半导体硅的Seebeck系数和电阻率测量

本文介绍了半导体硅的Seebeck系数和电阻率的测量，与Hall系数和电阻率测量实验相对应，从另一个方面了解半导体导电性能的一些特征．由Seebeck系数的正负号确定载流子的类型是P型还是N型．半导体内有两种导电机制：杂质导电和本征导电．在杂质导电区，可以确定晶格散射因子；在本征导电区，可以确定硅的禁带宽度．     

高压对InSb、InAs电学性质的影响

一、引言 有关压力影响半导体材科Ge的电导率及霍尔效应的许多研究工作指明,Ge的禁带宽度是随压力的增加而增大的。在电子导电的Ge中,截流子迁移率随压力增高而下降;而在空穴导电的Ge中,随着压力的增高,空穴的迁移率将增大;当材料处于混合导电的情况下(例如温度升高时),视压力与温度的不同,总的导电的特征可以是电子型的,也可以是空穴型的。在本征导电的情况下,和空穴电子迁移率之差相关连的霍尔     

半导体物理基础

一百多年以前,人们就把周围的材料按照导电能力的大小分为导体(金属)、半导体、绝缘体三类.金属的室温电阻率一般在10～(-4)到10～(-6)欧姆-匣米;绝缘体的电阻率通常大于10～(10)欧姆-厘米;而半导体的电阻率则介于金属和绝缘体之间,在10～(-4)到10～(10)欧姆-匣米的宽广范围之内,并且,其电导率随温度升高能指数式地增大.但是,实际上使半导体成为物质中的一个特殊类别、井在电子技术上得到广泛应用的主要特点是:温度、光照、强电场等多种因素的作用,能大大改变半导体的导电性能,并且用掺人微量杂质的方法,可以显著地改变和控制半导体的电导率…     

柔性透明导电薄膜(ITO)简介

柔性透明导电薄膜（ＩＴＯ）是一种新型半导体材料，目前主要依赖进口，但价格昂贵，国内生产厂家较少．深圳市北庆薄膜技术有限公司经多年研制、开发，形成了年生产５０，０００Ｍ透明导电膜（ＩＴＯ），产品质量完全可以替代同类进口产品．北庆公司所生产的导电膜具有重量轻、体薄、导电性能好、透过率高、耐冲击、可弯曲、可任意冲裁加工等优点，该产品可以用作光电子器件的透明电极、电磁静电屏蔽的透明视窗、观察窗以及防霜加热膜，还可以用在特殊要求的透明器件上作防静电包装，在某些方面它可以取代导电玻璃，并且可以开拓许多导电玻…     

具有特殊电磁性能的有机物貭

大家知道,物体按其导电性能的不同,可以分成导体、絕緣休、半导体。按其磁性的不同則可分为鉄磁体、逆磁体、順磁体。对于多数的有机物质來讲,它們都是不导电的絕緣体和逆磁体、少部分的有机物质的电磁性能則与此相反,它們具有明显的半导体性能和一定的順磁性。对这部分有机物质的半导体性能的研究,早在本世紀初就已开始。但比較大量、系統、深     

导电高聚物的研究进展与展望

导电高聚物是由含一价对阴离子的具有非定域的 －电子共轭体系的高聚物组成，它可以通过化学或电化学掺杂的方法使其电导率在绝缘体、半导体和导体范围内变化．该研究领域虽然只有短暂的十余年历史，但是无论在材料的合成、结构的表征、导电机理、结构与性能的关系以及它在技术上的应用探索等方面都取得了重大的进展，展现了广阔的前景． 本文就导电高聚物的基本性质、研究进展和它在技术上的应用前景等进行综合的讨论和评价．     

半导体玻璃微通道板的研制

介绍了半导体玻璃微通道板的主要性能，并与传统铅硅酸盐玻璃的相关性能进行了比较。阐述了半导体玻璃的研制工艺，研究了利用半导体玻璃材料制备微通道板的工艺途径，开发了靠玻璃本身体电导性质而无需氢还原工艺的微通道板，即半导体玻璃微通道板。研制出孔径为20μm、外径为12mm的半导体玻璃微通道板，实验利用紫外光电法测试了微通道板的增益、闪烁噪声和成像性能。结果表明新型微通道板具有明显的电子增益和低的闪烁噪声，并且通道表面稳定；利用磷硅酸盐玻璃材料可以实现体导电微通道板的制备。     

