Determination of doping effects on Si and GaAs bulk samples properties by photothermal investigations

The knowledge of doping effects on optical and thermal properties of semiconductors is crucial for the development of opto-electronic compounds. The purpose of this work is to investigate these effects by mirage effect technique and spectroscopic ellipsometry SE.

The near gap optical spectra are obtained from photothermal signal for differently doped Si and GaAs bulk samples. However, the above bandgap absorption is determined from SE. These spectra show that absorption in the near IR increases with dopant density and also the bandgap shifts toward low energies. This behavior is due to free carrier absorption which could be obtained by subtracting phonon-assisted absorption from the measured spectrum. This carrier absorption is related to the dopant density through a semi-empirical model.

We have also used the photothermal signal phase to measure the influence of doping on thermal diffusivity.     

掺杂Si/SiO_2界面电子结构与光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,在局域密度近似(LDA)下研究了B掺杂Si/SiO_2界面及其在压强作用下的电子结构和光学性质.能带的计算结果表明:掺杂前后Si/SiO_2界面均属于直隙半导体材料,但掺B后界面带隙由0. 74 eV减小为0. 57 eV,说明掺B使材料的金属性增强;对B掺杂Si/SiO_2界面施加正压强,发现随着压强不断增大,Si/SiO_2界面的带隙呈现了逐渐减小的趋势,并且由直隙逐渐转变为间隙.光学性质的计算结果表明:掺B对Si/SiO_2界面在低能区(即红外区)的介电函数虚部、吸收系数、折射率以及反射率等光学参数有显著影响,且在红外区出现新的吸收峰;对B掺杂Si/SiO_2界面施加正压强,随着压强增大,红外区的吸收峰逐渐消失,而在紫外区出现了吸收峰.上述结果表明,对Si/SiO_2界面掺B及施加正压强均可调控Si/SiO_2界面的电子结构与光学性质.本文的研究为基于Si/SiO_2界面的光电器件研究与设计提供一定的理论参考.     

Optical and thermal properties of doped semiconductor

The knowledge of doping effects on optical and thermal properties of semiconductors is crucial for the development of optoelectronic compounds. The purpose of this work is to investigate theses effects by mirage effect technique and spectroscopic ellipsometry SE. The absorption spectra measured for differently doped Si and GaAs bulk samples, show that absorption in the near IR increases with dopant density and also the band gap shifts toward low energies. This behavior is due to free carrier absorption which could be obtained by subtracting phonon assisted absorption from the measured spectrum. This carrier absorption is related to the dopant density throw a semi-empirical model.     

Effect of isotope doping on phonon thermal conductivity of silicene nanoribbons: A molecular dynamics study

Silicene, a silicon analogue of graphene, has attracted increasing research attention in recent years because of its unique electrical and thermal conductivities. In this study, phonon thermal conductivity and its isotopic doping effect in silicene nanoribbons(SNRs) are investigated by using molecular dynamics simulations. The calculated thermal conductivities are approximately 32 W/mK and 35 W/mK for armchair-edged SNRs and zigzag-edged SNRs, respectively, which show anisotropic behaviors. Isotope doping induces mass disorder in the lattice, which results in increased phonon scattering, thus reducing the thermal conductivity. The phonon thermal conductivity of isotopic doped SNR is dependent on the concentration and arrangement pattern of dopants. A maximum reduction of about 15% is obtained at 50% randomly isotopic doping with ~(30)Si. In addition, ordered doping(i.e., isotope superlattice) leads to a much larger reduction in thermal conductivity than random doping for the same doping concentration. Particularly, the periodicity of the doping superlattice structure has a significant influence on the thermal conductivity of SNR. Phonon spectrum analysis is also used to qualitatively explain the mechanism of thermal conductivity change induced by isotopic doping. This study highlights the importance of isotopic doping in tuning the thermal properties of silicene, thus guiding defect engineering of the thermal properties of two-dimensional silicon materials.     

