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Title: Dielectric function for a model of laser-excited GaAs

Abstract

We consider a model for the ultrashort pulsed-laser excitation of GaAs in which electrons are excited from the top of the valence band to the bottom of the conduction band. The linear optical response of this excited system in the visible and near-UV is calculated by solving a statically screened Bethe-Salpeter equation. Single-particle electron energies and wave functions are taken from ab initio electronic structure calculations. The screened electron-hole interaction W is calculated with a model dielectric function which includes the excited carriers. Though band-gap renormalization is neglected, dramatic changes are observed in the shape of {epsilon}{sub 2}({omega}) due to Pauli blocking and the enhanced screening of W. We estimate the error incurred in the static screening approximation by performing static screening calculations with the assumption that the excited carriers respond too slowly to screen W.

Authors:
Publication Date:
Sponsoring Org.:
(US)
OSTI Identifier:
40205562
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 63; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevB.63.075202; Othernumber: PRBMDO000063000007075202000001; 059107PRB; PBD: 15 Feb 2001
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BETHE-SALPETER EQUATION; DIELECTRIC MATERIALS; ELECTRONIC STRUCTURE; ELECTRONS; EXCITATION; RENORMALIZATION; SCREENS; SHAPE; VALENCE; WAVE FUNCTIONS

Citation Formats

Benedict, Lorin X. Dielectric function for a model of laser-excited GaAs. United States: N. p., 2001. Web. doi:10.1103/PhysRevB.63.075202.
Benedict, Lorin X. Dielectric function for a model of laser-excited GaAs. United States. doi:10.1103/PhysRevB.63.075202.
Benedict, Lorin X. 2001. "Dielectric function for a model of laser-excited GaAs". United States. doi:10.1103/PhysRevB.63.075202.
@article{osti_40205562,
title = {Dielectric function for a model of laser-excited GaAs},
author = {Benedict, Lorin X.},
abstractNote = {We consider a model for the ultrashort pulsed-laser excitation of GaAs in which electrons are excited from the top of the valence band to the bottom of the conduction band. The linear optical response of this excited system in the visible and near-UV is calculated by solving a statically screened Bethe-Salpeter equation. Single-particle electron energies and wave functions are taken from ab initio electronic structure calculations. The screened electron-hole interaction W is calculated with a model dielectric function which includes the excited carriers. Though band-gap renormalization is neglected, dramatic changes are observed in the shape of {epsilon}{sub 2}({omega}) due to Pauli blocking and the enhanced screening of W. We estimate the error incurred in the static screening approximation by performing static screening calculations with the assumption that the excited carriers respond too slowly to screen W.},
doi = {10.1103/PhysRevB.63.075202},
journal = {Physical Review B},
number = 7,
volume = 63,
place = {United States},
year = 2001,
month = 2
}
  • We have calculated the complex optical dielectric function of an electron-hole plasma in highly excited direct-gap semiconductors using the double-time Green's-function method. The equation of motion for an appropriate Green's function is linearized in the moment-conserving and Hartree-Fock approximations. Their interrelationship and the connection with earlier treatments of the electron-hole correlation is discussed. The electron-hole correlation yields an enhancement of the free-particle response and reproduces the overall shape of the observed gain and absorption spectra satisfactorily. The calculated changes in the refraction index with varying excitation energy exhibit a strong dispersive nonlinearity which explains the occurrence of optical bistability.
  • Epitaxial SrTiO{sub 3} films were grown on GaAs (001) substrates without any buffer layers using laser molecular beam epitaxy technique. The reflection high-energy electron diffraction observations have revealed that a layer-by-layer growth of SrTiO{sub 3} was achieved at optimized deposition conditions. The crystalline orientation of the as-grown SrTiO{sub 3} (001) films rotates 45 deg. in plane with respect to the GaAs substrates. Atomic force microscope studies show that these films possess atomically flat surfaces. The dielectric properties of the heterostructure were also investigated. Our results have clearly demonstrated the practicality of integrating perovskite oxide thin films with GaAs substrates.
  • An excited surface state on GaAs(110) has been investigated using a technique which populates the state with a laser pulse and measures its properties by time-resolved photoelectron spectroscopy using synchrotron radiation. Measurements of momentum, energy, and lifetime show that this is an intrinsic surface state near [ital [bar X]] in the surface Brillouin zone which equilibrates with bulk conduction electrons during the 5-ns pump pulse. The narrow photoelectron band increases linearly in kinetic energy with the probe photon energy, and no final-state effects appear in the limited energy range investigated.
  • Hot electrons and phonons excited in GaAs by subpicosecond laser pulses have been studied by inelastic light scattering for photoexcited electron densities varying between 10{sup 17} and 10{sup 19} cm{sup {minus}3}. Transient overshoot of longitudinal-optical (LO) phonon temperature above the electron temperature has been observed. This is explained by the fast production of zone-center LO phonons by hot electrons combined with slower reabsorption of the emitted phonons due to rapid cooling of {Gamma} valley electrons by intervalley scattering.