Showing papers in "Physica E-low-dimensional Systems & Nanostructures in 2001"
Journal Article•
TL;DR: In this article, a room-temperature electrical injection and detection of spin currents and observed spin accumulation in an all-metal lateral mesoscopic spin valve, where ferromagnetic electrodes are used to drive a spin-polarized current into crossed copper strips.
Abstract: Finding a means to generate, control and use spin-polarized currents represents an important challenge for spin-based electronics, or `spintronics'. Spin currents and the associated phenomenon of spin accumulation can be realized by driving a current from a ferromagnetic electrode into a non-magnetic metal or semiconductor. This was first demonstrated over 15 years ago in a spin injection experiment on a single crystal aluminium bar at temperatures below 77 K. Recent experiments have demonstrated successful optical detection of spin injection in semiconductors, using either optical injection by circularly polarized light or electrical injection from a magnetic semiconductor. However, it has not been possible to achieve fully electrical spin injection and detection at room temperature. Here we report room-temperature electrical injection and detection of spin currents and observe spin accumulation in an all-metal lateral mesoscopic spin valve, where ferromagnetic electrodes are used to drive a spin-polarized current into crossed copper strips. We anticipate that larger signals should be obtainable by optimizing the choice of materials and device geometry.
831 citations
TL;DR: In this article, a 3D transition metal atom doped ZnO was investigated by ab initio electronic structure calculations based on the local density approximation, and the results showed that the ferromagnetism was induced by hole doping in the Mn atom.
Abstract: Ferromagnetism in a 3d transition metal atom doped ZnO was investigated by ab initio electronic structure calculations based on the local density approximation. It was shown that the anti-ferromagnetic state was stable in Mn atom doped ZnO and the ferromagnetic state was stable in the other transition metal, i.e., V, Cr, Fe, Co or Ni, doped ZnO, if no additional carrier dopant was introduced. Carrier induced ferromagnetism in the Mn atom doped ZnO was also investigated. The results showed that the ferromagnetism was induced by hole doping in the Mn atom doped ZnO. The present calculations will provide us with guidelines to produce ferromagnetic magnetic semiconductors and to control their magnetic state.
236 citations
TL;DR: In this article, the effect of carrier density and Ni content on the structure, magnetic and magneto-transport behaviors of Ni-doped ZnO films was investigated.
Abstract: Magnetic semiconductor (MS), Ni doped ZnO film was fabricated by pulsed laser deposition method on sapphire (0 0 0 1) substrates. Ni dissolves until 25 at % into ZnO by low temperature growth technique. Lattice constant c once increases with increasing Ni content and has maximum point at the Ni content of 5 at % , and then it suddenly decreases. In all the Ni content range, the films exhibits n-type conduction. With increasing the Ni content, the carrier density and mobility decrease. ZnO films with the Ni content range from 3 to 25 at % exhibit ferromagnetic behavior at 2 K . At 30 K , the magnetization against applied magnetic field shows superparamagnetic behavior and it maintains at least up to 300 K . To study the effect of carrier density, Al was additionally doped. The effect of carrier density and Ni content on the structure, magnetic and magneto-transport behaviors are described.
208 citations
TL;DR: In this paper, high-oriented amorphous silicon nanowires (a-SiNWs) were grown on Si (1.1 1/1/1) and the length and diameter of oriented SiNWs are almost uniform, which are 1 μm and 25 nm, respectively.
Abstract: Highly oriented amorphous silicon nanowires (a-SiNWs ) were grown on Si (1 1 1). The length and diameter of oriented SiNWs are almost uniform, which are 1 μm and 25 nm , respectively. Different from the well-known vapor–liquid–solid (VLS) for conventional whisker growth, it was found that growth of the a-SiNWs was controlled by a solid–liquid–solid mechanism (SLS). This synthesis method is simple and controllable. It may be useful in large-scale synthesis of various nanowires.
151 citations
TL;DR: In this article, the authors describe how quantum information may be transferred from photon polarization to electron spin in a semiconductor device, which relies on selection rules for optical transitions, such that two superposed photon polarizations excite two superposition spin states.
