High-performance 980-nm quantum-well lasers using a hybrid material system of an Al-free InGaAs-InGaAsP active region and AlGaAs cladding layers grown by metal-organic chemical vapor deposition

We report on the material growth and fabrication of high-performance 980-nm strained quantum-well lasers employing a hybrid material system consisting of an Al-free InGaAs-InGaAsP active region and AlGaAs cladding layers. The use of AlGaAs cladding instead of InGaP provides potential advantages in flexibility of laser design, simple epitaxial growth, and improvement of surface morphology and laser performance. The as-grown InGaAs-InGaAsP(1.6 eV)-AlGaAs(1.95 eV) lasers achieve a low threshold current density of 150 A/cm(2) (at a cavity length of 1500 mu m), internal quantum efficiency of similar to 95%, and low internal loss of 1.8 cm(-1). Both broad-area and ridge-waveguide laser devices are fabricated. For 100-mu m-wide stripe lasers with a cavity length of 800 Irm, a slope efficiency of 1.05 W/A and a characteristic temperature coefficient (T-0) of 230 K are achieved. The lifetime test demonstrates a reliable performance. The comparison with our fabricated InGaAs-InGaAsP(1.6 eV)-AlGaAs(1.87 eV) lasers and Al-free InGaAs-InGaAsP (1.6 eV)-InGaP lasers are also given and discussed. The selective etching between AlGaAs and InGaAsP is successfully used for the formation of a ridge-waveguide structure. For 4-mu m-wide ridge-waveguide laser devices, a maximum output power of 350 mW is achieved. The fundamental mode output power can be up to 190 mW with a slope efficiency as high as 0.94 W/A.

Improved neutron radiation hardness for Si detectors: Application of low resistivity starting material and or manipulation of N-eff by selective filling of radiation-induced traps at low temperatures

Radiation-induced electrical changes in both space charge region (SCR) of Si detectors and bulk material (BM) have been studied for samples of diodes and resistors made on Si materials with different initial resistivities. The space charge sign inversion fluence (Phi(inv)) has been found to increase linearly with the initial doping concentration (the reciprocal of the resistivity), which gives improved radiation hardness to Si detectors fabricated from low resistivity material. The resistivity of the BM, on the other hand, has been observed to increase with the neutron fluence and approach a saturation value in the order of hundreds k Omega cm at high fluences, independent of the initial resistivity and material type. However, the fluence (Phi(s)), at which the resistivity saturation starts, increases with the initial doping concentrations and the value of Phi(s) is in the same order of that of Phi(inv) for all resistivity samples. Improved radiation hardness can also be achieved by the manipulation of the space charge concentration (N-eff) in SCR, by selective filling and/or freezing at cryogenic temperatures the charge state of radiation-induced traps, to values that will give a much smaller full depletion voltage. Models have been proposed to explain the experimental data.

Measurement and analysis of microwave frequency response of semiconductor optical amplifiers - art. no. 682406

The measurement and analysis of the microwave frequency response of semiconductor optical amplifiers (SOAs) are proposed in this paper. The response is measured using a vector network analyzer. Then with the direct-subtracting method, which is based on the definition of scattering parameters of optoelectronic devices, the responses of both the optical signal source and the photodetector are eliminated, and the response of only the SOA is extracted. Some characteristics of the responses can be observed: the responses are quasi-highpass; the gain increases with the bias current; and the response becomes more gradient while the bias current is increasing. The multisectional model of an SOA is then used to analyze the response theoretically. By deducing from the carrier rate equation of one section under the steady state and the small-signal state, the expression of the frequency response is obtained. Then by iterating the expression, the response of the whole SOA is simulated. The simulated results are in good agreement with the measured on the three main characteristics, which are also explained by the deduced results. This proves the validity of the theoretical analysis.

Electroabsorption modulated semiconductor optical amplifier monolithically integrated with spot-size converters

We have demonstrated an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) monolithically integrated with novel dual-waveguide spot-size converters (SSCs) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device is fabricated by means of selective-area MOVPE growth (SAG), quantum well intermixing (QWI) and asymmetric twin waveguide (ATG) technologies with only three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge stripe (BRS) were incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of both easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB DC and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber. (c) 2005 Elsevier B.V. All rights reserved.

