Tag semiconductors [76 articles]

Abstract

The position of the Fermi level at a metal-semiconductor interface relative to the conduction band has been found to be a constant fraction of the semiconductor band gap for all but 3 of the 14 group IV or III-V semiconductors studied. In all cases, the position was essentially independent of the metal work function. This general result is not inconsistent with the limited theories of surface state energies now available. The three exceptional cases can be understood in terms of a ...

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The random distribution of impurities in a semiconductor host lattice introduces potential fluctuations that allow energy levels within the forbidden energy gap. This statistical effect distorts the unperturbed density of states of the pure semiconductor, and, at high doping concentrations, substantial band tails appear. The changes in the density-of-states function are particularly important in determining the number of free carriers in a heavily doped semiconductor. Together with many-particle interactions, band tailing constitutes one of the most significant heavy-doping effects. Although the ...

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We present an ab initio description of charge transport in organic semiconductors based on a recently developed theory that goes beyond small-polaron and/or narrow-band models. The mobility expression is evaluated with parameters from density functional theory, and application to naphthalene crystals demonstrates substantial progress in the simulated temperature dependence and relative magnitudes for all transport directions. The scattering by phonons is described in a manner that goes beyond the Holstein model for small polarons and, consequently, significantly improves the temperature dependence ...

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A review is presented of the various theoretical methods that have thus far been developed for the study of states introduced by impurities and other point defects in semiconductors. The main body of the paper is prefaced with brief sections on the role of impurities and defects in semiconductors and on the general aspects of experimental techniques, as an appropriate setting for the theoretical discourse. Theoretical methods, including those of the effective-mass type, and a wide range of methods appropriate to ...

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Photoluminescence (PL) and deep level transient spectroscopy (DLTS) measurements were used to study the origin of optical emissions in the 0.8–1.0 eV region of selected oxygen precipitated and dislocated silicon samples. It was shown that the D1 band, present in both types of samples, is the convolution of different sub-bands, narrowly spaced between 0.802 and 0.820 eV. The emission at 0.807 eV, assigned in the literature to dislocations, was found only in samples where dislocations were intentionally generated by plastic deformation ...

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We present results of high field magnetoconductance (MC) measurements on In 2 O 3−x films in the hopping regime. For relatively weak disorder, a purely positive MC is observed. With growing disorder, the MC acquires a negative component that tends to saturate at high fields. The data for the latter case are consistent with the co-existence of two mechanisms for MC; an isotropic, spin-alignment mechanism and an anisotropic, quantum-interference one. ...

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The idea of cooling a solid-state optical material by simply shining a laser beam onto it may seem counterintuitive, but this is rapidly becoming a promising technology for future cryocoolers. Here, we chart the evolution of the science of optical refrigeration in rare-earth-doped solids and semiconductors from its origins through to the present day. ...

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The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond ...

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This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto- and electrooptics, high-excitation effects, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. New or updated ...

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The relativistic nature of the electron motion underlies the intrinsic part of the anomalous Hall effect, believed to dominate in ferromagnetic (Ga,Mn)As. In this paper, we concentrate on the crystal band structure as an important facet to the description of this phenomenon. Using different k.p and tight-binding computational schemes, we capture the strong effect of the bulk inversion asymmetry on the Berry curvature and the anomalous Hall conductivity. At the same time, we find it not to affect other important characteristics of (Ga,Mn)As, namely the Curie temperature and ...

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The use of discrete organic compounds as active materials in transistors is described, beginning with [small alpha]-sexithiophene ([small alpha]-6T) and progressing to other thiophene oligomers and nonthiophene semiconductors. Device operation, molecular design, synthesis, film morphology and transport of holes and electrons are covered. ...

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The electron drift mobilities of the five direct-gap III-V semiconductors GaAs; GaSb; InP; InAs; and InSb are presented as a function of temperature. Polar-mode; deformation-potential acoustic; and piezoelectric scattering are included; as well as nonparabolic conduction bands and the corresponding electron wave functions. The drift mobility follows exactly from the assumed model by a simple iterative technique of solution which retains all the advantages of variational techniques without; however; the need for excessive mathematical detail. Piezoelectric scattering is shown to be ...