半导体陶瓷温度传感器原理及其应用

半导体陶瓷是近二十多年才发展起来的一类新型电子陶瓷，它具有许多其他材料所不及的优点． 利用半导体陶瓷优良的半导电性可以制作许多性能良好的传感器．本文着重介绍了ＢａＴｉＯ３系和 　　　　　　　　系ＰＴＣ 热敏电阻器及过渡金属氧化物系ＮＴＣ 热敏电阻器的主要特性参数，导电机理 和在工农业及家用电器中的应用实例．     

柔性透明导电薄膜(ITO)简介

柔性透明导电薄膜 (ITO)是一种新型半导体材料 ,目前主要依赖进口 ,但价格昴贵 ,国内生产厂家较少。深圳市北庆薄膜技术有限公司经多年研制、开发 ,形成了年生产 5 0 ,0 0 0 M透明导电膜(ITO) ,产品质量完全可以替代同类进口产品。北庆公司所生产的导电膜具有重量轻、体薄、导电性能好、透过率高、耐冲击、可弯曲、可任意冲裁加工等优点 ,该产品可以用作光电子器件的透明电极、电磁静电屏蔽的透明视窗、观察窗以及防霜加热膜 ,还可以用在特殊要求的透明器件上作防静电包装 ,在某些方面它可以取代导电玻璃 ,并且可以开拓许多导电玻璃所不…     

半导体材料的区域提纯及区域匀平法

半导体材料是制造半导体器件的先行,也是开展对半导体的科学研究所必不可少的。制备高纯度的結构完整的半导体材料在半导体学的发展史上起了特別重要的意义。我們知道,极微量的杂貭和缺陷对半导体材料导电性能有决定性的作用,它可以使半导体材料具有适合一定器件的要求的性质,也可使半导体变为毫无用处的废物。半导体材料要求的純度是极高的,对制备晶体管用的锗、硅材料来說,通常要在8个9(純度为     

Magnetic semiconductors

As far as the electrical conductivity is concerned, solids are usually classified as metals, semiconductors, or insulators. In metals the concentration of the charge carriers responsible for the electrical conductivity is large, whereas in semiconductors and insulators the carrier concentration is much smaller. The distinction between semiconductors and insulators is based on a difference in the nature of the conductivity. For semiconductors the charge carriers (electrons or holes) occupy the states of energy bands; these states are not Iocalized on particular atoms, but spread throughout the entire crystal. In such a situation the mobility of the carriers can be quite high and would, in fact, be infinite in a rigid periodic lattice; in this model the thermal motion of the atoms induces a scattering of the carriers and thus limits the conductivity to finite values. The classical examples of semiconductors are the elements Si and Ge and compounds such as GaAs, InSb, CdTe, ZnS, etc.     

Ab initio calculation of the intrinsic spin Hall effect in semiconductors

Relativistic band theoretical calculations reveal that intrinsic spin Hall conductivity in hole-doped archetypical semiconductors Ge, GaAs, and AlAs is large [approximately 100(planck/e)(Omega cm)(-1)], showing the possibility of a spin Hall effect beyond the four-band Luttinger Hamiltonian. The calculated orbital-angular-momentum (orbital) Hall conductivity is one order of magnitude smaller, indicating no cancellation between the spin and orbital Hall effects in bulk semiconductors. Furthermore, it is found that the spin Hall effect can be strongly manipulated by strains, and that the ac spin Hall conductivity is large in pure as well as doped semiconductors.     

Transport properties of electrons in energy band tails

Transport properties of electrons in energy band tails of disordered semiconductors are studied experimentally using a material system in which (i) the width and shape of the band-tail are approximately known and (ii) the Fermi energy is controllable. The material is heavily-doped, closely-compensated, crystalline n-GaAs whose compensation ratio can be made arbitrarily close to unity by the use of two techniques that are described in detail. This control of the Fermi level through compensation permits the measurement of the transport properties of electrons at various energies in the band-tail.

Using band tails having a width of ～50 meV, measurements have been made of the temperature dependence of the d.c. conductivity and Hall coefficient, the frequency dependence of the a.c. conductivity and the electric field dependence of the d.c. conductivity (the last two at low temperatures).

The evidence demonstrates the progressively greater localization of states deeper in the tails. No sign is found of a sharp mobility edge. There is a number of close similarities to the properties of amorphous semiconductors but some significant differences. The frequency dependence of the a.c. conductivity at low temperatures is essentially identical with that of amorphous semiconductors in accord with the general interpretation that conductivity at low temperatures takes place by electron hopping among localized states near the Fermi energy. The detailed temperature dependence of the d.c. conductivity at low temperatures is log σ=σ ₀ exp [?(T ₀/T)^1/2], thus disagreeing with a theoretical expectation that the exponent for low temperature hopping conduction should be 1/4. At low temperatures, the electric field dependence of the conductivity shows a variation as σ～exp (bF/T) over a considerable range extending down to field strengths close to 1 V/cm. This closely resembles recent observations on amorphous semiconductors but the range of field strengths here is lower by several orders of magnitude.     

