阵列测量方式下的电阻率井壁成象

电阻率成象测井是石油测井中最新一代的测井方法 ,对测井仪器响应的精确模拟 ,可以为此类仪器的优化设计和资料解释提供依据。针对电阻率成象仪激励条件比较复杂的特点 ,同时考虑井下地层固有的非均质性 ,选用有限元方法对仪器产生的位场进行分析 ,并对一些典型的地层模型进行模拟 ,给出其电阻率井壁成象结果 ,直观反映井壁地层特征     

Fast characterization of thin semiconductor layers on high-resistivity substrates

A three-Schottky-barrier FET structure is proposed for the measurement of carrier concentration and drift mobility profiles in thin epitaxial layers on semi-insulating substrates. The advantages of this structure are a simple geometry and a fast and nondestructive technological process. Typical results are also shown for GaAs layers.     

High-frequency conductivity of a thin cylindrical semiconductor wire at arbitrary temperatures

The high-frequency conductivity of a thin straight semiconductor wire with a circular cross section is treated in the context of the classical kinetic theory. The calculation is conducted for an extrinsic semiconductor with a simple band structure at any degree of degeneracy. The relation between the wire radius and the mean free path of charge carriers is taken to be arbitrary. The diffuse mechanism of reflection of charge carriers from the wire boundary is considered.     

Characterisation of charge carrier transport in thin organic semiconductor layers by time-of-flight photocurrent measurements

The paper reviews recent advances in characterisation of charge carrier transport in organic semiconductor layers by time-of-flight photocurrent measurements, with the emphasis on the measurements of the samples with co-planar electrodes. These samples comprised an organic semiconductor layer whose thickness is on the order of a μm or less, and thus mimic the structures of organic thin film transistors. In the review we emphasise the importance of considering spatial variation of electric field in these, essentially two-dimensional structures, in interpretation of photocurrent transients. We review the experimental details of this type of measurements and give examples that demonstrate exceptional sensitivity of the method to minute concentration of electrically active defects in the organic semiconductors as well as the capability of probing charge transport along the channels of different mobility that reside in the same sample.     

The role of local potential minima on charge transport in thin organic semiconductor layers

We have performed a systematic study of dependence of time-resolved photocurrent on the point of charge excitation within the organic semiconductor channel formed by two coplanar metal electrodes. The results confirm that spatial variation of electric field between the electrodes crucially determines transport of photogenerated charge carriers through the organic layer. Time-of-flight measurements of photocurrent demonstrate that the transit time of photogenerated charge carrier packets drifting between the two electrodes decreases with increasing travelling distance. Such counterintuitive result cannot be reconciled with the spatial distribution of electric field between coplanar electrodes, alone. It is also in contrast to expected role of space-charge screening of external electric field. Supported by Monte Carlo simulations of hopping transport in disordered organic semiconductor layer, we submit that the space-charge screens the external electric field and captures slower charge carriers from the photogenerated charge carrier packet. The remaining faster carriers, exhibit velocity distribution with significantly higher mean value and shorter transit time.     

Improved micromorph solar cells by means of mixed‐phase n‐doped silicon oxide layers

A good light trapping scheme is necessary to improve the performance of amorphous/microcrystalline silicon tandem cells. This is generally achieved by using a highly reflective transparent conducting oxide/metal back contact plus an intermediate reflector between the component cells. In this work, the use of doped silicon oxide as alternative n‐layer in micromorph solar cells is proposed as a means to obtain high current values using a simple Ag back contact and no extra reflector between the component cells n‐doped silicon oxide layers with a wide range of optical and electrical properties have been prepared. The influence of different deposition regimes on the material properties has been studied. The main findings are the following: (i) when carbon dioxide is added to the gas mixture, sufficiently high hydrogen dilution is necessary to widen the transition region from highly conductive microcrystalline‐like films to amorphous material characterized by low electrical conductivity; (ii) lower refractive index values are found with lower deposition pressure. Optimal n‐doped silicon oxide layers have been used in both component cells of micromorph devices, adopting a simple Ag back contact. Higher current values for both cells are obtained in comparison with the values obtained using standard n‐doped microcrystalline silicon, whereas similar values of fill factor and open circuit voltage are measured. The current enhancement is particularly evident for the bottom cell, as revealed by the increased spectral response in the red/infrared region. The results prove the high potential of n‐doped silicon oxide as ideal reflector for thin‐film silicon solar cells. Copyright © 2011 John Wiley & Sons, Ltd.     