Photovoltaic effect of tin disulfide with nanocrystalline/amorphous blended phases

Tin disulfide (SnS2) nanocrystalline/amorphous blended phases were synthesized by mild chemical reaction. Both X-ray diffraction and transmission electron microscopy measurements demonstrate that the as-synthesized particles presented very small size, with a diameter of only a few nanometers. The photoluminescence (PL) spectrum suggests efficient splitting of photo-generated excitons in poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and SnS2 hybrid films. Organic/inorganic hybrid solar cells comprising MDMO-PPV and SnS2 were prepared, giving photovoltage, photocurrent, fill factor and efficiency values of 0.702 V, 0.549 mA/cm(2), 0.385 and 0.148%, respectively, which suggests that this phase-blended inorganic semiconductor can also serve as a promising solar energy material. (C) 2009 Elsevier Ltd. All rights reserved.

Fe/Cr氧化还原电池的铬负极和Cr(III)氧化过程的研究

氧化还原液流电池是近十几年来发展起来的一种大容量的贮能电池，目前研究比较成熟功率，容量较大的是盐酸体系Fe/Cr氧化还原电池。但是对于该体系的铬负极，仍然存在着氢气的伴随发生和铬盐溶液的时效陈化问题，此外，作为隔膜的离子交换膜也不能满足电池的性能要求。本文用循环伏安法、恒电流法、紫外可见分光光度法、交流阻抗法研究了铬负极的性质和溶液的时效陈化问题；探讨了三价铬离子的电化学还原过程；组装了试验型氯化铵体系的Fe/Cr氧化还原液流电池，测试了电池的性能；为降低隔膜的离子选择性的要求，对Cr(III)/Cr(VI)电对的氧化还原反应进行了探讨。讨论了三价铬离子在银离子存在下氧化成铬酸盐的反应机理。用循环伏安法研究了金、银、铜、石墨等电极材料对Cr(III)/Cr(rIII)电对氧化还原可逆性和析氢速度的影响。金电极能催化Cr(III)/Cr(II)电对的氧化还原反应，在溶液中含有Pb~(2+)离子时，具有较高的氢过电位。银、铜电极在电位扫描过程中不断地进行溶解和沉积，电极性能不稳定，而石墨电极上Cr(III)/Cr(II)电对的可连性较差。因此选择金作工作电极。研究了电解液中加入Pb、In、Tl的作用，结果表明，同时添加Pb-In、Pb-Tl比添加Pb、Tl等单一添加剂更能有效地提高氢过电位。电子探针分析表明，Pb、In、Tl在金基底上是均匀分布的。文献上尚未见到在这一电池体系中应用上述复合添加物的报导。在盐酸溶液中，存在着如下平衡：[Cr(H_2O)_4Cl_2] Cl·2H_2O <-> [Cr(H_2O)_5Cl]Cl_2·H_2O<->[Cr(H_2O)_6]Cl_3利用各级络合物的稳定常数计算了不同浓度的Cr(III)离子溶液中，上述三种络合物的浓度。以循环伏安曲线上Cr(III)的还原峰值电流i_p对Cr(H_2O)_4Cl_2~+和Cr(H_2O)_5Cl~+的浓度和作图，得到通过原点的直线。恒电流法研究发现，电位－时间曲线相继在-550mv·vs·scE和-660mv·vs·scE出现二个电位平阶，其电量比与Cr(H_2O)_4Cl_2~+、Cr(H_2O)_5Cl~2+的浓度比相当。据此认为参加电化学反应的活性离子是Cr(H_2O)_5Cl~(2+)和Cr(H_2O)_4Cl_2~+。利用循环伏安法比较了盐酸、氯化铵、醋酸、醋酸铵作电解液时Cr~(3+)离子的反应活性。盐酸体系中氢气的伴发生极为严重。醋酸、醋酸铵体系析氢电流较小、Cr~(3+)离子的反应活性也不高。相对来说，氯化铵体系对Cr(III)/Cr(II)电对的氧化还原反应有较高的活性，而且氢的析出电流也较小。紫外可见分光光度法对盐酸。氯化铵作电解液时铬络离子稳定性的研究表明，在溶液久置过程中，铬络离子在氯化铵体系中比在盐酸体系中稳定。循环伏安法的研究也符合这一结论。由于氯化铵体系的优点，组装了以氯化铵为电解液的铁铬单体电池。当充、放电电流密度为20mA/cm~2时，库仑效率达99％，瓦时效率在60％以上，电池的开路电压可达1.18V。与以盐酸为电解液的电池相比，具有电池开路电压高、放氢量小库仑效率高等优点。由于溶液的酸度低，也延缓了溶液对电池壳体及其附件的腐蚀。看来，它是一种很有希望的电解液体系。为了降低电池对离子交换膜的离子选择性要求，一种有效的方法是采用全铬电池体系，即正负极活性物质分别为Cr(III)/Cr(VI)和Cr(III)/Cr(II)。本文在Pt、石墨、钛电极上在硫酸溶液中对Cr(III)/Cr(VI)电对的氧化还原过程进行了探讨。循环伏安法表明，Cr(III)的氧化与氧的发生同时进行，加入Pb~(2+), Co~(2+)离子使Cr(III)离子的氧化电位负移。加入Ag~+时，在循环伏安曲线上出现Cr(III)离子的氧化峄。表明Ag~+对Cr(III)的氧化过程有较好的催化作用。在Cr(III)离子浓度0.1m时，峰值电位φ_P与扫描速度的对数logV呈线性关系，2ψ_p/2logv=100mv；峰值电流i_p与扫描速度v成正比。浓度在0.07M以下时，峰电位与扫描速度无关，峰电流与扫描速度平方根成正比，表现为扩散控制的过程。银离子存在下，Pt电极上Cr(III)离子的氧化过程的交流阻抗谱图呈现二个半圆，可以认为电极过程包括中间吸附物的生成。