Breakdown of metallic conductivity in quasicrystals

In the icosahedral phases i-AlCuFe, i-AlPdMn and i-AlPdRe, the electrical conductivity is in the same range as for doped semiconductors. Strong similarities are observed between the direct and tunneling conductivity for the i-AlPdRe phase and for disordered systems on both sides of the metal–insulator (MI) transition.     

Poole-Frenkel effect in chalcogenide semiconductors with various crystalline structures

The results of investigation of electrical conductivity of a large group of chalcogenide semiconductors having the layered, cubic, and orthorhombic structures in strong electric fields up to 10⁵ V/cm are presented. The revealed increase in electrical conductivity σ in strong electric fields has been explained by the Frenkel thermionic ionization. This has made it possible, along with other parameters (for example, activation energy and trap concentration, charge-carrier mean free path, permittivity), to evaluate the concentration and mobility of charge carriers in semiconductors under study. It has been shown that in strong electric fields in semiconductors, when the thermionic ionization of the traps occurs, their permittivity ?, which is caused by the electron polarization, is determined by the simple formula ? = n ², where n is the refractive index of light.     

Theoretical study on spin-polarized injection of electrical currents into polymer semiconductors

Different from electrons and holes in traditional inorganic semiconductors, the charge carriers in polymer semiconductors are spin polarons and spinless bipolarons. In this paper, a theoretical model is presented to describe the spin-polarized injection of electrical currents from a ferromagnetic contact into a nonmagnetic polymer semiconductor. In this model, a new relation of conductivity to concentration polarization for polymer semiconductors is introduced based on a three-channel model to describe the spin-polarized injection of electrical currents under large electrical current densities. The calculated results of the model reveal the effects of the polaron ratio, the carrier concentration polarization, the interfacial conductance, the bulk conductivity of materials, and the electrical current density, etc. on the spin polarization of electrical currents. As conclusions, the large and matched bulk conductivity of materials, the small spin-dependent interfacial conductance, the thin polymer thickness and the large enough electrical current are critical factors for upgrading the spin polarization of electrical currents in polymer semiconductors. Particularly, when the polaron ratio in polymer semiconductors approaches the concentration polarization of the ferromagnetic contact, a modest concentration polarization is sufficient for achieving a nearly complete spin-polarized injection of electrical currents.     

Photovoltaic effect in unipolar multivalley semiconductors

Abstract

The theory of the nonequilibrium charge carrier transport in unipolar multivalley semiconductors is developed. It is shown that the diffusion of photoexcited nonequilibrium heavy and light electrons in multivalley semiconductors is a correlated process, like the ambipolar diffusion in the case of the electron-hole plasma. The light-induced intervalley transitions, resulting in the imbalance between the subsystems of the light and heavy electrons, give rise to the electromotive force (emf) through the mechanism of the Dember photovoltaic effect. The value of the emf occurring in the ‘metal-semiconductor-metal’ structure is calculated in the linear approximation in terms of the light intensity as a small parameter. It is shown that the emf is determined by the conductivity of heavy and light electron subsystems, as well as by the surface conductivity of the metal-semiconductor interface.     

The electrical conductivity of the strongly defective HgCr 2 Se 4 single crystals

The effect of vacancies on the electrical conductivity in HgCr 2 Se 4 spinels is considered. For this purpose the X-ray studies, the electrical conductivity and the thermopower measurements and the calculation of the vacancy model were used. The above investigations showed that: 1) the single crystals under study are p-type semiconductors, 2) the as grown and vacuum annealed single crystals exhibit Arrhenius plot of the electrical conductivity, 3) the copper doping single crystals reveal the jump of the electrical conductivity near Curie temperature, and 4) the strong defectiveness of the spinel structure makes the magnon excitations impossible below the Curie temperature.     

Thermal conductivity of crystalline chrysotile asbestos

The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg₃Si₂O₅(OH)₄ filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes.     

Phononless hopping in the mobility gap of amorphous semiconductors

Two different theories are analyzed and shown to yield the same result for the phononless contribution to the dc hopping conductivity due to electrons in localized states (with single-electron energies broadened by the electron-phonon interaction) in the mobility gap of amorphous semiconductors. Numerical estimate is then used to show that this mechanism cannot explain experimental data on elemental covalent amorphous semiconductors.