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In the mid-1980s, Japanese firms strongly challenged American dominance of the semiconductor industry. A large literature arose to suggest that, in order to survive, American firms needed to adopt the capabilities and strategies of the Japanese. Recently, American firms have indeed surged back to regain a strong position in the industry. This essay attempts to collect some of the lessons for strategy research of that American resurgence. We argue that, although some of the American response did consist in changing or ...

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Undoped, high-quality diamond is, under almost all circumstances, one of the best insulators known. However, diamond covered with chemically bound hydrogen shows a pronounced conductivity when exposed to air. This conductivity arises from positive-charge carriers (holes) and is confined to a narrow near-surface region. Although several explanations have been proposed, none has received wide acceptance, and the mechanism remains controversial. Here, we report the interactions of hydrogen-terminated, macroscopic diamonds and diamond powders with aqueous solutions of controlled pH and oxygen concentration. ...

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Focusing specifically on silicon devices, the Third Edition of Device Electronics for Integrated Circuits takes students in integrated-circuits courses from fundamental physics to detailed device operation. Because the book focuses primarily on silicon devices, each topic can include more depth, and extensive worked examples and practice problems ensure that students understand the details. ...

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Laser-induced ultrafast order-disorder transitions in silicon and gallium arsenide are studied by means of femtosecond time-resolved linear and nonlinear optical spectroscopy. Detailed measurements of the reflectivity and of the reflected second harmonic over a wide range of fluences reveal a complex picture of the phase transformation. We show that during the first 100 fs the changes of the optical constants and of the nonlinear optical susceptibility χ(2) are determined by the various electronic excitation processes and only to a lesser extent ...

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Retaining the comprehensive and in-depth approach that cemented the bestselling first edition's place as a standard reference in the field, the Handbook of Semiconductor Manufacturing Technology, Second Edition features new and updated material that keeps it at the vanguard of today's most dynamic and rapidly growing field. Iconic experts Robert Doering and Yoshio Nishi have again assembled a team of the world's leading specialists in every area of semiconductor manufacturing to provide the most reliable, authoritative, and industry-leading information available. Stay Current with the Latest Technologies In addition to ...

Abstract

Printing is considered an attractive technology for realizing electronic functionality at low cost. Inkjet printing, in particular is very attractive for applications requiring low material consumption and spatially-specific material deposition. We report on inkjet-printed transistors offering performance approaching that of amorphous silicon, fabricated using nanoparticle-based metallization and organic-based semiconductors and dielectrics. The performance of these devices is among the highest reported for fully-printed transistors. We explore the optimization of the various printing parameters to maximize device performance and film properties. We ...

Note (first note only)

Review of all-printed OFET fabrication from Subramanian. Metal nanoparticle inks, printable dielectrics down to 20 nm thickness, printable semiconductors.

Abstract

The semiconductor industry is often cited as a "strategic" industry in part because important learning-by-doing spillovers may justify special industrial policies. Documenting the precise nature of these spillovers is crucial for determining the advisability of such policies and is helpful for understanding the contribution of learning to endogenous growth. Yet existing empirical evidence on learning by doing in semiconductor production is scant and evidence on spillovers is nonexistent. Using quarterly, firm-level data on seven generations of dynamic random access memory (DRAM) ...

Abstract

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In this review, we focus on the field of organic photovoltaic cells based on small molecular weight materials. In particular, we discuss the physical processes that lead to photocurrent generation in organic solar cells, as well as the various architectures employed to optimize device performance. These include the donor-acceptor heterojunction for efficient exciton dissociation, the exciton blocking layer, the mixed or bulk heterojunction, and the stacked or tandem cell. We show how the choice of materials with known energy levels and ...

