Papers by Keyword: Ge

Abstract: Doubly-fed induction generator (DFIG) wind turbine has become the most widely used wind turbine in wind farms, since it presents noticeably advantages such as decoupled controls of active and reactive powers, and the use of a power converter with a rated power of 25% of total system power. As the penetration of wind power in power system increases, it is required that the wind turbine remained connected and actively contributed to the system stability during and after faults and disturbance. One common approach for a DFIG to obtain such low voltage ride through (LVRT) function is to install a crowbar circuit across its rotor terminals, which short circuit the rotor side converter when over-current is detected in the rotor. A detailed model of LVRT function normally requires electromagnetic simulations. However, the time consuming computational process is prohibitive for the studies of the integration of wind farms into large scale power systems. Electromechanical simulations are more suitable for such engineering applications. GE has incorporated the LVRT function into its recently released DFIG wind turbine model for Electro-mechanical simulations. This paper has implemented this model and verified the effectiveness of the LVRT function.

Abstract: Since silicon will ultimately face physical limitations, germanium and III-V materials, such as Ga, GaAs, InGaAs, are being extensively investigated for their high electron and hole mobility advantages. Prior to implementing germanium or III-V materials, it is believed that SiGe with high Ge concentration will be applied for channel materials in pMOS devices with high-k and metal gates in order to simultaneously adjust the work function and to increase the hole mobility. However, introduction of new channel materials leads to new challenges and substantial changes in the FEOL process flow.

Abstract: Management Information System (MIS) is an Integration information systems engineering of computer technology and network communications technology. It can be more accurate, timely, comprehensive, detailed record of the data, while further processing of all kinds of information. In this paper, MFC, GPS and GE (Google Earth) technology is used in managing Old and Valuable Trees information, to solve a series of existing problems of labor management. At the same time of improving the efficiency of information management, it can achieve the implementation of monitoring and tree information Virtual Tour by combination in GPS the point marked and Google Earth software.

Abstract: The Ge doped Mn₃CuN powder was synthesized using gas-solid reaction method with manganese, copper, germanium powders and N₂ gas as raw material. The phase constitute of the as-prepared powder was characterized using X-ray diffraction (XRD). The intrinsic and macro thermal expansion coefficients of the powder were measured by in-situ X-ray diffraction at different temperatures and TMA, respectively. The crystal structure of the powders was analyzed using Rietveld refinement method. The results show that the pure Mn₃(Cu_0.5Ge_0.5)N powder can be prepared via the gas-solid method at 850 °C. The crystal structures of Mn₃(Cu_0.5Ge_0.5)N and Mn₃CuN both have the antiperovskite structures. The intrinsic and macro thermal expansion coefficient of Mn₃(Cu_0.5Ge_0.5)N powder is-16.8×10^-6K^-1 and-17×10^-6K^-1, respectively. The temperature range with negative thermal expansion is from-80 °C to 50 °C.

Abstract: An effort has been made to understand the charge density distribution of the Si and Ge based diluted magnetic semiconductors. A theoretical analysis has been done on the variation of charge densities when the semiconductors Si and Ge are doped with the transition metal atoms of V, Mn and Co with different concentrations of x (0.02, 0.04, 0.06, 0.08, and 0.10), in Si_1-xM_x and Ge_1-xM_x. Two dimensional electron density contour maps have been plotted for all the compositions studied in this work. The theoretical mid bond densities were found out for the compounds which can be taken as the reference values for comparison of the experimental values of the same compositions.

Abstract: Selective epitaxial growth of germanium (Ge) on nano-structured Si(001) wafers is studied to evaluate the applicability of the nano-heteroepitaxy (NHE) approach on Ge-Si system. Based on a gate spacer technology established in advanced silicon microelectronics periodic arrays of nano-scaled Si islands are prepared, where Ge is deposited on top by reduced pressure CVD. The spacing of these structures is 360 nm. The structural perfection of the deposited Ge is investigated by transmission electron microscopy and X-ray diffraction. It is found that SiO₂ used as masking material is responsible for the suppression of the desired strain partitioning effect according to NHE. Even for 10 nm oxide thickness, the lattice of Ge layers deposited on Si nano-islands relaxes completely by generation of misfit dislocations at the interface. The occurrence of additional structural defects like stacking faults and micro twins can be controlled by suited growth conditions.

Abstract: We present a novel Ge on Si based LED with unstrained i-Ge active region. The device operates at room temperature and emits photons with energy of 0.8 eV. It basically resembles a p-i-n structure formed on a sub-micrometer thin Ge layer. The Ge layer has been grown on Si substrate by utilizing thin virtual buffer, so it becomes stress free but with high threading dislocation density. We show that such forward biased diode generates strong emission, caused by direct band to band transition in Ge. Using an InSb based detector we were able to analyze the emission spectrum in a broad energy range. We show that at low and moderate currents, features belonging to the direct and the indirect band to band electronic transitions are present which are characteristic for Ge. Clearly dominating is the direct transition related peak. Due to the missing stress-related red shift this peak appears close to the desired communication wave length of 1.55 μm. The dependence of radiation intensity on the excitation current follows a power low with exponent of 1.7, indicating that the recombination rate of the competitive nonradiative processes is relatively low. At high excitation currents features appear in the low energetic part of the spectrum. All results presented here are discussed in view of the outcome from measurements on Ge high quality bulk material. The role of the dislocation in the Ge films is discussed.

Abstract: By using the sol-gel method, TiO₂ thin films and Ge doped TiO₂ composite thin films were fabricated onto quartz substrates. XRD, XPS and UV-vis were used to characterize the phase structure, the atomic chemical states and optical absorption of these composite TiO₂ thin films. XRD results indicate that diffraction peak of anatase is observed in samples. XPS result reveals that there is Ge crystal in Ge doped films which were prepared by sol-gel method, and Ge exists as elemental Ge and GeO₂ in the films. The composite TiO₂ thin films by sol-gel method exhibits the absorption shift to visible region due to Ge doped TiO₂ thin films.

Abstract: Ge doped ZnO films were synthesized on silicon substrate via RF magnetron co-sputtering methods. The effects of annealing temperature on the optical and structural properties of the Ge doped ZnO films were investigated by means of photoluminescence spectra, X-ray diffraction, and X-ray Photoelectron Spectroscopy. The ultra-violet emission should be related with the free-exciton recombination, and blue and yellow emissions should be attributed to the defect state caused by Ge. The varieties of annealing temperature affect greatly the optical properties. The high annealing temperature leads to the oxidation of Ge and the formation of Zn₂GeO₄, which could lead to the change of PL spectra.

Abstract: By low-temperature epitaxial growth of group IV semiconductors utilizing electron-cyclotron-resonance (ECR) plasma enhanced chemical vapor deposition (CVD), atomically controlled plasma processing has been developed in order to achieve atomic-layer doping and heterostructure formation with nanometer-order thickness control as well as smooth and abrupt interfaces. In this paper, typical recent progress in plasma processing is reviewed as follows: (1) By N and B atomic-layer formation and subsequent Si epitaxial growth on Si(100) without substrate heating, heavy atomic-layer doping was demonstrated. Most of the incorporated N or B atoms can be confined in about a 2-nm-thick region of the atomic-layer doped Si film. (2) Using an 84 % relaxed Ge buffer layer formed on Si(100) by ECR plasma enhanced CVD, formation of a B-doped highly strained Si film with nanometer-order thickness was achieved and hole mobility enhancement as high as about 3 was observed in the highly strained Si film.