Constrained notch filtering of nonuniformly spaced samples forenhancement of an arbitrary signal corrupted by a strong FM interference

The proposed method is based on exploring the concept of constrained notch filtering (CNF) as applied to any given arbitrary signal with time varying parameters. First, it is shown that any signal with a constant envelope such as FM may be transformed to a discrete sinusoidal one by applying a nonuniform sampling strategy. Second, a signal buried under a strong FM interference is retrieved by applying CNF in the transformed time domain. The main assumption made is that there exists an auxiliary input which provides information about the instantaneous frequency of the interference     

Fast and nondestructive method of C(V) profiling of thin semiconductor layers on an insulating substrate

A method of C(V) profiling using only two mercury Schottky diodes is described. It allows fast profiles of doping level and conductivity of thin semiconductor layers on insulating substrates to be made, without any damage on the surface. This makes the method useful for wafer mapping in concentration, thickness and conductivity.     

用单一表达式研究由两腔组成的半导体激光器

用射线法导出两段式半导体激光器的端面输出谱。该结果既适用于两段式双稳激光器，也适用于简单的外腔式激光器，于是，我们首次用一个统一的式子对这两种看起来颇为不同的器件的某些特性进行了研究。     

Measuring and calculating the Hall mobility of semiconductor epitaxial layers by a contactless method

A new probe was made from microwave dielectric waveguides. Using this probe, we can measure the magnetoresistance of Al_xGa_1−xAs, Hg_1−xCd_xTe and other epitaxial layers easily. It is a contactless and non-destructive method. During the test, we do not need to specially treat the surface and the shape of the samples. The measuring area is about 4 × 4 mm². This article also presents a method of calculating the mobility of these samples from the magnetoresistance data for different semiconductor materials.     

Cure shrinkage measurement of nonconductive adhesives by means of a thermomechanical analyzer

The conductivity of a nonconductive adhesive (NCA) flip chip interconnect is completely dependent on the direct mechanical contact between the integrated circuit (IC) bump and substrate pad. Cure shrinkage of NCA is critical for the formation of the final contact force in the contacts. However, measurement of the cure shrinkage during cross-linking reaction is fairly difficult. This paper introduces a new, yet simple, approach to measure cure shrinkage of adhesives using a thermo-mechanical analyzer. Isothermal studies of shrinkage change as a function of curing show four distinct regions. First, the thickness of the epoxy decreases due to decreasing viscosity and applied load, followed by a stage where the dimension change is constant as the cross-linking reaction is yet to set in. Once cross-linking begins, the shrinkage reaches a maximum followed by a plateau where the cross-linking reaction has completed. Sharp changes of the slope of cure shrinkage versus degree of cure were observed to coincide with gelation and vitrification. After gelation, a linear relationship between the cure shrinkage and degree of cure was observed to extend until the occurrence of vitrification, which quenches the cross-linking reaction. Applied load in the range of 0.05 N was found to be optimal to minimize measurement errors.     

基于激光半导体技术的光纤点式测温系统

本文研究基于激光半导体技术的光纤点式测温系统。利用半导体材料随温度的变化,其折射率发生变化这一原理,成功地开发出了样机系统,并将该系统应用于高压开关柜内的电缆接头、动、静触点等易发热的接触点处的温度检测。该系统的探头部分采用全光设计,抗电磁干扰,耐高压;主机部分带有RS485接口,采用Modbus工业协议,方便多台主机进行组网。多次试验结果表明,该系统测温精度高,为±1℃;测温范围为-10℃-120℃。     

Growth of n-Si layers by molecular-beam epitaxy on the substrates heavily doped with boron

Epitaxial n-Si layers doped with phosphorus or erbium have been grown by sublimation molecularbeam epitaxy at 500°C on heavily boron-doped p ⁺-type substrates with resistivity ρ = 0.005 Ω cm. Distribution profiles of the B, Er, and O impurity concentrations in the samples were determined by secondary-ion mass spectrometry. A thermal annealing of the substrate in vacuum at 1300°C for 10 min and growth at a very low substrate temperature made it possible to obtain an extremely abrupt profile for doping impurities at the layer-substrate interface. This method for growth of n-p ⁺ junctions considerably improves their electrical and luminescent characteristics.     