第一性原理研究B掺杂Mn_4Si_7的电子结构和光学性质

采用基于密度泛函理论的第一性原理计算方法,对未掺杂及B掺杂Mn_4Si_7的电子结构和光学性质进行理论计算.研究结果表明,未掺杂Mn_4Si_7是间接带隙半导体,其禁带宽度为0.786 eV,B掺杂后其禁带宽度下降为0.723 eV. B掺杂Mn_4Si_7是p型半导体材料.未掺杂Mn_4Si_7在近红外区的吸收系数达到10~5 cm~(-1),B掺杂引起Mn_4Si_7的折射率、吸收系数、反射系数及光电导率增加.     

Ge，Al掺杂锰硅化合物Mn4Si7的第一性原理计算

基于密度泛函理论（DFT）的第一性原理计算方法,对本征Mn4Si7以及Ge,Al单掺杂和共掺杂Mn4Si7的晶体结构,能带结构,态密度以及光学性质进行了计算和分析.计算结果表明：本征态Mn4Si7的禁带宽度为0.810 eV,为直接带隙半导体材料,掺杂后晶体结构稍微变化,禁带宽度减小,且共掺杂时禁带宽度最小,电导率最好.Al以及Ge,Al共同掺杂时会产生杂质能级.掺杂后光子能量向低能级方向移动,光电导率,光吸收,反射系数都有所增大,说明掺杂改善了Mn4Si7的光学性质,从而可以提高光伏发电效率.     

Problems of homogeneous irradiation of Si ingots more than 200 mm in diameter under neutron doping

The problem of homogeneous irradiation of Si ingots of large diameter (i.e., comparable with the thermal neutron diffusion length in silicon—20 cm) by thermal neutrons is considered. The effect of neutron absorption on the irradiation homogeneity is discussed. It is established for some usual cases of neutron doping that the neutron distribution in the irradiation zone affects the irradiation homogeneity. The results obtained can be useful for choosing and designing the irradiation zone for neutron doping of silicon.     

Effect of Si doping on GaN/AlN multiple-quantum-well structures for intersubband optoelectronics at telecommunication wavelengths

We present a study of the effect of Si doping localization on the optical and structural properties of GaN/AlN multiple-quantum-well structures for intersubband (ISB) absorption at 1.55 μm. Samples were either undoped or Si doped in different regions (barrier, quantum well (QW), middle of barrier or middle of QW). Structural characterization by atomic force microscopy and X-ray diffraction does not show significant differences in the crystalline quality. All doped samples present room-temperature p-polarized ISB absorption of about 1%–2% per pass, with a line width of 80–90 meV. In contrast, undoped samples present a weaker ISB absorption with a record line width of 40 meV. Both photoluminescence (PL) and ISB absorption display structured shapes whose main peaks correspond to monolayer fluctuations of the well thickness. The emission and absorption line widths depend on the Si doping concentration, but not on the Si location.     

Cr掺杂以及Mo和Cr双掺Mn4Si7的第一性原理计算

采用基于密度泛函理论中第一性原理的赝势平面波法,分别对本征Mn4Si7、Cr掺杂Mn4Si7以及Cr和Mo双掺Mn4Si7的电子结构及光学性质进行了计算和分析。计算结果表明本征Mn4Si7禁带宽度为Eg=0.813 eV,Cr掺杂Mn4Si7禁带宽度为Eg=0.730 eV,Cr和Mo双掺Mn4Si7禁带宽度为Eg=0.620 eV,均为间接带隙半导体、p型掺杂。此外,在低能区掺杂体系的介电函数、折射率、消光系数、吸收系数以及光电导率均强于本征Mn4Si7,表明Cr掺杂Mn4Si7以及Cr和Mo双掺Mn4Si7有运用于红外光电子器件的巨大潜力。     

Thermal conductivity of symmetrically strained Si/Ge superlattices

This paper reports temperature-dependent thermal conductivity measurements in the cross-plane direction of symmetrically strained Si/Ge superlattices, and the effect of doping, period thickness and dislocations on the thermal conductivity reduction of Si/Ge superlattices. The Si/Ge superlattices are grown by molecular beam epitaxy on silicon and silicon-on-insulator substrates with a graded buffer layer. A differential 3 ω method is used to measure the thermal conductivity of the buffer and the superlattices between 80 and 300 K. The thermal conductivity measurement is carried out in conjunction with X-ray and TEM sample characterization. The measured thermal conductivity values of the superlattices are lower than those of their equivalent composition bulk alloys.     