Abstract: We describe how quantum information may be transferred from photon polarization to electron spin in a semiconductor device. The transfer of quantum information relies on selection rules for optical transitions, such that two superposed photon polarizations excite two superposed spin states. Entanglement of the electron spin state with the spin state of the remaining hole is prevented by using a single, non-degenerate initial valence band. The degeneracy of the valence band is lifted by the combination of strain and a static magnetic field. We give a detailed description of a semiconductor structure that transfers photon polarization to electron spin coherently, and allows electron spins to be stored and to be made available for quantum information processing.
111 citations
TL;DR: In this article, it was shown that InGaAs/GaAs semiconductor quantum boxes (QBs) open revolutionary opportunities for the application of the concepts of cavity quantum electrodynamics in monolithic microcavities.
Abstract: Spontaneous emission (SE) control in the solid state has been extensively studied for about 10 years as a route toward optoelectronic devices with improved properties or novel functionalities. Thanks to their atom-like emission and to their relatively large oscillator strength, InGaAs/GaAs semiconductor quantum boxes (QBs) open revolutionary opportunities for the application of the concepts of cavity quantum electrodynamics in monolithic microcavities. Such emitters experience in particular a very large enhancement of their spontaneous emission rate (Purcell effect) when inserted in high Q /low volume micropillars (×5) or microdisks (×15). This result opens unique opportunities for the development of solid-state photon guns, able to emit single-photon pulses in a deterministic way. QBs in microdisks should also allow in the near future to achieve a strong coupling regime for a single solid-state emitter.
92 citations
TL;DR: In this article, a full-potential linearized augmented plane-wave (LPW) method was used to calculate the band structure of 3D transition-metal-doped GaAs.
Abstract: Electronic band-structure calculations are carried out for the hypothetical zinc-blende phase of 3d transition-metal monoarsenides as well as periodic supercells of 3d transition-metal-doped GaAs by using the full-potential linearized augmented-plane-wave method. The antiferromagnetic state is stable for zinc-blende FeAs, while the ferromagnetic state is stable for zinc-blende VAs, CrAs, and MnAs. It is expected that (Ga,Cr)As becomes ferromagnetic due to the presence of mobile valence-band carriers (holes), since the electronic band-structure in the ferromagnetic state of (Ga,Cr)As is very similar to that of (Ga,Mn)As.
88 citations
TL;DR: In this article, the dielectric properties of nano Si/C/N composite powder and nano SiC powder at high frequencies have been studied at a frequency range of 8.2-12.4 GHz.
Abstract: The dielectric properties of nano Si/C/N composite powder and nano SiC powder at high frequencies have been studied. The nano Si/C/N composite powder and nano SiC powder were synthesized from hexamethyldisilazane ((Me3Si)2NH) (Me:CH3) and SiH4–C2H2, respectively, by a laser-induced gas-phase reaction. The complex permittivities of the nano Si/C/N composite powder and nano SiC powder were measured at a frequency range of 8.2–12.4 GHz. The real part (e′) and imaginary part (e″) of the complex permittivity, and dissipation factor ( tg δ=e″/e′) of nano Si/C/N composite powder are much higher than those of nano SiC powder and bulk SiC, Si3N4, SiO2, and Si, especially the tg δ . The promising features of nano Si/C/N composite powder would be due to more complicated Si, C, and N atomic chemical environment than in a mixture of pure SiC and Si3N4 phase. The charged defects and quasi-free electrons moved in response to the electric field, diffusion or polarization current resulted from the field propagation. Because there exists graphite in the nano Si/C/N composite powder, some charge carries are related to the sp3 dangling bonds (of silicon and carbon) and unsaturated sp2 carbons. The high e″ and tg δ of nano Si/C/N composite powder were due to the dielectric relaxation. The nano Si/C/N composite powder would be a good candidate for electromagnetic interface shielding material.