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The light-induced spectral diffusion and fluorescence intermittency (blinking) of semiconductor nanocrystal quantum dots are investigated theoretically using a diffusion-controlled electron-transfer (DCET) model, where a light-induced one-dimensional diffusion process in energy space is considered. Unlike the conventional electron-transfer reactions with simple exponential kinetics, the model naturally leads to a power-law statistics for the intermittency. We formulate a possible explanation for the spectral broadening and its proportionality to the light energy density, the –3/2 power law for the blinking statistics of the fluorescence ...

Abstract

Two-color quantum interference control in a semiconductor results in a charge current or a modulation of the carrier population depending on the phase shift between an optical wave and its second harmonic. Population control requires certain polarizations for the two colors with respect to the crystal axes. The authors present results of an electrical measurement of quantum interference control of charge carrier population in (111) oriented GaAs. The dependence of the population control signal on power, light polarization, bias, and laser ...

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We demonstrate all-optical quantum interference injection and control of a ballistic pure spin current ( without an accompanying charge current) in GaAs/AlGaAs quantum wells; consisting of spin-up electrons traveling in one direction and spin-down electrons traveling in the opposite direction. This current is generated through quantum interference of one- and two-photon absorption of ∼100  fs phase-locked pulses that have orthogonal linear polarizations. We use a spatially resolved pump-probe technique to measure carrier movement of ∼10  nm. Results agree with recent theoretical predictions. ...

Abstract

We have carried out theoretical and experimental investigations of optical phase controlled-free carrier injection in semiconductors via quantum interference between different absorption pathways connecting the same initial and final states in the valence and conduction bands. The interference schemes are theoretically modeled within a Fermi Golden rule approximation which also allows for a description in terms of the susceptibility formalism of nonlinear optics. Two different types of schemes involving interference between n and m multiphoton absorption events are considered depending on ...

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We demonstrate room temperature coherent generation and control of a directional photocurrent in bulk GaAs via simultaneous one- and two-photon interband absorption processes using phase-related 1 ps or 175 fs pulses at 0.775 and 1.55 μm. Electrical currents generated in low-temperature-grown (LT) and normal bulk GaAs are collected via gold electrodes. Current densities as high as 3 nA/μm 2 in LT-GaAs are measured for injected carrier densities as low as 10 14 cm -3 and for peak irradiances ...

Abstract

We show theoretically that interband transitions in a bulk semiconductor via coherent one- and two-photon absorption leads to the formation of an electrical current whose direction is controlled by the relative phase of the beams. The phenomenon can occur in centrosymmetric and noncentrosymmetric materials; easily measurable currents are predicted for GaAs under realistic experimental conditions. ...

Abstract

We present a full band structure scheme to calculate the electronic contribution to the second order susceptibility coefficient pertinent to optical rectification, 2abc" align="middle"/>(–;,) where 0, within the independent particle approximation for the electron dynamics, and in the dipole limit. This allows us to determine the electronic response of a bulk semiconductor to a femtosecond optical pulse over a range of central frequencies, both below and above the band gap frequency. Particularly interesting is the limit 2abc" align="middle"/>(0;,–). In addition to ...

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We show that ballistic current generation can occur in a semiconductor via quantum interference between absorption pathways for orthogonal polarization components of a single-frequency beam. This effect occurs for a subset of noncentrosymmetric materials, is macroscopically associated with a second-order nonlinear optical susceptibility, and produces current injection linearly proportional to the beam intensity. We demonstrate this in wurtzite CdSe (Eg = 1.75 eV) at 295 K using cw and femtosecond optical sources of wavelength 600–750 nm (2.07–1.66 eV). The intensity and ...

Abstract

Phase- and polarization-dependent optical processes involving pulses with frequencies and 2 can be used to independently control electron and spin density in zinc-blende semiconductors such as GaAs. One such process is quantum interference control (QUIC) where interference between transition amplitudes associated with one- and two-photon absorption alters the carrier/spin generation rate. A second process, which has been acknowledged but not utilized, is cascaded second-harmonic (CASH) generation in which phase-dependent upconversion/downconversion between the two pulses modulates the 2 pulse intensity and/or ...

