Showing papers on "Effective mass (solid-state physics) published in 1996"
TL;DR: In this article, an effective mass for the tunneling electron in the SiO2 layer was extracted from the thickness dependence of the direct tunneling current between an applied voltage of 0 and 2 V, a bias range that has not been previously explored.
Abstract: Electron transport in ultrathin (tox<40 A) Al/SiO2/n−Si structures is dominated by direct tunneling of electrons across the SiO2 barrier. By analyzing the tunneling currents as a function of the SiO2 layer thickness for a comprehensive set of otherwise identical samples, we are able to extract an effective mass for the tunneling electron in the SiO2 layer. Oxide films 16–35 A thick were thermally grown in situ in a dry oxygen ambient. The oxide thicknesses were determined by capacitance–voltage measurements and by spectroscopic ellipsometry. The tunneling effective mass was extracted from the thickness dependence of the direct tunneling current between an applied voltage of 0 and 2 V, a bias range that has not been previously explored. Employing both a parabolic and a nonparabolic assumption of the E−κ relationship in the oxide forbidden gap, we found the SiO2 electron mass to be mP*=0.30±0.02me, and mNP*=0.41±0.01me, respectively, independent of bias. Because this method is based on a large sample set, t...
259 citations
TL;DR: The cubic perovskites can exhibit decisive quantum-fluctuation effects, despite the fact that the lightest constituent is oxygen, and this can occur because these materials have several competing structures with very small structural and energetic differences.
Abstract: Using path-integral Monte Carlo simulations and an ab initio effective Hamiltonian, we study the effects of quantum fluctuations on structural phase transitions in the cubic perovskite compounds SrTiO 3 and BaTiO 3 . We find quantum fluctuations affect ferroelectric ~FE! transitions more strongly than antiferrodistortive ~AFD! ones, even though the effective mass of a single FE local mode is larger. For SrTiO 3 we find that the quantum fluctuations suppress the FE transition completely, and reduce the AFD transition temperature from 130 to 110 K. For BaTiO3 , quantum fluctuations do not affect the order of the transition, but do reduce the transition temperature by 35‐50 K. The implications of the calculations are discussed. Quantum fluctuations typically have a very important effect on the structural and thermodynamic properties of materials consisting of light atoms like hydrogen and helium. For example, quantum effects introduce large corrections to the calculated hydrogen density distribution in the Nb:H system. 1 For materials with heavier atoms, however, the quantum fluctuation can have only a small effect on the distribution of atomic displacements, and thus typically do not have a noticeable effect on the structural and thermodynamic properties of the material. However, exceptions may occur. As we shall see, the cubic perovskites can exhibit decisive quantum-fluctuation effects, despite the fact that the lightest constituent is oxygen. This can occur because these materials have several competing structures with very small structural and energetic differences. 2
237 citations
TL;DR: In this paper, a coherent picture of the band structure near the Γ point and the associated fundamental optical transitions in wurtzite (WZ) GaN, including the electron and hole effective masses and the binding energies of the free excitons associated with different valence bands, has been derived from time-resolved photoluminescence measurements and a theoretical calculation based on the local density approximation.
Abstract: A coherent picture for the band structure near the Γ point and the associated fundamental optical transitions in wurtzite (WZ) GaN, including the electron and hole effective masses and the binding energies of the free excitons associated with different valence bands, has been derived from time‐resolved photoluminescence measurements and a theoretical calculation based on the local density approximation. We also determine the radiative recombination lifetimes of the free excitons and neutral impurity (donor and acceptor) bound excitons in WZ GaN and compare ratios of the radiative lifetimes with calculated values of the ratios obtained with existing theories of free and bound excitons.
176 citations
TL;DR: In this paper, a coupled channel approach based on the Chiral SU(3) Effective Lagrangian was used to study the effective mass and decay width of kaonic modes in baryonic matter.
151 citations
TL;DR: In the framework of effective-mass envelope-function theory, the optical transitions of InAs/GaAs strained coupled quantum dots grown on GaAs (100) oriented substrates are studied and the theoretical results are in good agreement with the available experimental data.
Abstract: In the framework of effective-mass envelope-function theory, the optical transitions of InAs/GaAs strained coupled quantum dots grown on GaAs (100) oriented substrates are studied. At the Gamma point, the electron and hole energy levels, the distribution of electron and hole wave functions along the growth and parallel directions, the optical transition-matrix elements, the exciton states, and absorption spectra are calculated. In calculations, the effects due to the different effective masses of electrons and holes in different materials are included. Our theoretical results are in good agreement with the available experimental data.