86 citations
TL;DR: In this article, the longitudinal optical and acoustic phonons in CdS nanocrystals in the strongly confined regime in the polymer matrix Nafion were studied using Raman spectroscopy.
Abstract: Quantum confinement effects on the longitudinal optical and acoustic phonons in CdS nanocrystals in the strongly confined regime in the polymer matrix Nafion are studied using Raman spectroscopy. The LO-phonon modes show size-dependent asymmetric broadening though the broadening and asymmetry are less than those predicted by the phonon confinement models. Two types of confined acoustic modes corresponding to n =1, l =0 and n =1, l =2 spheroidal vibrations are observed. Softening of the spheroidal modes is observed in the strongly confined regime.
76 citations
TL;DR: It is asserted that self assembly, an important element of future nanotechnology, will likely utilize lithography in so-called “templated self-assembly”, and low-cost, flexible alternatives are discussed.
Abstract: Because many applications of lithography cannot use the optical projection tools developed for the semiconductor industry, either because of high cost or inflexibility, low-cost, flexible alternatives are essential to research and future industries. A subset of these low-cost alternatives is discussed: intimate-contact lithography, interference lithography, and spatial-phase-locked e-beam lithography. It is asserted that self assembly, an important element of future nanotechnology, will likely utilize lithography in so-called “templated self-assembly”.
73 citations
TL;DR: In this article, the anomalous 0.5 and 0.7 conductance plateaus in quantum point contacts in zero magnetic field are analyzed within a phenomenological model, which involves enhanced spin correlations and thermal depopulation of spin subbands.
Abstract: The anomalous 0.5 and 0.7 conductance plateaus in quantum point contacts in zero magnetic field are analyzed within a phenomenological model. The model utilizes the Landauer–Buttiker formalism and involves enhanced spin correlations and thermal depopulation of spin subbands. In particular we can account for the plateau values 0.5 and 0.7, as well as the unusual temperature and magnetic field dependences of the 0.7 plateau. Finally, the model predicts the possibility of coexisting 0.5 and 0.7 plateaus.
TL;DR: In this article, the carrier-mediated ferromagnetism in tetrahedrally coordinated semiconductors is briefly reviewed, and the experimental results for III-V and II-VI compounds are compared to the theoretical results.
Abstract: The current status of research on the carrier-mediated ferromagnetism in tetrahedrally coordinated semiconductors is briefly reviewed. The experimental results for III–V semiconductors, where Mn atoms introduce both spins and holes, are compared to the case of II–VI compounds, in which the ferromagnetism has been observed for the modulation-doped p-type Cd1−xMnxTe/Cd1−y−zMgyZnzTe:N heterostructures, and more recently, in Zn1−xMnxTe:N epilayers. On the theoretical side, a model is presented, which takes into account: (i) strong spin–orbit and kp couplings in the valence band; (ii) the effect of confinement and strain upon the hole density-of-states and response function, and (iii) the influence of disorder and carrier–carrier interactions, particularly near the metal-to-insulator transition. A comparison between the experimental and theoretical results demonstrates that the model can describe the magnetic circular dichroism, the values of TC observed in the studied systems as well as explain the directions of the easy axis and the magnitudes of the corresponding anisotropy fields as a function of confinement and biaxial strain. Various suggestions concerning design of novel ferromagnetic semiconductor systems are described.
TL;DR: In this paper, a diluted magnetic semiconductor Ge1−xMnxTe of NaCl crystal structure is successfully obtained with the Mn concentration x up to x=096 using ionized-cluster beam technique.
