Regenerated fibre Bragg grating fabricated on high germanium concentration photosensitive fibre for sensing at high temperature

A Regenerated Fibre Bragg Grating (RFBG), with repeatable high temperature response between 400 °C–1200 °C, has been demonstrated using a hydrogen-loaded, highly germanium-doped, photosensitive fibre. A wavelength shifts of as much as 20 nm is attained during temperature calibration up to 1300 °C. A large temperature response of 17 pm/°C is obtained from the RFBG, with very good repeatability.     

Critical concentration for metallization of doped germanium and silicon

An elementary model for the metal-non metal transition in n-type Ge and Si is considered. The model is based on recent theoretical work on electron-hole droplets in illuminated semiconductors. The energy of the metallic phase is computed from experimentally known values of the conduction band effective masses and the background dielectric constant. The critical concentration is determined approximately by comparing the energy of the metallic phase with the energy of an isolated donor atom (a bound electron-impurity ion pair). The theoretical estimates of the critical concentration agree in order of magnitude with experiments. The trend in chemical shifts is reproduced.     

AlGaN nanostructures with extremely high quantum yield at 300 K

Theoretical optimization of a quantum well heterostructure based on AlGaN solid solutions is implemented in order to attain the maximum charge carrier activation energy and the maximum exciton binding energy at a radiation wavelength of ~300 nm. An optimized structure sample with the radiative recombination dominating over the temperature range of 5 to 300 K and the room temperature internal quantum yield as high as 80% of the value measured at 5 K has been manufactured via plasma-assisted molecular beam epitaxy.     

Structural and optical properties of metastable SiGe/Si films with a low germanium concentration

The properties of metastable Si_{1 ? x} Ge _x /Si (10% < x < 16%) layers grown by molecular beam epitaxy on Si(100) substrates have been investigated using atomic force microscopy, X-ray diffraction, and low-temperature luminescence spectroscopy. It has been shown that ring-like aggregates are formed on the surface of layers grown at temperatures of 500–700°C. The size and shape of these aggregates suggest that their formation is associated with the diffusion instability arising due to the existence of a relationship between the surface diffusion, stresses, and the wetting potential during the growth of the epitaxial film. The existence of deviations from the homogeneous germanium distribution in the layer plane has been confirmed by a detailed analysis of the X-ray rocking curves and two-dimensional diffraction patterns. The structures with severe surface disturbances are characterized by an abnormal change in the decay times of the emission lines of bulk silicon, which indicate the presence of local electric and/or strain fields in subsurface regions. The perturbations of the flat crystallization front are suppressed as the growth temperature of layers decreases to 350°C. Despite the absence of a coating layer of silicon, the photoluminescence spectra of the layers themselves depend weakly on their thickness and growth temperature and remain sensitive only to the technological concentration of germanium. A slowly decaying luminescence associated presumably with the localization of excitons near the SiGe-Si interface has been observed in one of the samples grown at a temperature of 700°C and containing a dense array of ring-like aggregates.     

Electron-hole droplets in germanium in the high stress limit

We have observed electron-hole droplets in germanium stressed uniformly in the <111> direction to the high stress limit. The measured values of the density, binding energy and phase diagram are in good agreement with theoretical calculations.     

Inelastic electron scattering observation using energy filtered transmission electron microscopy for silicon -- germanium nanostructures imaging

This paper presents a new technique using energy filtered TEM (EFTEM) for inelastic electron scattering contrast imaging of Germanium distribution in Si-SiGe nanostructures. Comparing electron energy loss spectra (EELS) obtained in both SiGe and Si single crystals, we found a spectrum area strongly sensitive to the presence of Ge in the range [50-100 eV]. In this energy loss window, EELS spectrum shows a smooth steeply shaped background strongly depending on Ge concentration. Germanium mapping inside SiGe can thus be performed through imaging of the EELS background slope variation, obtained by processing the ratio of two energy filtered TEM images, respectively, acquired at 90 and 60 eV. This technique gives contrasted images strongly similar to those obtained using STEM Z-contrast, but presenting some advantages: elastic interaction (diffraction) is eliminated, and contrast is insensitive to polycrystalline grains orientation or specimen thickness. Moreover, since the extracted signal is a spectral signature (inelastic energy loss) we demonstrate that it can be used for observation and quantification of Ge concentration depth profile of SiGe buried layers.     

