Electron-hole Plasmas In Semiconductors Research Articles

Interaction of laser pulse with a quantum electron-hole semiconductor plasma

Interaction of laser pulse with a quantum electron-hole semiconductor plasma

Terahertz plasma oscillations and dissipating solitary pulses in electron–hole semiconductor plasmas

Abstract Linearized modes of oscillation in terahertz range and weakly dissipating electrostatic solitary pulses are studied in semiconductor plasmas in the framework of quantum hydrodynamics. Many-particle effect is expressed in the local density approximation with the help of exchange-correlation potential and the species space charge effect is included through Poisson’s equation. Using reductive perturbation technique, damped Korteweg de-Vries equations is derived with a linear damping term arising due to electron (hole)–phonon collisions. Time evolution of solitary acoustic pulses is presented analytically and numerically. Typical values corresponding to GaAs, GaSb, InP and GaN semiconductors are used for parametric analysis and pulse profile with collision-induced dissipation and quantum effects of statistical pressure, Bohm potential and exchange-correlation potential. The pulses are stable and can withstand perturbations for a considerable time before damping.

Impact of an External Magnetic Field on Solitary Waves in Quantum Electron–Hole Plasmas of Semiconductors

The propagation of solitary acoustic pulses in magnetized quantum electron–hole plasmas of semiconductors has been studied. The effects of an external magnetic field and quantum terms, including the electrons and holes quantum recoil effects, exchange-correlation force, and the degenerate pressure of charge carriers are considered. Starting from quantum hydrodynamic equations, by using the reductive perturbation method, the Zakharov–Kuznetsov equation is derived. The theoretical model is applied to three types of semiconductors, namely GaAs, GaSb, and InP. It is clear that basic features of solitary acoustic waves are modified significantly by plasma parameters, especially number densities of semiconductors and magnetic field strength. The value of the amplitude and width of solitary waves strongly depends on the type of semiconductors and the propagation angle in a magnetized quantum electron-hole semiconductor plasma. Numerical results reveal that the width of the solitons gets reduced significantly with the increase of the magnetic field intensity while there is no effect on the amplitude of solitary waves. The weakest magnetic field that sets the pulse width to zero belongs to GaAs. Finally, the stability of the pulse soliton solution of the Zakharov–Kuznetsov equation has been discussed, analytically and numerically. The instability growth rate depends on plasma parameters and magnetic field intensity. The present paper can be meaningful in studying non-linear phenomena and instability behaviors in magnetized quantum electron–hole plasmas of semiconductors and the particle and energy transport mechanism in plasma-assisted quantum semiconductor nanodevices.

Кулоновские корреляции в электронно-дырочной плазме полупроводников в планарном полупроводниковом гетерослое

The paper considers coulomb correlations in electron-hole plasma of semiconductor heterostructures.As a heterostructure, a material based on a solid solution was chosen.As the potential that simulates the heterolayer, one-dimensional parabolic potential is taken.Unlike the commonly used heterolayer potential in the form of a rectangular well, a one-dimensional parabolic potential is chosen in the article.In the framework of this approximation, the Coulomb interaction of an electron and a hole in an exciton was considered as a perturbation.This choice of potential modeling a heterolayer has the following advantages:firstly, it allows us to abandon numerical calculations, replacing them with analytic studies;secondly, since the oscillatory potential grows indefinitely, the Coulomb interaction between the quasiparticles of the electron-hole plasma is small, in comparison with the heterolayer potential, which allows one to take it into account in the framework of perturbation theory.The wave functions of the electron-hole pair for the ground s-state are obtained and with their help the exciton binding energy is calculated as a function of the thickness of the heterolayer.In the framework of perturbation theory, the wave functions of the electron-hole pair (exciton) are obtained, and the main state of the exciton corresponding to the zero orbital momentum of the pair of quasiparticles (the s state of the exciton) is considered in the article.The calculations are performed for the ground state of the exciton corresponding to the s-state of the orbital motion of the electron and hole and zero vibronic numbers.The vibronic quantum numbers corresponding to the motion of an electron and a hole in a direction perpendicular to the heterolayerare also taken to be zero.Such a limit corresponds to a minimum of the exciton energy, i.e. its state of exciton.With the help of the found wave functions, the probability distribution of detection of the electron and hole at a distance ρ is obtained and analyzed as a function of the dimensionless coordinate ξ.With the help of the obtained wave functions, the binding energy of the ground state of the exciton is calculated as a function of the thickness of the heterolayer.The expressions obtained can be generalized to excitons with nonzero orbital quantum numbers.

Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

Magnetosonic solitons in semiconductor plasmas in the presence of quantum tunneling and exchange correlation effects

Low frequency magnetosonic wave excitations are investigated in semiconductor hole-electron plasmas. The quantum mechanical effects such as Fermi pressure, quantum tunneling, and exchange-correlation of holes and electrons in the presence of the magnetic field are considered. The two fluid quantum magnetohydrodynamic model is used to study magnetosonic wave dynamics, while electric and magnetic fields are coupled via Maxwell equations. The dispersion relation of the magnetosonic wave in electron-hole semiconductor plasma propagating in the perpendicular direction of the magnetic field is obtained, and its dispersion effects are discussed. The Korteweg-de Vries equation (KdV) for magnetosonic solitons is derived by employing the reductive perturbation method. For numerical analysis, the plasma parameters are taken from the semiconductors such as GaAs, GaSb, GaN, and InP already existing in the literature. It is found that the phase velocity of the magnetosonic wave is increased with the inclusion of exchan...

Electrostatic Surface Waves on Semi-Bounded Quantum Electron-Hole Semiconductor Plasmas

The electrostatic surface waves on semi-bounded quantum electron-hole semiconductor plasmas are studied within the framework of the quantum hydrodynamic model, including the electrons and holes quantum recoil effects, quantum statistical pressures of the plasma species, as well as exchange and correlation effects. The dispersion characteristics of surface electrostatic oscillations are investigated by using the typical values of GaAs, GaSb and GaN semiconductors. Numerical results show the existence of one low-frequency branch due to the mass difference between the electrons and holes in addition to one high-frequency branch due to charge-separation effects.

Collective excitations of spherical semiconductor nanoparticles

In this article, we study the dispersion properties of bulk and surface electrostatic oscillations of a spherical quantum electron-hole semiconductor plasma as a simple model of a semiconductor nanoparticle. We derive general dispersion relation for both bulk and surface modes, using quantum hydrodynamic theory (including the electrons and holes quantum recoil effects, quantum statistical pressures of the plasma species, as well as exchange and correlation effects) in conjunction with Poisson’s equation and appropriate boundary conditions. We show that for the arbitrary value of angular quantum number there are only two surface plasmon modes, but two infinite series of bulk modes for that owe their existence to the curvature of the interface. We use the typical values of GaAs semiconductor to compute the bulk and surface mode frequencies for different value of .

Colloquium: Nanoplasmas generated by intense radiation

Solid, liquid, and gaseous states of matter can exist and acquire unique properties when reduced in size into a nanometer domain. This Colloquium explores the approaches to produce plasmas with nanometer dimensions and the arising physical phenomena and properties associated with this extreme, nonequilibrium state of matter. Analysis of the spatial confinement, coupling, ideality, and degeneracy criteria lead to the possibilities to produce transient nanoplasma states near, in, and from solids by using ultrafast photoexcitation. These states arise through the interplay of nonequilibrium, many-body Coulomb interactions, thermal, and nonthermal effects. Examples include photoexcited electron-hole plasmas in semiconductors, transient solid-to-plasma states including warm dense matter, nanoplasmas produced by interaction of nanoclusters and nanoparticles with intense radiation, nanoplasmas in high-energy ion tracks within solids, nanoplasmas in relativistic regime, and others. Physical phenomena arising due to the localization of high-energy densities to microscales and nanoscales and their potential applications are discussed.