新银盐光度法测定As(III)、As(II)、一甲基胂酸、二甲基胂酸及其应用

本论文新银盐分光光度法测定As(III)、As(V)、一甲基胂酸二甲基胂酸。包括三部分：（一）文献综述，对分光光度法测定形态砷的文献作了较为全面的评述，而且总结了其它仪器分析方法对形态砷的测定，并做了比较。（二）新银盐分光光度法测定As(III)、As(V)、一甲基胂酸和二甲基胂酸。该方法主要是在两种不同的酸条件下，分别两两发生四种形态的胂的氢化物，在两个不同波长下测量吸收，利用二元线性回归分析。得四种形态砷的含量。第一步在0.5M柠檬酸和柠檬酸钠的缓冲溶液中，用KBH_4还原片还原As(III)。二甲基胂酸为氢化物，用硝酸银一聚乙烯醇－乙醇吸收液吸收。在405nm和420nm波长处测量吸收；第二步在50%酒石酸介质中，用2片KBH_4发生As(V)、一甲基胂酸的氢化物，同上吸收，测量，二元线性回归分析结果，即得四种形态砷的含量。（三）新银盐分光光度法测定As(III)、As(V)、一甲基胂酸和二甲基胂酸－在实际样品中的应用。本文运用该种分析方法测定了水样、尿样、植扬样品和生物样品中形态砷的含量，取得了比较好的结果，回收率达95%以上。