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We demonstrate coherent generation and control of electrical currents in low-temperature-grown GaAs at 300 K using three phase-related, 150 fs pulses derived from a parametric process. Interference between single photon (0.8 µm) and nondegenerate two photon (1.4 and 1.8 µm) absorption amplitudes generates ballistic electrical currents whose beam polarization dependence is in agreement with a simple Fermi's golden rule calculation. ©1999 American Institute of Physics. ...

Abstract

We report broadband terahertz radiation from ballistic photocurrents generated via quantum interference of one- and two-photon absorption in low-temperature-grown and semi-insulating GaAs at 295 K. For 90 fs, 1550 and 775 nm optical pulses, we obtain phase-controllable near-single cycle 4 THz radiation. Higher frequency THz emission should be achievable with shorter pulses. At a 250 kHz repetition rate and average powers of 10 mW (1550 nm) and 400 µW (775 nm), we measure 3 nW of THz power, limited mainly by ...

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Quantum interference between one- and two-photon absorption pathways allows coherent control of interband transitions in unbiased bulk semiconductors; carrier population; carrier spin polarization; photocurrent injection; and spin-current injection can all be controlled. We extend the theory of these processes to include the electron-hole interaction. Our focus is on photon energies that excite carriers above the band edge; but close enough to it so that transition amplitudes based on low-order expansions in k are applicable; both allowed-allowed and ...

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We demonstrate quantum interference control of injected photocurrents in a semiconductor using the phase stabilized pulse train from a mode-locked Ti:sapphire laser. Measurement of the comb offset frequency via this technique results in a signal-to-noise ratio of 40 dB (10 Hz resolution bandwidth); enabling solid-state detection of carrier-envelope phase shifts of a Ti:sapphire oscillator. ...

Note (first note only)

Put an AC signal across a gap with a slab of photoconducting semiconductor in it. When light shines on the semiconductor, get conduction in that location. Size of conduction region is governed by race between free carriers reaching the surface (to induce electric field) and recombination with carriers of the opposite sign. Results at the surface of the semiconductor in an oscillating electric field.

Abstract

A potential implementation of quantum-computation schemes in semiconductor-based structures is proposed. In particular; an array of quantum dots is shown to be an ideal quantum register for a noiseless information encoding. In addition to the suppression of phase-breaking processes in quantum dots due to the well-known phonon bottleneck; we show that a proper quantum encoding allows one to realize a decoherence-free evolution on a time scale long compared to the femtosecond scale of modern ultrafast laser technology. This result might open ...

Abstract

WISEAR (Wireless Sensor Array) is a Linux based Embeddedx86 TS-5600 SBC (Single Board Computer) specifically configured for use with music, dance and video performance technologies. The device offers a general purpose solution to many sensor and gestural controller problems. Much like the general purpose CPU, which resolved many issues of its predecessor (ie., the special purpose DSP chip), the WISEAR box attempts to move beyond custom made BASIC stamp projects that are often created on a per - performance basis and ...

Abstract

Cellular handsets are rapidly evolving from voice-only products to highly featured designs featuring color displays, games, audio, video, cameras, Bluetooth, GPS, WLAN, highspeed wide-area data services, and other advanced features. This remarkable expansion in capability, in conjunction with ongoing customer demands for sleek, ergonomic, and reasonably priced handsets with good battery life, places considerable pressure on handset component providers to aggressively integrate the handset electronics. System-in-package (SIP) integration and system-on-chip (SOC) integration are two possible approaches. This paper investigates the tradeoffs ...

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Optically measured in-line defect data is used for critical area analysis based yield prediction. Because this data can be noisy, however, data can be filtered using kill ratios established from in-line defect to bitmap correlation by mask layer on arrayed devices. This paper reports results from increased granularity of the kill ratio analysis: in-line defect classifications are considered and individual kill ratios for each classification are calculated and used for yield modeling. Furthermore, performing automatic signature classification on the bitmaps and ...