High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate

Si/Ge uni-traveling carrier photodiodes exhibit higher output current when space-charge effects are overcome and thermal effects are suppressed, which is highly beneficial for increasing the dynamic range of various microwave photonic systems and simplifying high-bit-rate digital receivers in different applications. From the point of view of packaging, detectors with vertical-illumination configuration can be easily handled by pick-and-place tools and are a popular choice for making photo-receiver modules. However, vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from inter-constraint between high speed and high responsivity. Here, we report a high responsivity vertical-illumination Si/Ge UTC photodiode based on a silicon-on-insulator substrate. The maximum absorption efficiency of the devices was 2.4 times greater than the silicon substrate owing to constructive interference. The Si/Ge UTC photodiode was successfully fabricated and had a dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25% thinner Ge absorption layer.Comment: 5pages,2figure

Oxidation Degradation of Rhodamine B in Aqueous by UV

The UV photolysis of persulfate (S2O8 2−) is a novel advanced oxidation technologies (AOTs), which leads to the formation of strong oxidizing radicals, sulfate radicals (SO4 •−). The effect of oxidant S2O8 2− concentration, initial dye concentration, initial pH of solution, and various inorganic anions (Cl−, H2PO4 −, and HCO3 −) were investigated using Rhodamine B (RhB), a kind of xanthene dye, as a model pollutant. With the increase of oxidant S2O8 2−, more SO4 •− produced to attack RhB molecules and result in the increase of RhB degradation. While the improvement was not sustained above a critical value, beyond which degradation rate does not increase. Initial pH of solution had great effect on the RhB degradation rate during UV/S2O8 2− system. SO4 •− is rather stable in acidic solutions, while increasing system pH results in the transformation of SO4 •− to •OH. The effects of three inorganic anions (Cl−, H2PO4 −, and HCO3 −) all had some negative effect on the degradation of RhB. Based on the RhB solution changes of the UV-vis absorption intensity during the UV/S2O8 2− treatment, decolorization of RhB accompanied the destruction of aromatic ring structures of RhB molecules

Texture Evolution and Grain Competition in NiGe Film on Ge(001)

National Natural Science Foundation of China [61176092, 61036003, 60837001]; National Basic Research Program of China [2012CB933503, 2013CB632103]; Ph. D. Programs Foundation of Ministry of Education of China [20110121110025]; Fundamental Research Funds for the Central Universities [2010121056]; Natural Science Foundation of Fujian Province of China [2012J01284]; Opened Fund of the State Key Laboratory on Integrated Optoelectronics [2011KFB004]To understand the agglomeration mechanism of NiGe films grown on Ge(001), texture structures of NiGe films are revealed by X-ray pole figure measurement. Two preferred epitaxial orientations of the NiGe grains are identified to be NiGe(4 (5) over bar4) II Ge(001) NiGe[(1) over bar 01] II Ge[110] and NiGe(130) II Ge(001) NiGe[002] II Ge[110]. The component of the first epitaxial alignment becomes dominating and the latter diminishing with increasing annealing temperature. The NiGe grains of the second epitaxial alignment are unstable and diminishing at high temperature due to the relatively higher interface/surface energy. The competition of grains with various epitaxial orientations has made a significant contribution to film agglomeration. (C) 2013 The Japan Society of Applied Physic

Layout Design and Optimization of RF Spiral Inductors on Silicon Substrate

The effects of key geometrical parameters on the performance of integrated spiral inductors are investigated with the 3D electromagnetic simulator HFSS. While varying geometrical parameters such as the number of turns （N）,the width of the metal traces （W）,the spacing between the traces （S）,and the inner diameter （ID）, changes in the performance of the inductors are analyzed in detail. The reasons for these changes in performance are presented. Simulation results indicate that the performance of an integrated spiral inductor can be improved by optimizing its layout. Some design rules are summarized

DCXRD Investigation of a Ge/Si（001） Island Multilayer Structure

A Ge/Si（001） island multilayer structure is investigated by double crystal X-ray diffraction, transmission electron microscopy,and atomic force microscopy. We fit the satellite peaks in the rocking curve by two Lorentz lineshapes, which originate from the wetting layer region and the island region. Then from the ratio of the thick- nesses of the Si and Ge （GeSi） layers as determined by TEM,tbe Ge compositions of the wetting layer and islands are estimated to be about 0. 51 and 0. 67, respectively,according to the positions of the fitted peaks. This proves to be a relatively simple way to investigate the Ge/Si （001） island multilayer structure