Mg2Si的电子结构和热电输运性质的理论研究

利用全势线性缀加平面波法,对Mg₂Si的几何结构和电子结构进行了计算,得到了稳定的晶格参数以及能带和电子态密度.能带结构表明,Mg₂Si为间接带隙半导体,禁带宽度为020 eV.在此基础上利用玻尔兹曼输运理论和刚性带近似计算了材料的电导率、Seebeck系数和功率因子.结果表明,在温度为700 K时p型和n型掺杂的Mg₂Si功率因子达到最大时的最佳载流子浓度分别为7749×10¹⁹ cm^-3和 关键词： 2Si')" href="#">Mg₂Si 全势线性缀加平面波法 热电输运性质     

Investigation of the microstructure and properties of doped nanocomposite coatings based on titanium nitride

The special features of the elemental composition, structure-phase and elastically stressed states, and properties of coatings based on titanium nitride are investigated for different concentrations of Al, Si, Cu, Ni, Cr, and C doping elements using x-ray fluorescent analysis, x-ray microanalysis, dark-field electronmicroscopic analysis of the crystal lattice bending and torsion, microhardness measurements, and scratch tests. Influence of the structure and concentration of the doping elements on the relative fraction of nonmetallic atoms, crystal size, and phase composition of the coating is established. High values (several hundred degrees per micron) of the lattice bending-torsion with dipole configuration are established for nanocrystals with sizes smaller than 20 nm. Residual stresses in nanocrystals are estimated for the disclination model of the structural state. It is demonstrated that the increased degree of coating doping improves the thermal stability of their structure and properties.     

Yb∶YAG晶体的荧光特性研究

测量了不同掺杂浓度Yb∶YAG晶体氧化和还原气氛退火前后的色心吸收光谱、荧光光谱和荧光寿命.研究了色心对Yb∶YAG晶体的荧光强度和荧光寿命的影响.结果表明,只有当Yb的掺杂浓度大于10 at.%时,色心吸收的加强对发光强度和荧光寿命有明显猝灭作用.     

Optical properties of Si-rich SiO2 films in relation with embedded Si mesoscopic particles

Optical properties of Si-rich SiO₂ films prepared by an RF cosputtering method are discussed. From the infrared and Raman spectroscopy together with the electron microscopy, it is shown that Si mesoscopic particles embedded in solid matrices with the sizes ranging from ˜ 10 nm (nanocrystals) to less than ˜1 nm (clusters) can be obtained by the cosputtering and post-annealing. The absorption and photoluminescence spectra are presented. For our samples, a red luminescence peak analogous to that of porous Si is observed for films containing Si clusters rather than nanocrystals. Raman spectra which evidence the success in the heavy doping of B atoms into Si nanocrystals are also discussed.     

快速退火后重掺硼的分子束外延层的电学特性

对快速退火后用共蒸发Ｂ_２Ｏ₃方法实现重掺杂硼的硅分子束外延层的电学特性进行了研究．１１００℃退火可以使得外延层中载流子浓度提高４倍，空穴的霍耳迁移率与相同浓度下硅体材料的水平相当；外延层与衬底之间载流子浓度转变陡峭，获得了晶体质量良好的外延层． 关键词：     

Effects of Si doping on the structural and electrical properties of Ge2Sb2Te5 films for phase change random access memory