144 citations
TL;DR: In this paper, the electronic properties of wide energy gap zinc-blende structure GaN, AlN, and their alloys Ga1−xAlxN were investigated using the empirical pseudopotential method.
Abstract: The electronic properties of wide‐energy gap zinc‐blende structure GaN, AlN, and their alloys Ga1−xAlxN are investigated using the empirical pseudopotential method Electron and hole effective mass parameters, hydrostatic and shear deformation potential constants of the valence band at Γ and those of the conduction band at Γ and X are obtained for GaN and AlN, respectively The energies of Γ, X, L conduction valleys of Ga1−xAlxN alloy versus Al fraction x are also calculated The information will be useful for the design of lattice mismatched heterostructure optoelectronic devices based on these materials in the blue light range application
129 citations
TL;DR: In this article, infrared reflectivity and Hall effect measurements were performed on highly conducting n-type GaN (n≊6×1019 cm−3) bulk crystals grown by the high-pressure high-temperature method.
Abstract: Infrared reflectivity and Hall effect measurements were performed on highly conducting n‐type GaN (n≊6×1019 cm−3) bulk crystals grown by the high‐pressure high‐temperature method. Values of electron‐plasma frequency and free‐electron concentration were determined for each sample of the set of seven crystals. It enabled us to calculate the perpendicular effective mass of electrons in the wurtzite structure of GaN as m*=0.22±0.02 m0. Effects of nonparabolicity and a difference between parallel and perpendicular components of the effective mass are small and do not exceed the experimental error.
129 citations
TL;DR: In this paper, the authors investigated the magnetic breakdown phenomena in the longitudinal magnetoresistance of the quasi-two-dimensional (Q2D) superconductor kappa-(BEDT-TTF)(2)Cu(NCS) in magnetic fields of up to 50 T, well above the characteristic breakdown field.
Abstract: Magnetic breakdown phenomena have been investigated in the longitudinal magnetoresistance of the quasi-two-dimensional (Q2D) superconductor kappa-(BEDT-TTF)(2)Cu(NCS)(2) in magnetic fields of up to 50 T, well above the characteristic breakdown field. The material is of great interest because its relatively simple Fermi surface, consisting of a closed Q2D pocket and an open Q1D band, is almost identical to the initial hypothetical breakdown network proposed by Pippard. Two frequencies are expected to dominate the magnetoresistance oscillations: the a frequency, corresponding to orbits around the closed pocket, and the beta frequency, corresponding to the simplest classical breakdown orbit. However, a beta - alpha frequency is in fact found to be the dominant high-frequency oscillation in the magnetoresistance. Numerical simulations, employing standard theories for calculating the density of states, indicate that a significant presence of the beta - alpha frequency (forbidden in the standard theories) can result simply from the frequency-mixing effects associated with the pinning of the chemical potential in a quasi-two-dimensional system. While this effect is able to account for the previous experimental observation of beta - alpha frequency oscillations of small amplitude in the magnetization, it cannot explain why such a frequency dominates the high-field magnetotransport spectrum. Instead we have extended the numerical simulations to include a quantum interference model adapted for longitudinal magnetoresistance in a quasi-two-dimensional conductor. The modified simulations are then able to account for most of the features of the experimental magnetoresistance data.
84 citations
TL;DR: In this paper, a numerical model of the Landau levels in a quasi-two-dimensional metal was used to simulate the de Haas-van Alphen oscillations observed in high magnetic field measurements.
Abstract: Departures from standard Lifshitz-Kosevich behavior observed in the oscillatory magnetization and magnetoresistance of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) charge-transfer salts in high magnetic fields are investigated using a numerical model of the Landau levels in a quasi-two-dimensional metal. The numerical model enables oscillations in the chemical potential to be treated, as well as the effects of finite temperature, Landau level broadening, and the presence of additional quasi-one-dimensional Fermi surface sheets. The numerical calculations reproduce experimental magnetization data successfully, and allow several phenomena observed in the experiments to be investigated. It is found that pinning of the chemical potential to the Landau levels is responsible for the apparent anomalously low effective masses of the higher harmonics of the de Haas--van Alphen oscillations observed in recent experiments. In addition, the quasi-one-dimensional components of the Fermi surface are found to have a pronounced influence on the wave form of the oscillations in the model, providing a means by which their density of states can be estimated from experimental results. Whilst the magnetization is a thermodynamic function of state, calculations of the behavior of the magnetoresistance are much more model dependent. In this paper, recent theoretical models for the longitudinal magnetoresistance in semiconductor superlattices have been modified for use with the BEDT-TTF salts and are shown to successfully reproduce the form of the experimental data. The strongly peaked structure of the magnetoresistance, which comes about when the chemical potential is situated in or close to the gap between adjacent Landau levels, is found to be responsible for the apparent strong increase of the effective mass which has recently been reported in high field transport measurements. \textcopyright{} 1996 The American Physical Society.