Quantum effects on compressional Alfven waves in compensated semiconductors

Amplitude modulation of a compressional Alfven wave in compensated electron-hole semiconductor plasmas is considered in the quantum magnetohydrodynamic regime in this paper. The important ingredients of this study are the inclusion of the particle degeneracy pressure, exchange-correlation potential, and the quantum diffraction effects via the Bohm potential in the momentum balance equations of the charge carriers. A modified nonlinear Schrödinger equation is derived for the evolution of the slowly varying amplitude of the compressional Alfven wave by employing the standard reductive perturbation technique. Typical values of the parameters for GaAs, GaSb, and GaN semiconductors are considered in analyzing the linear and nonlinear dispersions of the compressional Alfven wave. Detailed analysis of the modulation instability in the long-wavelength regime is presented. For typical parameter ranges of the semiconductor plasmas and at the long-wavelength regime, it is found that the wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the effect of the Bohm potential may be neglected in comparison with the effect of the exchange-correlation potential in the linear and nonlinear dispersions of the compressional Alfven wave.

One-dimensional rarefactive solitons in electron-hole semiconductor plasmas

We present a theory for linear and nonlinear excitations in semiconductor quantum plasmas consisting of electrons and holes. The system is governed by two coupled nonlinear Schrodinger equations for the collective wave functions of the electrons and holes and Poisson's equation for the electrostatic potential. This gives a closed system including the effects of charge separation between the electrons and holes, quantum tunneling, quantum statistics, and exchange correlation due to electron spin. Three typical semiconductors, GaAs, GaSb, and GaN, are studied. For small-amplitude excitations, the dispersion relation reveals the existence of one high-frequency branch due to charge-separation effects and one low-frequency branch due to the balance between pressure and inertia of the electrons and holes. For the fully nonlinear excitations, the profiles of quasistationary soliton solutions are obtained numerically and show depleted electron and hole densities correlated with a localized potential. The simulation results show that the rarefactive solitons are stable and can withstand perturbations and turbulence for a considerable time.

Electromagnetic surface modes in a magnetized quantum electron-hole plasma

The propagation of surface electromagnetic waves along a uniform magnetic field is studied in a quantum electron-hole semiconductor plasma. A forward propagating mode is found by including the effect of quantum tunneling. In the classical limit (ħ→0), one of the low-frequency modes found is similar to an experimentally observed one in n-type InSb at room temperature. The surface modes are shown to be significantly modified in the case of high-conductivity semiconductor plasmas where electrons and holes may be degenerate. The effects of the external magnetic field and the quantum tunneling on the surface wave modes are discussed.

The role of screening of the electron-phonon interaction in relaxation of photoexcited electron-hole plasma in semiconductors

The role of screening of the interaction of the electron-hole plasma with optical phonons is analytically evaluated by the example of gallium arsenide.

Superfluorescence from dense electron-hole plasmas in high magnetic fields

Cooperative spontaneous recombination (superfluorescence) of electron-hole plasmas in semiconductors has been a challenge to observe due to ultrafast decoherence. We argue that superfluorescence can be achieved in quantum-confined semiconductor systems and present experimental evidence for superfluorescence from high-density photoexcited electronhole plasmas in magnetized quantum wells. At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. Changes in the linewidth, carrier density, and magnetic field scaling of the emission spectra correlate precisely with the onset of random directionality and are consistent with cooperative recombination.

T-matrix approach to equilibium and nonequilibrium carrier-carrier scattering in semiconductors

An analysis of strong-coupling effects in carrier-carrier scattering in electron-hole plasmas in semiconductors is presented. The conventional approach to scattering and dephasing rates is based on the Born approximation (a scattering cross section proportional to the square of the dynamically screened interaction potential), and is strictly valid only in the limit of the weakly coupled quantum plasma. Otherwise, strong correlations are expected to become important in the scattering quantities. Therefore, we perform a thorough analysis of scattering rates in the framework of the statically screened T-matrix (ladder) approximation. We solve the two-particle Schr\odinger equation and provide explicit results for the carrier-carrier scattering rates in equilibrium as well as for optical excitation conditions. Numerical results for GaAs show evidence of significant deviations from the common Born approximation. Finally, dynamic screening effects are included approximately.

