Effective electron-hole potential in polar semiconductors

Summary An accurate analytic expression for the electron-hole effective potential in polar semiconductors is derived, by use of a preceding self-consistent calculation of the author. Its form relies on the main assumption that the excitonic envelope function can be of the 1s-orbital form and that the ground-state wave function is well described in its phonon part by a coherent-state shape with a phonon displacement function depending on the relative electron-hole distance. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Hall coefficient factor in polar semiconductors

The Hall coefficient factor in polar semiconductors is calculated avoiding any serious approximation in the calculation. Lattice scattering (polar optical, acoustic deformation potential and piezoelectric scattering), combined lattice and ionized impurity scattering, and the effect of a nonparabolic conduction band are considered. Results are given both in the limit of vanishing magnetic field and for arbitrary values of the magnetic field. Furthermore our results are compared with experimental values reported previously.     

Secondary radiation in impurity polar semiconductors

An expression is obtained for the secondary radiation section of polar semiconductors due to radiation trapping of electrons or holes at deep impurity levels with the participation of intermediate quasilocal states. The dependence of the section on the frequency of the exciting monochromatic wave is determined mainly by the nonequilibrium electron distribution function, which is a number of equidistant peaks. The spacing between adjacent peaks equals the frequency of the longitudinal optical (LO) phonon, while the peak width is determined by the dispersion of the LO phonons. The distinction between the radiation and Lorentz line shapes is also associated with the form of the electron distribution function.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 89–93, March, 1982.     

Filtering properties of polar semiconductors

The variation of the dielectric function with frequency has been studied for polar semiconductors. The strong coupling between the surface plasmons and surface optical phonons at the surface of a polar semiconductor leads to the study of its filtering properties. The effect of a dc magnetic field on the filtering properties has also been studied. This study on six polar semiconductors GaSb, InSb, InAs, GaAs, GaP and InP has shown that they behave as a band pass and high pass filter.     

Optic phonon-magnetoplasmon surface oscillations in polar semiconductors

An interface between two polar semiconductors in parallel magnetic field geometry can support at most four types of surface oscillations; the actual number (?4), however, depends on the strength of the magnetic field. The interface effects on these relevant ranges of magnetic field are analysed in detail.     

Relaxation semiconductors: In theory and in practice

Relaxation semiconductors are materials dominated by free carrier transport and defined by the condition that the dielectric relaxation time _D is longer than the free carrier lifetime ₀. Novel transport behavior has been demonstrated, both theoretically and experimentally, to be associated with this regime of semiconductor behavior. This review surveys the history of the field, emphasizes recent experimental and modeling work and summarizes our current understanding of relaxation behavior in crystalline semiconductors.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

Non-equilibrium distribution function in polar direct gap semiconductors

Electron distribution function (EDF) for non-equilibrium configurations in polar direct gap semiconductors is obtained in the temperature range k_BT? ? ω_Lo. The sample is assumed to be free of impurities and crystal defects. Electron-phonon coupling is the main relaxation mechanism. Master equation is solved approximately and analitycal expressions for EDF are obtained. Average electron energy as a function of temperature is discussed.     

Chemical shift of Zeeman masses in polar semiconductors

We discuss the problem of determining effective masses from the Zeeman splitting of 2p-levels in shallow impurities. In polar semiconductors we find the Zeeman mass to depend upon the chemical nature of the impurity (chemical shift), which can usually be described by a central-cell potential. In spite of its short range, it can influence even 2p-levels, if, due to electron-phonon interaction, 1s-one-phonon states are admixed to 2_p-zero-phonon states.     

Monte-carlo calculation of electron transport in polar semiconductors

The momentum distribution of electrons in a polar semiconductor under the influence of an electric field is calculated using a Monte-Carlo method. The scattering is assumed to be exclusively by polar optical phonons. From the distribution function, average momentum and electron temperature are calculated, and compared with similar calculations based on a displaced Maxwellian distribution. Some characteristic features are common for the two models, in particular the phenomenon of electron cooling at low lattice temperatures. However, in contrast to the displaced Maxwellian distribution computations, the Monte-Carlo calculations show that a rapid increase of electron temperature takes place at very low fields, before the onset of cooling. Also the anisotropy of the distribution is entirely different in the two models.A detailed discussion of runaway in connection with Monte-Carlo calculations is given.     

Estimation of hot photoelectron density in polar semiconductors

The fraction of laser excitation energy transferred to the electron gas is calculated for polar semiconductors in case of both monoenergetic and transit electrons involved into heating up the gas. The expressions obtained are used for the estimation of photoelectron density in ZnSe single crystals at 4.2K. The result is in good agreement with the data on photoelectron effective temperature saturation.     

Boson description of many-exciton systems in polar semiconductors

Using a unitary transformation the Hamiltonian of interacting polar excitons is established. Two representative states of the many-exciton systems, the biexciton and the dielectric excitonic liquid are discussed for the materials CdS, CuCl and CuBr.     

Coulomb quantum kinetics in pulse-excited semiconductors

The quantum kinetic equations of the electron and hole densities and the interband polarization are derived for a laser-pulse-excited semiconductor with Coulomb interaction including renormalization effects, excitonic effects and scattering with memory kernels. Numerical solutions of this set of non-Markovian, nonlinear integro-differential equations are obtained for a statically screened Coulomb potential.     

Electron-phonon coupling with donor-acceptor pair recombination in polar semiconductors

An analysis of the electron-LO phonon interaction function S(R) for donor-acceptor pair transitions in polar semiconductors is presented. Contradicting theoretical results (S is a monotonically increasing function of pair separation distance R, ref. 2) with reliable experimental findings (S needs to be a drecreasing function of R, ref. 5) are removed, if the interaction between LO-phonons and the donor (acceptor) is taken into account more rigorously.     

Quantum theory of free carrier absorption in polar semiconductors

A quantum mechanica treatment of the free carrier absorption by electrons in polar semiconductors has been constructed in terms of the Kane model. It takes into account overlap wavefunction factors, intermediate states in other bands, the finite optical phonon energy, and the effects of arbitrary spin orbit splitting on the electron energy and wavefunction. The scattering mechanisms considered include polar optical mode scattering, ionic scattering, piezoelectric and deformation coupled acoustic mode scattering, and electron-electron scattering.The theory, in the appropriate limits, applies to a wide range of photon energies, electron concentrations, and lattice temperatures. It relates the dominant scattering mechanism involved in the various limits to the characteristic behavior of the absorption coefficient as a function of the photon energy. In particular, the dominant scattering mechanism for small carrier concentrations is found to be polar optical mode scattering, which exhibits a λ³ dependence of the absorption coefficient times the index of refraction, (except at the lowest frequencies, where the expected λ² dependence is obtained).Ionic, or impurity, scattering becomes important as the carrier concentration is increased, and the characteristic wavelength dependence of the electron cross section times the index of refraction varies from λ⁴ to λ³, and the absorption coefficient times the index of refraction from λ⁴ to λ², depending on the ratio of the photon energy to the initial electron energies.Comparisons are made with the available data over a wide range of photon energies, temperatures, and electron concentrations, for the III–V compounds InSb, InAs, InP, and GaAs.