稀土(III)及铜(II)、锌(II)有机磷（膦）酸酯配合物的晶体结构和振动光谱研究

本文包括标题配合物的结构和振动光谱两部分，共涉及了M(DMP)_n {n=2.3, M=2a, Nd, Cu. Zn}, Ln(DPP)_3{2n=2a-2u, Y}和Ln(BBP)_3 {Ln=La-Lu. Y}三类三十四个配合物。在结构方面，首次测定了Zn(DMP)_2和Cu(DMP)_2呈现出链状配位高聚结构，而La(DMP)_3, La(DMP)_3则为平面网状配位高聚结构。在Zn(DMP)_2, La(DMP)_3和Nd(DMP)_3中，配体以对称“O－P－O”桥键与金属原子配位，在相邻金属原子间形成双桥键。在Zn(DMP)_2中，每个Zn原子通过“O－P－O”双桥键与另两个Zn原子连接，Zn原子配位数为4，配位多面体为四面体构型；在La(DMP)_3和Nd(DMP)_3中，每个稀土原子通过“O－P－O”双桥键与另外三个稀土原子相连接，稀土原子的配位数为6，配位多面体LnO_6为八面体构型。在Cu(DMP)_3中， 配体以对称和非对称“O－P－O”桥键两种形式存在，其中非对称配位的配体形成为“Cu-O-P_O-Cu"-Cu，在铜原之间形成了一个单氧桥键。每个Cu原子通过双“O－P－O”桥键以及双单氧原子桥键与另外三个Cu原子相连接，Cu原子配位数为5，配位多面体为四角锥构型。在振动光谱方面，得到了上述配合物较为完整的光谱数据，并对主要光谱带进行了归属，如V_(M-O), V_(PO_2), V_(P-O(c)),VC-O, VP-C及σ_PO_2等。在稀土配合物中，稀土配位键的伸缩振动V_(vn-o)位于250cm~(-1)附近。V_(Cu)和V_(Zn-o)，在Cu(DMP)_2和Zn(DMP)_2中，分别为(412cm~(-1), 370cm~(-1))和(393cm~(-1), 386cm~(-1))。V_(as)PO_2和V_sPO_2，在配合物振动光谱中，分别在1130－1249cm~(-1)区和1084－1156cm~(-1)区。在稀土配合物中，VL_(n-o), V_(as)PO_2频率值，随镧系收缩逐渐递增。在Cu(DMP)_2红外谱中，非对称配体和对称配体的V_(as)PO_2和V_sPO_2, 分别为(1249cm~(-1)，1156cm~(-1))及(1177cm~(-1)，1090cm~(-1))，其劈裂值△V(V_(as)PO_2-V_sPO_2)为93cm~(-1)和87cm~(-1)。通过对配合物的常温和低温红外光谱的比较，确认了La(DMP)3和Nd(DMP)_3的176cm~(-1)、Ln(DPP)_3和Ln(BBP)_3的150cm~(-1)附近吸收为晶格振动。Ln(DPP)_3、Ln(BBP_3)的光谱性质与Ln(DMP)_3相似，我们认为它们之间具有相同的骨架结构－平面网状配位高聚结构。

Threshold behavior in backgating in GaAs metal-semiconductor field-effect transistors: Induced by limitation of channel-substrate junction to leakage current

An analytical model is proposed to understand backgating in GaAs metal-semiconductor field-effect transistors (MESFETs), in which the effect of channel-substrate (CS) junction is included. We have found that the limitation of CS junction to leakage current will cause backgate voltage to apply directly to CS junction and result in a threshold behavior in backgating effect. A new and valuable expression for the threshold voltage has been obtained. The corresponding threshold electric field is estimated to be in the range of 1000-4000 V/cm and for the first time is in good agreement with reported experimental data. More, the eliminated backgating effect in MESFETs that are fabricated on the GaAs epitaxial layer grown at low temperature is well explained by our theory. (C) 1997 American Institute of Physics.

Analysis of the optical confinement factor in semiconductor lasers

We derive formulas for the optical confinement factor Gamma from Maxwell's equations for TE and TM modes in the slab waveguide. The numerical results show that the formulas yield correct mode gain for the modes propagating in the waveguide. We also compare the formulas with the standard definition of Gamma as the ratio of power flow in the active region to the total power flow. The results show that the standard definition will underestimate the difference of optical confinement factors between TE and TM modes, and will underestimate the difference of material gains necessary for polarization insensitive semiconductor laser amplifiers. It is important to use correct optical confinement factors for designing polarization insensitive semiconductor laser amplifiers. For vertical cavity surface-emitting lasers, the numerical results show that Gamma can be defined as the proportion of the product of the refractive index and the squared electric field in the active region. (C) 1996 American Institute of physics.