基于太赫兹等离激元的半导体表面生化薄膜光谱检测

我们提出了一种利用太赫兹表面等离激元对放置在半导体表面的生化薄膜进行光谱测量的新方法。我们从理论上证明了半导体材料对其上传输的太赫兹表面等离子体波具有较强的表面束缚性,从而提高太赫兹波与半导体表面的生化薄膜之间的相互作用。通过采用太赫兹时域光谱测量系统,我们从实验上分别得到了洋葱表皮的太赫兹表面等离子体波和自由空间太赫兹波透射波谱。实验结果表明,当测量对象是厚度仅为自由空间太赫兹波波长的约百分之一的单层洋葱表皮时,表面等离子体波的透射波谱与自由空间太赫兹波透射波谱相比具有更加多的特征吸收峰。     

基于光子混频连续太赫兹波的厚度检测

为了将光子混频的连续太赫兹波透射成像系统应用于样品厚度检测中,采用该系统获得的相位信息对样品进行了2维厚度测量。利用两个外腔半导体结构的激光器搭建了基于光子混频的连续太赫兹波透射成像系统,并利用X-Y 2维电动平移台放置样品进行点点扫描成像。该系统可同时获得样品的幅度信息和相位信息,在太赫兹波辐射频率0.47THz时,系统信噪比可达68dB。计算得出的厚度值与实际样品的厚度值最大相差0.02mm;另外还分析了平行平面样品干涉效应和样品不同透射强度对厚度测量的影响。结果表明,样品折射率越高,平行平面干涉效应对厚度测量影响越大;样品透射系数越大,测量精度也越高。当样品太赫兹波透射系数大于0.5时,厚度测量精度优于2.0%。     

The electrical properties of phosphorus doped silicon layers obtained by ion implantation through a passivating oxide

The electrical properties of phosphorus doped silicon layers obtained by ion implantation through a passivating oxide are studied. The quality of the fabricated n⁺p diodes is investigated. The influence of the process parameters and of the crystal orientation on the sheet resistance of the n⁺ layers is studied. It is shown that sheet resistances higher than 1 kΩ/□ with a good linearity and a very low temperature coefficient can easily be obtained in a reproducible way.     

The effect of diffusion on space-charge waves in a very thin semiconductor layer†

Convective and absolute instabilities associated with space-charge waves are described in a very thin layer of a semiconductor with negative differential mobility and embedded in an infinite dielectric region. Thermal diffusion of carriers plays an important role in the evaluation of the range of existence of convectively unstable space-charge waves,

Within the range of our approximations the forward growing space-charge waves are shown to exhibit a maximum growth rate for a frequency which is determined in terms of diffusion and parameters of the semiconductor find the surrounding dielectric medium.     

Study of modal structure of a semiconductor laser by measurement of the complex degree of coherence

The evaluation of the amplitude of the lateral transverse modes emitted by a semiconductor laser, by means of near or farfield techniques, generally is not easy. In this paper the behaviour of the optical coherence function provides much more sensitive method of analysis. A simple way of implementing the above analysis is described and the results of an experiment are reported.     

Si/SiGe n-MODFETs on thin SiGe virtual substrates prepared by means of He implantation

Si/SiGe n-type modulation-doped field-effect transistors grown on a very thin strain-relieved Si/sub 0.69/Ge/sub 0.31/ buffer on top of a Si(100) substrate were fabricated and characterized. This novel type of virtual substrate has been created by means of a high dose He ion implantation localized beneath a 95-nm-thick pseudomorphic SiGe layer on Si followed by a strain relaxing annealing step at 850/spl deg/C. The layers were grown by molecular beam epitaxy. Electron mobilities of 1415 cm/sup 2//Vs and 5270 cm/sup 2//Vs were measured at room temperature and 77 K, respectively, at a sheet carrier density of about 3/spl times/10/sup 12//cm/sup 2/. The fabricated transistors with Pt-Schottky gates showed good dc characteristics with a drain current of 330 mA/mm and a transconductance of 200 mS/mm. Cutoff frequencies of f/sub t/=49 GHz and f/sub max/=95 GHz at 100 nm gate length were obtained which are quite close to the figures of merit of a control sample grown on a conventional, thick Si/sub 0.7/Ge/sub 0.3/ buffer.     

Photoelectric characteristics of focal plane arrays based on epitaxial layers of indium antimonide deposited on a heavily doped substrate

Photoelectric characteristics of a 320 × 256-element focal plane array (FPA) with a pitch of 30 μm, whose photosensitive element is formed in the InSb epitaxial layer deposited on a heavily doped substrate, have been investigated. For a relative aperture of 1: 0.94 and an integration time of 1.46 ms, the mean value of the noise-equivalent temperature difference is 10.5 mK, the percentage of defective elements is 0.12%, and the correction time is more than 3 h. The FPA has been compared to similar commercial devices based on bulk InSb.