Abstract: IV–VI diluted magnetic semiconductor Ge1−xMnxTe of NaCl crystal structure is successfully obtained with the Mn concentration x up to x=096 using ionized-cluster beam technique The (1 1 1) plane of Ge1−xMnxTe is grown epitaxially parallel to the (1 1 1) plane of BaF2 substrate The lattice constant of Ge1−xMnxTe decreases with the increase of Mn concentration At the Curie temperature (Tc), ferromagnetic phase transition occurs as the result of Runderman–Kittel–Kasuya–Yoshida (RKKY) interaction The highest Tc in this study is 140 K for x=051 Temperature dependence of spontaneous magnetization suggests the existence of multiple exchange interactions The distinct magnetic anisotropy is not observed in the magnetization curves applying the magnetic field parallel and perpendicular to the plane The obtained demagnetizing factor is 052, which was smaller than that of the thin film It can be ascribed to the non-uniform magnetization state
TL;DR: In this paper, the formation of vertically and laterally ordered dot superstructures in self-organized quantum dot superlattices is described, based on the long-range elastic interactions between the strained self-assembled quantum dots, providing a driving force for a spatially correlated dot nucleation.
Abstract: The formation of vertically and laterally ordered dot superstructures in self-organized quantum dot superlattices is described. The ordering is based on the long-range elastic interactions between the strained self-assembled quantum dots, providing a driving force for a spatially correlated dot nucleation. For various materials systems, different types of ordered structures have been observed, ranging from vertically aligned dot superlattices for Si/Ge or III–V semiconductors to a fcc-like ABCABC… stacking in IV–VI materials. It is shown that the elastic anisotropy of the spacer material plays a crucial role in this self-organization process. In particular, for materials with very high elastic anisotropy and growth orientations parallel to an elastically soft direction, layer-to-layer dot correlations inclined to the growth direction can be formed. This is shown to be particularly effective for inducing a lateral ordering of the dots within the growth plane, which can lead to a significant narrowing of the dot size dispersion. These conclusions are also supported by Monte Carlo growth simulations.
TL;DR: In this article, the scattering-matrix product of a weakly absorbing medium is related by a unitary transformation to the time-delay matrix without absorption, and the eigenvalues of SS are distributed according to a generalized Laguerre ensemble.
Abstract: The scattering-matrix product SS † of a weakly absorbing medium is related by a unitary transformation to the time-delay matrix without absorption. It follows from this relationship that the eigenvalues of SS † for a weakly absorbing chaotic cavity are distributed according to a generalized Laguerre ensemble.
TL;DR: In this paper, a binary-decision diagram (BDD) logic architecture is implemented by BDD node devices based on quantum wire transistors and single electron transistors realized by the Schottky inplane gate (IPG) and wrap-gate (WPG) control of III-V hexagonal nanowire networks.
Abstract: Previously quantum device research has been done on discrete device levels and lacks a clear vision for high density integration. This paper proposes a new, simple and realistic approach for quantum large scale integrated circuits (QLSIs) where a binary-decision diagram (BDD) logic architecture is implemented by BDD node devices based on quantum wire transistors (QWTrs) and single electron transistors (SETs) realized by the Schottky in-plane gate (IPG) and wrap-gate (WPG) control of III–V hexagonal nanowire networks. To investigate the feasibility of the proposed approach, BDD devices having QWTrs were formed on GaAs/AlGaAs etched nanowire patterns. They showed expected complimentary quantized conductance switching as required to achieve operation at delay-power products near the quantum limit. The use of embedded InGaAs honeycomb wire networks grown by selective MBE on InP substrates is proposed for constructing circuits operating in quantum regime at room temperature.
Journal Article•
TL;DR: In this article, a binary-decision diagram (BDD) logic architecture is implemented by BDD node devices based on quantum wire transistors and single electron transistors realized by the Schottky inplane gate (IPG) and wrap-gate (WPG) control of III-V hexagonal nanowire networks.
Abstract: Abstract Previously quantum device research has been done on discrete device levels and lacks a clear vision for high density integration. This paper proposes a new, simple and realistic approach for quantum large scale integrated circuits (QLSIs) where a binary-decision diagram (BDD) logic architecture is implemented by BDD node devices based on quantum wire transistors (QWTrs) and single electron transistors (SETs) realized by the Schottky in-plane gate (IPG) and wrap-gate (WPG) control of III–V hexagonal nanowire networks. To investigate the feasibility of the proposed approach, BDD devices having QWTrs were formed on GaAs/AlGaAs etched nanowire patterns. They showed expected complimentary quantized conductance switching as required to achieve operation at delay-power products near the quantum limit. The use of embedded InGaAs honeycomb wire networks grown by selective MBE on InP substrates is proposed for constructing circuits operating in quantum regime at room temperature.