A novel polarization-insensitive semiconductor optical amplifier structure with large 3dB bandwidth

A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure. which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm. 65nm has been obtained in die experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed, The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.

Design and fabrication of polarization-insensitive 1550 mm semiconductor optical amplifiers

Polarization-insensitive semiconductor optical amplifiers (SOA's) with tensile-strained multi-quantum-wells as actice regions are designed and fabricated. The 6x6 Luttinger-Kohn model and Bir-Pikus Hamiltonian are employed to calculate the valence subband structures of strained quantum wells, and then a Lorentzian line-shape function is combined to calculate the material gain spectra for TE and TM modes. The device structure for polarization insensitive SOA is designed based on the materialde gain spectra of TE and TM modes and the gain factors for multilayer slab waveguide. Based on the designed structure parameters, we grow the SOA wafer by MOCVD and get nearly magnitude of output power for TE and TM modes from the broad-area semiconductor lasers fabricated from the wafer.

High power continuous-wave operation of self-organized In(Ga)As/GaAs quantum dot lasers

Quantum dot (QD) lasers are expected to have superior properties over conventional quantum well lasers due to a delta-function like density of states resulting from three dimensional quantum confinements. QD lasers can only be realized till significant improvements in uniformity of QDs with free of defects and increasing QD density as well in recent years. In this paper, we first briefly give a review on the techniques for preparing QDs, and emphasis on strain induced self-organized quantum dot growth. Secondly, self-organized In(Ga)As/GaAs, InAlAs/GaAlAs and InAs/InAlAs Qds grown on both GaAs and InP substrates with different orientations by using MBE and the Stranski-Krastanow (SK) growth mode at our labs are presented. Under optimizing the growth conditions such as growth temperature, V/III ratio, the amount of InAs, InxGa1-xAs, InxAl1-xAs coverage, the composition x etc., controlling the thickness of the strained layers, for example, just slightly larger than the critical thickness and choosing the substrate orientation or patterned substrates as well, the sheet density of ODs can reach as high as 10(11) cm(-2), and the dot size distribution is controlled to be less than 10% (see Fig. 1). Those are very important to obtain the lower threshold current density (J(th)) of the QD Laser. How to improve the dot lateral ordering and the dot vertical alignment for realizing lasing from the ground states of the QDs and further reducing the Jth Of the QD lasers are also described in detail. Thirdly based on the optimization of the band engineering design for QD laser and the structure geometry and growth conditions of QDs, a 1W continuous-wave (cw) laser operation of a single composite sheet or vertically coupled In(Ga)As quantum dots in a GaAs matrix (see Fig. 2) and a larger than 10W semiconductor laser module consisted nineteen QD laser diodes are demonstrated. The lifetime of the QD laser with an emitting wavelength around 960nm and 0.613W cw operation at room temperature is over than 3000 hrs, at this point the output power was only reduced to 0.83db. This is the best result as we know at moment. Finally the future trends and perspectives of the QD laser are also discussed.

Design and fabrication of GaAs OMIST photodetector

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of A1As layer that is grown by MBE form the Ultra-Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage V-s, sufficient incident light can switch OMIST from high impedance low current"off"state to low impedance high current "on"state. The absorbing material of OMIST is GaAs, so if the wavelength of incident light within 600 similar to 850nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.

Applications of dielectric thin film by electron cyclotron resonance plasma chemical vapor deposition for semiconductor photoelectronic devices

The paper reports a method of depositing SiO2, SiNx, a:Si, Si3N4 and SiOxNy dielectric thin films by electron cyclotron resonance plasma chemical vapor deposition (ECR CVD) on InP, InGaAs and other compound semiconductor optoelectronic devices,and give a technology of depositing dielectric thin films and optical coatings by ECR CVD on Laser's Bars. The experiment results show the dielectric thin films and optical coatings are stable at thermomechanical property,optical properties and the other properties. In addition, the dielectric thin film deposition that there is low leakage current is reported for using as diffusion and ion implatation masks in the paper. In the finally, the dielectric film refractive index can be accurately controlled by the N-2/O-2/Ar gas flow rate.