83 citations
TL;DR: In this paper, core and valence level photoemission and electron energy loss (EELs) spectra of MoO2 and WO2 were measured, and it was shown that metal-metal π bonding is important in these compounds.
Abstract: Core and valence level photoemission and electron energy loss (EELs) spectra of MoO2 and WO2 have been measured. Metal–metal bonding in these distorted rutile dioxides splits the metal 4d or 5d conduction band into two components, with a significantly bigger splitting for WO2 than MoO2. The O 2p bandwidth is also found to be bigger for WO2 then MoO2. Plasmon loss peaks below 2 eV show that the effective mass ratios for electrons not involved in σ metal–metal bonding are much greater than unity. The photoemission and EELS data both suggest that metal–metal π bonding is important in these compounds. Comparison between photoemission spectra of WO2 and oxygen-deficient Na0.65WO3 –y suggests that structure evident in the bandgap of the latter compound may be associated with metal–metal bonding allowed by oxygen deficiency.
81 citations
TL;DR: In this article, a software program called CRYSTAL 92 is used to determine the energy band diagrams of In2O3 and In 2O3 doped with Sn, and an empirical relationship is established between the effective mass and free carrier concentration using experimentally observed optical effective mass values.
Abstract: Indium tin oxide (ITO) is a transparent conducting oxide used in a variety of optoelectronic applications. In order to optimize the electrical conductivity of ITO thin films it is necessary to determine this property as a function of optimum electron concentration (e.g., doping of In2O3 with Sn). A new software program called CRYSTAL 92 is used to determine the energy band diagrams of In2O3 and In2O3 doped with Sn. Using the curvature of the conduction bands, the effective mass of the electrons is estimated and an empirical relationship is established between the effective mass and free carrier concentration using experimentally observed optical effective mass values. The importance of the varying electron effective mass in the prediction of the electron mobility, and hence the electrical conductivity, is shown here by comparing the published experimental results with the estimated results. The limiting factor in the electron mobility appears to be either grain boundary scattering or ion impurity scatteri...
TL;DR: In this article, the authors discuss how the technological advances in the semiconductor industry, developed to produce the next generation of micro-chips, have been appropriated by the physics community to test how electron transport processes vary when devices are made smaller than some important physical length scales.
Abstract: Novel submicron devices can now be made from extremely pure crystals containing small numbers of electrons. Using these structures the fundamentals of quantum mechanics can be studied in which fitting theory to experiment only requires the material parameter of effective mass to be known. In this article I will discuss how the technological advances in the semiconductor industry, developed to produce the next generation of micro-chips, have been appropriated by the physics community to test how electron transport processes vary when devices are made smaller than some important physical length scales. Most of the devices I will discuss are made using a two-dimensional electron gas trapped at the interface between GaAs and AlGaAs. This is then laterally patterned to force current transport through a small region. Devices have been demonstrated in which electrons traverse the device without scattering (one-dimensional ballistic conductance), while other devices reveal the nature of single electron transport (zero-dimensional dots). The quantum mechanical wave nature of electron transport is very elegantly shown in devices which mimic optical apparatus such as Fabry - Perot interferometers and lenses. The application of a strong magnetic field to zero-dimensional devices reveal phenomena remarkably similar to the Aharonov - Bohm effect seen in metal loops. This tells us a great deal about how a magnetic field applied to a two-dimensional electron gas forces electrons to travel around the edge of a device. This review was received September 1995
TL;DR: In this article, the effective mass Hamiltonian for wurtzite GaN was presented and solved using block-diagonalized basis functions, such that the band structures near the zone center can be conveniently derived with analytical solutions.
Abstract: We present the effective‐mass Hamiltonian for wurtzite crystals including the strain effects and show analytical solutions for the energy band structures. We found that the Hamiltonian can be block‐diagonalized in our chosen set of basis functions such that the band structures near the zone center can be conveniently derived with analytical solutions. The constant energy surfaces and the valence‐band structures are illustrated graphically. The strain effects on the band structures of the wurtzite GaN are also discussed. This Hamiltonian provides a theoretical foundation for calculating the band structures of the bulk and quantum‐well wurtzite crystals under the framework of the effective mass theory.