TL;DR: The formation of selfassembling quantum dots for the different strained material systems Ge/Si, InAs/GaAs and InP/GaInP in molecular beam epitaxy is discussed in this article.
Abstract: The formation of self-assembling quantum dots for the different strained material systems Ge/Si, InAs/GaAs and InP/GaInP in molecular beam epitaxy is discussed. Intense 1.55 and 1.3μm room temperature photoluminescence is achieved for stacked Ge dots in Si and single InAs dot layers in GaAs, respectively. Small InP/Ga0.52In0.48P quantum dots emit in the visible red spectrum. Strain-induced vertical alignment, size modification and interdiffusion for stacked dot layers are studied. A blue shift of the ground state transition energy is observed for relatively large size stacked Ge and InAs dots. This is ascribed to enhanced strain driven intermixing in vertically aligned islands. For extremely small and densely stacked InP and InAs dots the stronger confinement causes a red shift of the ground state emission. InP/Ga0.52In0.48P quantum dot injection lasers with coupled three-fold stacked InP dots are presented. Ground state lasing is observed at room temperature with a maximum output power up to 250 mW. The threshold current density at 300 K is jthr=2.3kA/cm2, and an external quantum efficiency of ηext=8.5% is measured for a 2 mm long laser cavity.
TL;DR: In this paper, a multi-layer core/shell model was proposed to study the size evolution of the plasmon resonance for nanoparticles within the free surface of nanoparticles in mesoporous silica, where the particle surface interaction with ambient air and the porosity at the particle/matrix interface was considered.
Abstract: The optical absorption has been investigated for silver and gold nanoparticles dispersed within the pores of monolithic mesoporous silica after annealing at different temperatures It has been shown that with reduction of the particle size, the surface plasmon resonance position blue-shifts first and then red-shifts for silver/silica samples, but only red-shifts for gold/silica samples This size evolution of the resonance is completely different from that previously reported for fully embedded particles Based on the interaction of the particle surface with ambient air and the porosity at the particle/matrix interface, we present a multi-layer core/shell model and assume that the chemical adsorption of gas molecules from the air on the free surface of nanoparticles within the pores is mainly responsible for the observed size evolution of the resonance
TL;DR: In this paper, the authors highlight several issues which are most crucial for the understanding of the metal-insulator transition in two dimensions and discuss some common problems in interpreting experimental results on high-mobility Si MOSFETs.
Abstract: The goal of this paper is to highlight several issues which are most crucial for the understanding of the “metal–insulator transition” in two dimensions. We discuss some common problems in interpreting experimental results on high-mobility Si MOSFETs. We analyze concepts and methods used to determine the critical density of electrons at the metal–insulator transition. In particular, we discuss the origin of the temperature dependence of the resistivity and reasons for this dependence to flatten out at some electron density in the vicinity of the metal–insulator transition. This flattening has recently been proposed to indicate a true quantum phase transition. We suggest an alternative interpretation of this result and demonstrate the consistency of our proposition with the experimental data. One of the main questions, which arise in connection with the transition, is whether or not the metallic state is qualitatively distinct from a conventional disordered Fermi liquid. We analyze the arguments in favor of both affirmative and negative answers to this question and conclude that the experimental results accumulated up-to-date do not provide convincing evidence for the new state of matter characterized by a metallic-like residual conductivity. We also discuss in details the measurement and control of the electron temperature; these issues are crucial for interpreting the low-temperature experimental data.
TL;DR: In this article, the energy spectrum and corresponding wave functions of a flat quantum dot with elliptic symmetry were obtained exactly and a detailed study of the effect of ellipticity on the energy levels and the corresponding wave function was made.