高纯锗中浅受主的光热电离光谱

在液氦温度附近, 运用傅里叶变换光谱以及与之相连的磁光光谱系统, 对室温电阻率约为50Ω·cm的p型高纯锗样品进行了高灵敏度的光热电离光谱的研究.从实验上确定了高纯锗样品中浅杂质光热电离的最佳温度范围, 在该温度范围内测量了样品的光热电离光谱, 指出该样品中主要杂质为浅受主硼与铝. 对杂质谱线发生分裂的两种原因, 补偿性杂质导致的快速复合以及随机应力等, 进行了分析讨论. 关键词： 高纯锗 光热电离光谱 元素半导体中的杂质和缺陷能级     

Raman scattering in germanium at high pressure: Isotope effects

The first-order Raman scattering in isotopically enriched samples of germanium ⁷⁰Ge, ⁷²Ge, and ⁷⁴Ge and germanium with the natural isotopic composition is investigated at high pressures. It is found that the isotopic dependence of the frequency of the LTO(Γ) mode in isotopically pure germanium samples can be described in the harmonic approximation (ν∝m ^−1/2). At the same time, the frequency of the LTO(Γ) mode of germanium of natural isotopic composition apparently contains a contribution due to isotopic disorder effects. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 211–214 (10 February 1999)     

LEED studies of clean high Miller index surfaces of germanium

Clean high Miller index Ge surfaces the poles of which lie on the sides of a unit stereographic triangle were studied by LEED. Clean surfaces of germanium may coincide with the atomic planes of the same indices or consist of the regular steps with (111) or (100) terraces, or contain the “hill and valley” configuration depending on the orientation. Surface atomic planes are reconstructed. On clean Ge surfaces at certain temperatures the reversible order-disorder and order-order transitions take place.     

The excitonic spectrum of germanium in a high magnetic field

In recently reported experiments with uniaxially deformed germanium in a magnetic field [V. B. Timofeev and A. V. Chernenko, JETP Lett. 61, 617 (1995)], it was found that applying a magnetic field of sufficiently high intensity results in the appearance of a new line in the optical spectrum of the excitons. In the present paper a mechanism is proposed which can provide an explanation for this experimentally observed spectral feature. The new spectral line may be attributed to the formation of strongly bound biexcitonic molecules in the quantum state ³Π_u. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 405–409 (25 March 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Fabrication and testing of high quality small germanium plano-convex lens

In this paper, a new method is designed which is accurate (λ/4, λ=632·8 nm) for finishing the small (less than 2·6 mm diameter and a center thickness of 0·4 mm) and soft germanium plano-convex lens. Special features of this process are as follows: (i) it produces a scratch-free and smooth surface; (ii) a precision blocking jig has been constructed which enables the operators to engage centering work of the plano-convex lenses (i.e. the lenses edge are co-axial with the optical axis); (iii) a modified moiré technique rapidly performs the centering test; and (iv) the simulation model has been developed for evaluating the polishing parameters used in this process.     

高纯锗中浅受主的光热电离光谱

在液氦温度附近, 运用傅里叶变换光谱以及与之相连的磁光光谱系统, 对室温电阻率约为50Ω·cm的p型高纯锗样品进行了高灵敏度的光热电离光谱的研究.从实验上确定了高纯锗样品中浅杂质光热电离的最佳温度范围, 在该温度范围内测量了样品的光热电离光谱, 指出该样品中主要杂质为浅受主硼与铝. 对杂质谱线发生分裂的两种原因, 补偿性杂质导致的快速复合以及随机应力等, 进行了分析讨论.     