TL;DR: In this paper, the spectral line shape of radiative intersubband transitions in a quantum well was investigated, and the electron scattering rate from states of given energy and the mass difference between the two subbands involved were determined.
Abstract: We investigate the spectral line shape of radiative intersubband transitions in a quantum well as determined by two factors: the electron scattering rate from states of given energy and the mass difference between the two subbands involved. The interplay between these factors leads to an essentially non‐Lorentzian form of the spectral line. We develop an analytic theory of the line shape and calculate the dependence of the intersubband optical gain in a quantum well on both the population inversion and the temperature. Under typical conditions, the effect of electron temperature on the gain is similar to that of the lattice temperature, which points to the importance of hot carrier effects in understanding the behavior of intersubband lasers.
TL;DR: In this paper, the authors reported the optical identification of excitonic, donor, and acceptor impurity related transitions at a temperature of 1.4 K and in the presence of magnetic fields up to 7 T support these identifications.
Abstract: Photoluminescence studies as well as reflectance and transmittance measurements were performed on high‐purity epitaxial InAs grown by metal‐organic chemical‐vapor deposition. We report the optical identification of excitonic, donor, and acceptor impurity related transitions at a temperature of 1.4 K. Measurements at higher temperature and in the presence of magnetic fields up to 7 T support these identifications. We find the excitonic band gap at 415.65±0.01 meV according to the minimum in the polariton reflectance feature. The donor–acceptor‐pair and acceptor‐bound exciton transitions for three different acceptors are observed by photoluminescence, and we tentatively associate one of them to a double acceptor formed by a Ga impurity on an As lattice site. A donor‐bound exciton transition is observed with a binding energy of 0.42 meV. The magnetic field dependence yields values of the electron effective mass and g factor of (0.026±0.002)m0 and −15.3±0.2, respectively, in good agreement with values obtained by other techniques. Furthermore, we report a deep luminescence band of unknown origin at ∼375 meV, related to drastic temporal changes in the band‐edge photoluminescence intensity.
TL;DR: In this paper, the semi-classical limit of the dynamics of electrons in a crystal under the influence of an external electric field was studied and two snlall parameters E and h were introduced.
Abstract: We study the semi-classical limit of the dynamics of electrons in a crystal under the influence of an external electric field. Two snlall parameters E and h are introduced. They are respectively re...
TL;DR: In this paper, the 2D hole gas distributions within inversion layers of PMOSFETs have been evaluated by solving the coupled Schrodinger equation and Poisson equation self-consistently based on the effective mass approximation with the light hole and heavy hole subbands taken into account.
Abstract: The 2-D hole gas distributions within inversion layers of PMOSFETs have been evaluated by solving the coupled Schrodinger equation and Poisson equation self-consistently based on the effective mass approximation with the light hole and heavy hole subbands taken into account. The threshold voltage shift resulting from the carrier redistribution due to quantization effects is found to be more significant for PMOSFETs than NMOSFETs on (110) Si substrates. For a certain substrate doping concentration the threshold voltage shift from the classical value due to quantization effects is found to be a combination of substrate band bending and oxide potential differences between the classical and the quantum mechanical models.
TL;DR: It is found that the single-particle-scattering spectrum in InAs can only be observed with the use of a much longer laser pulse width than subpicosecond as a result of electron intervalley scattering and very small electron effective mass.
Abstract: We have used subpicosecond laser pulses to study the generation of nonequilibrium LO phonons in both InP and InAs. These two semiconductors provide a contrast in that the decaying of the Raman signal probes different relaxation mechanisms. In InP, for example, we find that the decay of the Raman signal is dominated by the lifetime of the LO phonons. On the contrary, in InAs, our studies show that the decay of the Raman signal is governed by the time required for electrons to return to the \ensuremath{\Gamma} valley from the L valleys of the conduction bands. In addition, nonequilibrium electron distributions were also studied in InP and InAs. We have found that the single-particle-scattering spectrum in InAs can only be observed with the use of a much longer laser pulse width than subpicosecond as a result of electron intervalley scattering and very small electron effective mass. \textcopyright{} 1996 The American Physical Society.
TL;DR: In this article, the 2D-electron cyclotron mass was determined and discussed in view of nonparabolicity and polaron effects, and the influence of non parabolicity was enhanced by the spatial confinement of electrons and was calculated in the triangular well approximation.