Abstract: The energy spectrum and corresponding wave functions of a flat quantum dot with elliptic symmetry are obtained exactly. A detailed study is made of the effect of ellipticity on the energy levels and the corresponding wave functions. The analytical behavior of the energy levels in certain limiting cases is obtained.
TL;DR: In this paper, the magneto-electroluminescence properties of ferromagnetic/non-magnetic semiconductor pn junction light emitting diodes (LEDs) are presented.
Abstract: Magneto-electroluminescence properties of ferromagnetic/nonmagnetic semiconductor pn junction light emitting diodes (LEDs) are presented. A ferromagnetic p-type (Ga,Mn)As layer is grown on i-(In,Ga)As quantum well (QW)/n-GaAs so that the degree of spin polarization of holes injected from (Ga,Mn)As into GaAs can be probed by analyzing the polarization of light emitted from the LED structures. The EL polarization as a function of magnetic field exhibits clear hysteresis below the ferromagnetic transition temperature of (Ga,Mn)As, which is the evidence that spin-polarized electrical current is injected into nonmagnetic semiconductor.
TL;DR: In this article, a room-temperature single-electron tunnelling through these iron oxide particles has been achieved (to the best of our knowledge) using an STM tip-particle-substrate double junction.
Abstract: Iron oxide nanoparticles have been synthesised by the reduction of FeCl 3 ·6H 2 O and FeCl 2 ·4H 2 O (mass ratio 2:1) in propan-2-ol. The particles were stabilised by the addition of lauric acid and the resultant particles could be readily dispersed in chloroform. Room-temperature single-electron tunnelling through these iron oxide particles has been achieved (to our knowledge) for the first time, using an STM tip–particle–substrate double junction. Characterisation of the particles by XPS and FTIR show that they are Fe 2 O 3 , or possibly Fe 3 O 4 with an outer layer of Fe 2 O 3 , coated with a carboxylic acid monolayer. The particle diameter given by TEM is of the order of 5.0±0.9 nm. From the Coulomb staircase behaviour observed in the I – V curves, we estimate a nanoparticle capacitance of 6.7×10 −19 F which is in agreement with that expected for particles of this size.
TL;DR: In this article, the authors measured the electron spin relaxation time τ s in n -modulation doped GaAs/AlGaAs (1 1 0) multiple quantum wells by pump probe method, which is two orders of magnitude longer than that in (0 0 1) GaAs quantum wells.
Abstract: We measured the electron spin relaxation time τ s in n -modulation doped GaAs/AlGaAs (1 1 0) multiple quantum wells by pump probe method. The value of τ s exceeds 10 ns even at room temperature, which is two orders of magnitude longer than that in (0 0 1) GaAs quantum wells. The τ s dependence on quantized-electron energy, pump beam power and temperature can qualitatively be explained by the reduction of the electron-hole exchange interaction due to screening.
TL;DR: In this article, the s−d exchange interaction between the conducting s electron spins and the d electron spins localized at the magnetic transition metal impurities was investigated to investigate the s-d exchange effect.
Abstract: Epitaxial ZnO thin films co-doped with 3d transition metal (TM) (TM=Cr, Mn, Fe, Co, Ni and Cu) and 1 mol % Al were fabricated as a series of oxide-diluted magnetic semiconductors by pulsed-laser-deposition method. Magnetoresistance (MR) of the films was measured to investigate the s–d exchange interaction between the conducting s electron spins and the d electron spins localized at the magnetic TM impurities. A variety of MR behaviors were observed depending on the different TM impurities. It is deduced that the negative MR behavior in the vicinity of zero field is originated from an electron weak-localization effect. Caused by the s–d exchange interaction, the increase of Thomas–Fermi radius Rs and the decrease of spin-disorder scattering with increasingly aligned spins of the TM ion impurities are responsible respectively for the positive and negative MR in the higher magnetic filed.
TL;DR: In this article, the spectral properties of the scattering matrix associated with generic quantum graphs were studied and an exact combinatorial expression for the spectral form factor of the spectral matrix was derived.