The effects of Si doping on the structural and electrical properties of Ge₂Sb₂Te₅ film are studied in detail. Electrical properties and thermal stability can be improved by doping small amount of Si in the Ge₂Sb₂Te₅ film. The addition of Si in the Ge₂Sb₂Te₅ film results in the increase of both crystallization temperature and phase-transition temperature from face-centered cubic (fcc) phase to hexagonal (hex) phase, however, decreases the melting point slightly. The crystallization activation energy reaches a maximum at 4.1 at.% and then decreases with increasing dopant concentration. The electrical conduction activation energy increases with the dopant concentration, which may be attributed to the increase of strong covalent bonds in the film. The resistivity of Ge₂Sb₂Te₅ film shows a significant increase with Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460 °C annealing increases from 1 to 11 mΩ cm compared to the undoped Ge₂Sb₂Te₅ film. Current-voltage (I-V) characteristics show Si doping may increase the dynamic resistance, which is helpful to writing current reduction of phase-change random access memory.     

Influence of the Production Technology on the Optical Properties and Radiation Stability of TiO2 Pigments (Anatase)

The fluoride technology of producing the titanium dioxide pigment with the anatase structure by doping with Mg, Si, and Zn is described. The influence of technological regimes of producing and doping of anatase powders on their reflection and total solar radiation absorption coefficients and their changes after irradiation by electrons with energy of 30 keV are investigated.     

Zn掺杂β-Ga2O3薄膜的制备和特性研究（英文）

β-Ga2O3是一种宽带隙半导体材料,能带宽度Eg≈5.0eV,在光学和光电子学领域有广泛的应用.用射频磁控溅射方法在Si衬底和远紫外光学石英玻璃衬底制备了本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜,用紫外-可见分光光度计、X射线衍射仪、荧光分光光度计对本征β-Ga2O3薄膜及Zn掺杂β-Ga2O3薄膜的光学透过、光学吸收、结构和光致发光进行了测量,研究了Zn掺杂和热退火对薄膜结构和光学性质的影响.退火后的β-Ga2O3薄膜为多晶结构,与本征β-Ga2O3薄膜相比,Zn掺杂β-Ga2O3薄膜的β-Ga2O3(111)衍射峰强度变小,结晶性变差,衍射峰位从35.69°减小至35.66°.退火后的Zn掺杂β-Ga2O3薄膜的光学带隙变窄,光学透过降低,光学吸收增强,出现了近边吸收,薄膜的紫外、蓝光及绿光发射增强.表明退火后Zn掺杂β-Ga2O3薄膜中的Zn原子被激活充当受主.     

Optical properties of Si-doped InAs/InP quantum dots

InAs quantum dots (QDs) were grown on InP substrates by low pressure-metalorganic chemical vapor deposition. Disilane (Si₂H₆) was used as an n-type dopant. The positions of Si doping were varied: buffer layer, capping layer, modulation doping, and QD itself. Surface treatment of InP by Si₂H₆ was also performed to see the effect of Si on InAs QD. Photoluminescence (PL) and atomic force microscopy (AFM) were used to characterize optical and structural properties of QDs, respectively. It was found that the PL peak positions varied from 0.73 to 0.88 eV with the position of Si doping. PL peak blue shift in modulation doped sample was explained in terms of state filling effect. It was found that Si doping at QD itself was the most effective way to obtain the strongest integrated PL intensity without degrading the QD size distribution.     

镍掺杂硅纳米线电子结构和光学性质的第一性原理研究

利用基于密度泛函理论的第一性原理计算,对镍掺杂硅纳米线的结构稳定性、电子与光学性质进行了研究.结果表明:Ni容易占据硅纳米线表面的替代位置.镍掺杂后的硅纳米线引入了杂质能级,杂质能级主要来源于Ni的3d电子的贡献.由于Ni的3d态和Si的3p态的耦合作用,使禁带宽度变窄.掺杂后的硅纳米线在低能区出现了一个较强的吸收峰,且吸收带出现宽化现象. 关键词： 硅纳米线 掺杂 电子结构 光学性质