TL;DR: In this article, a survey of tunnelling processes between barrier-separated two-dimensional (2D) systems and systems of different dimensionality is given, where all resonances have their origin in density of states effects, transmission coefficients or the overlap integrals between the initial and final states.
Abstract: In this review a survey of tunnelling processes between barrier-separated two-dimensional (2D) systems and systems of different dimensionality is given. Tunnelling between barrier-separated 2D systems can be studied on very different samples such as triple-barrier structures, double-barrier structures with a two-dimensional emitter, double-barrier structures under hydrostatic pressure, double heterostructures, coupled quantum wells and also coupled 2D electron - hole systems. Pure 2D - 2D tunnelling processes with individual contacts on both 2D systems, however, are only reported on double heterostructures and coupled quantum wells. Using a transfer Hamiltonian formalism, it is shown that all resonances in the tunnelling current have their origin in density of states effects, transmission coefficients or the overlap integrals between the initial and final states. 2D subband energies, background impurity concentrations, the effective mass and also non-parabolicity effects can be determined quantitatively in terms of the transfer Hamiltonian formalism. By nanofabrication, tunnelling processes between 2D systems and states of lower dimensionality (1D, 0D) can also be investigated. Here, the tunnelling processes are mainly influenced by the overlap integral between the initial and final states. The corresponding resonance positions in the tunnelling current strongly depend on the shape of the confining potential and, moreover, the current - voltage characteristics turn out to be the Fourier transform of the 1D (0D) wavefunction of the final state. A brief survey of 1D - 1D and 1D - 0D tunnelling experiments is also given.
TL;DR: In this article, a theoretical description of the optical gain of a quantum-well laser is developed taking into account non-Markovian relaxation and many-body effects, and it is shown that the gain spectra depend strongly on the correlation time of the system which can be determined by the intraband frequency fluctuations.
Abstract: In this article, a theoretical description of the optical gain of a quantum-well laser is developed taking into account non-Markovian relaxation and many-body effects. Single-particle energies are calculated using the multiband effective mass theory, and the valence-band mixing including the spin-orbit (SO) split-off band coupling is considered in the formulation. The Coulomb enhancement and the band-gap renormalization are also considered within the Hartree-Fock approximation. The gain spectra calculated with the Lorentzian line shape function show two anomalous phenomena: unnatural absorption region below the band-gap energy and mismatch of the transparency point in the gain spectra with the Fermi-level separation, the latter suggesting that the carriers and the photons are not in thermal (or quasi-) equilibrium. It is shown that the non-Markovian gain model with many-body effects removes the two anomalies associated with the Lorentzian line shape function. It is also found that the optical gain spectra depend strongly on the correlation time of the system which can be determined by the intraband frequency fluctuations.
TL;DR: In this paper, a new amorphous semiconductor, 2CdO⋅PbOx (band gap: 1.58 eV), was found by rf sputtering of a Cd2PbO4 target in O2-Ar.
Abstract: A new amorphous semiconductor, 2CdO⋅PbOx (band gap: 1.58 eV), was found. Thin films of this material were prepared by rf sputtering of a Cd2PbO4 target in O2–Ar. The dc conductivity of the resulting amorphous thin films was ∼180 S cm−1 at 300 K and remained almost constant down to ∼4 K. The concentration of carrier electrons and the Hall mobility in the as‐deposited state were 1×1020 cm−3 and 9 cm2 V−1 s−1, respectively. When the as‐deposited specimens were heated to 250 °C, which is far below the crystallization (to Cd2PbO4) temperature (460 °C), the conductivity and the carrier concentration at 300 K became approximately twice as high. The thermal O2‐desorption measurements demonstrated that carrier electrons are generated via the formation of oxygen vacancies at the initial stage (<250 °C) of thermal desorption of O2 from the amorphous structure. The effective mass of carrier electrons was estimated as 0.57m0.
TL;DR: In this paper, effective masses derived from the low-field Shubnikov-de Haas oscillations in high mobility GaAs/AlGaAs samples are found to decrease systematically with density.
TL;DR: In this paper, the dependence of the band gaps of Si wires on wire width is calculated within the effective mass theory, taking into account the finiteness of the barrier height of the confinement potential and the boundary conditions for the envelope functions at the interface between the wire and the potential.
Abstract: The dependence of the band gaps of Si wires on wire width is calculated within the effective mass theory, taking into account the finiteness of the barrier height of the confinement potential and the boundary conditions for the envelope functions at the interface between the wire and the confinement potential. Comparing the results with those of the first-principles calculation, we find that, with appropriate boundary conditions, the effective mass theory gives a good description of the electronic states in Si wires down to at least 10 A.