Abstract: We study the statistical properties of the scattering matrix associated with generic quantum graphs. The scattering matrix is the quantum analogue of the classical evolution operator on the graph. For the energy-averaged spectral form factor of the scattering matrix we have recently derived an exact combinatorial expression. It is based on a sum over families of periodic orbits which so far could only be performed in special graphs. Here we present a simple algorithm implementing this summation for any graph. Our results are in excellent agreement with direct numerical simulations for various graphs. Moreover, we extend our previous notion of an ensemble of graphs by considering ensemble averages over random boundary conditions imposed at the vertices. We show numerically that the corresponding form factor follows the predictions of random-matrix theory when the number of vertices is large – even when all bond lengths are degenerate. The corresponding combinatorial sum has a structure similar to the one obtained previously by performing an energy average under the assumption of incommensurate bond lengths.
TL;DR: In this paper, the growth of pseudomorphic single crystal Ni 2 MnGa on (0, 0, 1) GaAs has been investigated and superconducting quantum interference device magnetometry measurements show the films to be ferromagnetic with in-plane magnetization and Curie temperatures of ∼340, ∼320, and ∼290 K.
Abstract: Ferromagnetic Ni 2 MnGa and Ni 2 MnGe have been grown on GaAs(0 0 1) and Ni 2 MnIn on InAs(0 0 1) by molecular beam epitaxy. In situ reflection high energy electron diffraction, ex situ X-ray diffraction and transmission electron microscopy selected area electron diffraction indicate the growth of pseudomorphic single crystal (0 0 1) Ni 2 MnGa on (0 0 1) GaAs. Superconducting quantum interference device magnetometry measurements show the films to be ferromagnetic with in-plane magnetization and Curie temperatures of ∼340, ∼320, and ∼290 K for Ni 2 MnGa, Ni 2 MnGe and Ni 2 MnIn, repectively.
TL;DR: In this article, the authors demonstrated spin injection into a semiconductor by using a II-VI-semiconductor spin aligner on top of a GaAs light-emitting diode.
Abstract: Electrical spin injection (i.e., injection of a spin-polarized current) into semiconductors has been a hot topic in semiconductor physics over the past few years. The reasons are obvious: spin injection would pave the way for a fully new class of electronic devices, in which the electron's spin, rather than its charge, is manipulated for information processing. Such devices could, e.g., combine the advantages of a magnetic hard-disk with semiconductor memory. Also, devices dissipating only minimal amounts of energy could be developed, and – because spin is an intrinsically quantum-mechanical property – spin devices could be used for a solid-state implementation of logical gates in a quantum computer. For many years, however, spin injection, usually approached by depositing ferromagnetic metallic contacts on a semiconductor, has remained elusive. We have now demonstrated spin injection into a semiconductor by using a II–VI-semiconductor spin aligner on top of a GaAs light-emitting diode. Spin injection was detected by determining the degree of circular polarization of the electroluminescence of the diode and was as high as 90%.
TL;DR: In this article, the effect of Mn doping in GaAs was revealed as the formation of new states near the Fermi level, which originate from the Mn aceptor state, and are split from the valence-band maximum of the host GaAs.
Abstract: We have studied the electronic structure of Ga 1− x Mn x As by angle-resolved photoemission spectroscopy. The effect of Mn doping in GaAs was revealed as the formation of new states near the Fermi level, which originate from the Mn aceptor state, and are split from the valence-band maximum of the host GaAs. These states would be responsible for the anomalous transport properties of Ga 1− x Mn x As.
TL;DR: In this paper, hole concentration dependence of ferromagnetic transition temperature, determined from residual magnetization-temperature characteristic measured by DC-SQUID magnetometer has been investigated.
Abstract: Magnetotransport and magnetic properties of p-type GaMnAs layers, in which hole concentrations and Mn concentrations are independently controlled by Sn-donor incorporation, have been studied. Negative magnetoresistance has been enhanced by increasing Sn-incorporation. Hole concentration dependence of ferromagnetic transition temperature, determined from residual magnetization-temperature characteristic measured by DC-SQUID magnetometer has been investigated.