Stochastic model of plasma waves for a simple band structure in semiconductors

We consider the application of a stochastic model of two-layer systems to a simple band structure in semiconductors. The telegrapher's equation for the probability density is recovered and the source term is expressed as a function of the electron and hole concentrations. We derive the dispersion relation and we discuss its correction terms with respect to the purely telegrapher's description in fermion systems, for example, a photoexcited electron-hole plasma in semiconductors

Supersonic radiative transport of electron-hole plasma in semiconductors at room temperature studied by laser ultrasonics

A piezoelectric semiconductor CdS 1− x Se x crystal under external electric loading was excited by pulsed nanosecond ultraviolet laser radiation. Acoustic waves were excited via the inverse piezoelectric effect due to the screening of the external electric field by expanding the space distribution of photogenerated electrons and holes. The duration of the interferometrically detected longitudinal acoustic pulses indicated that both the expansion of the screened region in space and the electron-hole plasma expansion are supersonic at the time scale of laser action. The value of 2 × 10 3 cm 2/s obtained for the electron-hole plasma diffusivity leads to the conclusion that the mechanism of this fast carrier transport is photon recycling, i.e. reabsorption of recombination radiation. This conclusion is also supported by the acoustic signals duration independence on magnitude and polarity of the external electric field.

Cooperative coherent phenomena in annihilating electron-positron and electron-hole plasmas in a strong magnetic field

Until now, the phenomenon of collective spontaneous emission (superradiance) was studied, as a rule, for the atomic systems with a discrete energy spectrum. However, it acquires essentially new features in the systems with continuous energy spectra of particles. Two examples of such systems are an electron-position plasma and an electron-hole semiconductor plasma. The review is devoted to the analysis of cooperative, coherent phenomena in these media which demonstrate new remarkable effects of fundamental importance for quantum electrodynamics. The possibility of collective spontaneous annihilation of an electron-positron plasma in a strong magnetic field is predicted. Collective annihilation develops considerably more rapidly than the known incoherent processes of spontaneous annihilation and collisional relaxation and leads to the generation of powerful coherent γ-radiation (annihilation superradiance). The nonrelativistic analog of the electron-positron annihilation is the process of interband recombination of quasiparticles (electrons and holes) in direct-gap bulk semiconductors. We establish the feasibility of collective recombination (recombination superradiance) of a magnetized electron-hole plasma, which develops through interband recombination of free electrons and holes in direct band-gap semiconductors. The limiting parameters of the ultrashort pulses of the recombination superradiance are found. According to our estimates for GaAs, in the magnetic fields of the order of (10 5 – 10 6) G the coherent optical pulses of duration (0.1 – 1) ps and intensity ≳ 100 MW/cm 2 can be generated spontaneously in the samples of typical sizes 3 μm 2 × 30 μm and electron-hole density ≳ 5 × 10 17 cm −3.

The role of the finite collision duration in femtosecond laser studies of semiconductors

The use of femtosecond laser pulses to excite electron-hole plasmas in semiconductors has become a major method of studying fast processes in this system in recent years. Transition times from the central Gamma valley in GaAs to the satellite X and L valleys are comparable to the reciprocal of the frequency of the phonon involved in these transitions, bringing into question the use of standard perturbation theory approaches. The authors present an initial investigation of the role of retardation arising from the finite collision duration required for such a transition to occur, through the use of a path-integral form of the quantum kinetic equation. A secondary self-scattering process and a probability of completed collisions are used to cast this equation in a semi-classical form.

Some properties of vortices in layered superconducting structures

Some properties of vortices in layered superconductors and superconducting structures with the Josephson interaction between S-layers are studied theoretically. The Josephson vortex lattice is formed in the system if the magnetic fieldH e is parallel to the layers. Long-wave oscillations of this lattice have a sound-like spectrum; the velocity of “magnetic sound” propagating across the layers is small and diminishes with increase ofH e . Using an analogy with electron-hole plasma in semiconductors, we investigate also the behaviour of the layered structure in the fieldH e perpendicular to the layers at temperatures close to the Kosterlitz-Thouless transition temperatureT KT. The spatial dependence ofH(r) and the impedance of the system are determined atT>T KT.