Biomimetic compound eye with a high numerical aperture and anti-reflective nanostructures on curved surfaces

Biomimetic compound eyes with a high numerical aperture on a curved surface were successfully fabricated by intelligent integration of traditional top-down and bottom-up micro- and nanofabrication methods together. In addition, the new hybrid micro- and nanofabrication method allows us to fabricate the antireflective nanostructures on each ommatidium to increase its vision sensitivity by improving the light transmission. The fabricated compound eye was optically characterized and was shown to have a numerical aperture of 0.77 for each ommatidium. Furthermore, it is shown that the transmission of the compound eye can be improved by 2.3% for the wavelength of 632.8 nm and a clearer image can be formed by the fabricated compound eye with antireflective nanostructures compared with that without antireflective nanostructures. In addition, the developed hybrid manufacturing method can be adapted to the fabrication of other complex micro- and nanodevices for photonics or other research areas.     

高迁移率Ge沟道器件研究进展

高迁移率Ge沟道器件由于其较高而且更对称的载流子迁移率, 成为未来互补型金属-氧化物-半导体(CMOS) 器件极有潜力的候选材料. 然而, 对于Ge基MOS器件, 其栅、源漏方面面临的挑战严重影响了Ge基MOS 器件性能的提升, 尤其是Ge NMOS器件. 本文重点分析了Ge基器件在栅、源漏方面面临的问题, 综述了国内外研究者们提出的不同解决方案, 在此基础上提出了新的技术方案. 研究结果为Ge基MOS 器件性能的进一步提升奠定了基础.     

Electron-density distribution in diamond,silicon and germanium under high pressure

The valence-electron densities of C, Si, and Ge under high pressure are studied with the full-potential linearized APW method. For all three materials, the forbidden x-ray structure factor F(222) is stable under pressure and varies less than 3% under volume changes as big as ± 10%. The 30% drop of F(222) recently measured in Si just before the transition to the β - Sn structure is interpreted as an effect of the coexistence of the diamond and β - Sn phases over a 10 Kbar pressure range centered at the transition pressure.     

A high responsivity,low-noise germanium bolometer for the far infrared

A p-type compensated germanium bolometer operating at 0.1 K is found to have a responsivity of 2.8×10⁷ V/W and an estimated limiting NEP of 3x10^-16 W/(Hz)^{$\text{1}\text{2}$}.     

Imprinting the nanostructures on the high refractive index semiconductor glass

The centimeter range one- and two-dimensional nanostructures of 70 nm pitch have been imprinted by hot pressing with a quartz, silicon or nickel mold, at 240 °C, onto the surface of Ge₂₀As₂₀Se₁₄Te₄₆ semiconductor glass. Excellent glass stability of this glass allows multiple re-pressing of the nano-structures. With increasing the Te/Se ratio in the glass formula, the refractive index reaches a value of 3.5 with an option of free electron absorption at elevated temperatures pointing out the use of such nanostructures in submicron and micron scale electronic devices/chips, moth eye structures and photonic crystals.     

Behavior of copper in gallium arsenide with high tin concentration

Investigations were made of the electrical properties, the cathodolumiescence and photoconductivity spectra, and the temperature dependence of the majority carrier lifetime in gallium arsenide with a high concentration of tin (n=2·10¹⁸ cm^–3, 1.5·10¹⁷ cm^–3) that was doped with copper under different diffusion regimes. Measurements of the Hall effect revealed centers with an ionization energy 0.175 ± 0.005 eV, their concentration depending on the rate of cooling of the samples. The cathodoluminescence and Hall effect data suggest that the cathodoluminescence band observed at 1.35 eV in GaAsSnCu is associated with radiative transitions of electrons to centers with _a =E_v + 0.175 eV. The hole lifetime in GaAsSnCu has a complicated temperature dependence which can be explained qualitatively by the presence of two types of capture center.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 58–63, September, 1980.     

单光束互相关法测量高浓度纳米颗粒粒径

针对光子相关光谱法不能测量高浓度纳米颗粒粒径和双光束互相关测量法装置结构过于复杂等问题,提出了一种基于范西特-泽尼克定理的单光束互相关法。首先分析了传统双光束互相关法存在的问题,然后根据范西特-泽尼克定理建立了单光束互相关测量法的模型,设计完成了单光束互相关颗粒粒度测量装置,最后对各种浓度不同粒径的颗粒进行了测量。实验证明,单光束互相关法能有效抑制多重散射的影响,适用于测量高浓度纳米颗粒粒径。