TL;DR: The field dependence of the Hall resistivity has been measured below and above a metamagnetic-like transition (MT) at 50 mK-2 K in a high quality single crystal CeRu2Si2 as discussed by the authors.
Abstract: Field dependence of the Hall resistivity has been measured below and above a metamagnetic-like transition (MT) at 50 mK-2 K in a high quality single crystal CeRu
2Si2. The MT in the Fermi-liquid region is regarded as a continuous modification of resonance quasi-particle band near the Fermi level and no drastic change of carrier density is observed. In contrast, the MT in the incoherent region exhibits no clear change of effective mass or inelastic scattering time. The strong modification of the MT by the coherent effect is discussed.
TL;DR: In this paper, the relativistic mass shift associated with the quiver motion is taken into account in the observation of multiphoton scattering of electrons born in a high-intensity laser focus.
Abstract: Observations of multiphoton scattering of electrons born in a high-intensity laser focus are extended to intensities at which the relativistic mass shift associated with the quiver motion must be taken into account.
TL;DR: In this article, the temperature-dependent thermoelectric power S of insulating and metallic Bi-2212 and Tl-22 12 samples is scaled to universal master curves.
Abstract: The temperature-dependent thermoelectric power S of insulating and metallic Bi-2212 and Tl-2212 samples are scaled to universal master curves. For insulating samples, S passes through a peak at a characteristic temperature , which decreases with increasing carrier concentration. For metallic samples a scaling parameter (= dS/dT at high temperatures) decreases with increasing carrier density. It is argued that is related to the energy needed for activation conduction whereas the change in may be due to increase in with carrier density, where n is the concentration and is the effective mass of the carriers.
TL;DR: A ground-state energy only very slightly lower than the previously reported backflow fixed-node energy is found, reinforcing the conclusion that backflow wave functions are quite accurate and the effective mass is indeed less than bare electron mass for a range of densities around r s51.
Abstract: Energies of the ground state and low-lying excited states of the two-dimensional electron gas have been calculated by a transient-estimate Monte Carlo method. This is an exact fermion quantum Monte Carlo method that systematically improves upon the results of a variational energy without imposing nodal constraints. We focus upon the density r s51, where our previous variational Monte Carlo calculation found qualitative differences in the effective mass from other theoretical approaches. Starting from a wave function with backflow and two-body correlations, the best trial function in our previous variational study, we find a ground-state energy only very slightly lower than the previously reported backflow fixed-node energy, reinforcing the conclusion that backflow wave functions are quite accurate. The effective mass derived from excitation energies does not differ significantly from the variational Monte Carlo results, giving a value of m*/m50.9360.01, so we conclude that the effective mass is indeed less than bare electron mass for a range of densities around r s51.
TL;DR: In this article, the results of electron mobility in strained-Si inversion layers grown on Si1−xGex substrates are reported Drift velocities are calculated by Monte Carlo simulations including electron quantization and Coulomb scattering, in addition to phonon and surface roughness scattering.
Abstract: Results of electron mobility in strained‐Si inversion layers grown on Si1−xGex substrates are reported Drift velocities are calculated by Monte Carlo simulations including electron quantization and Coulomb scattering, in addition to phonon and surface roughness scattering The strain is shown to contribute as well to the enhancement of the Coulomb‐limited mobility due to better screening of the interface centers by the mobile carriers Even in the case of high‐doped substrates, Coulomb scattering does not cancel the mobility enhancement provided by the reduction of both intervalley scattering and conduction effective mass
TL;DR: In this article, the tunnel current through 3.0-6.0 nm thick SiO 2 grown on Si(100) substrates has been compared with the theory of the WKB approximation.
Abstract: The tunnel current through 3.0–6.0 nm thick SiO 2 grown on Si(100) substrates has been compared with the theory of the WKB approximation. By using the measured conduction band barrier height, the electron effective mass, which is only the fitting parameter, is obtained to be (0.34 0.04)m 0 in the Fowler-Nordheim tunneling region and (0.29 0.02)m 0 in the direct tunneling region. It is also shown that the charge-to-breakdown for electron injection from n + poly-Si gates is not significantly deteriorated by decreasing the oxide thickness to 3.3 nm and even dramatically improved for the case of a 3.0 nm thick gate oxide. Quasi-breakdown current observed in ultrathin SiO 2 has been analyzed and a new dielectric degradation model is proposed.