explained using the theory of the interaction of light with disordered, heavily compensated semiconductors. Additional structureless absorption in the optical transparency region is caused by the small-angle scattering of light by inclusions formed by the charged impurities.