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Linear and nonlinear photoeleastic coefficients in superlattices with tilted energy band profiles Host Publication: Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet Authors: R. Ayukhanov, G. Shkerdin, V. Kotov and J. Stiens Publication Year: 2007
Abstract: The influence of energy band tilting in quantum wells (QWs) on resonant photoelastic properties of superlattices near the ground exciton resonances has been theoretically studied. Analytic expressions for the dielectric permittivity and photoelastic constants were derived for two cases of inclined bandstructures: 1) due to an applied electric field and 2) due to a quasi-electric field in compositional graded QWs. For both cases it was shown that linear and nonlinear photoelastic constants depend on the factor 1/(L.lambda2), where L is the superlattice period, lamdba is the variation parameter calculated to determine the wave function and energy of the ground exciton state. It was shown that lambda lambda o for the case of an applied electric field. In the latter case, electrons and holes are driven in the opposite direction inside each quantum well and electron-hole pair localiza-tion decreases. On the contrary, electron-hole pair localization increases in the case of compositional grading. For this reason compositional grading of QWs results in an increase, whereas applied electrical fields lead to a de-crease of the resonant photoelastic constants. It was shown that the main con-tribution to the resonant photoelastic constants in superlattice structures near the exciton resonance is connected with the exciton energy modulation by the acoustic wave as a result of electron-phonon interaction via the deformation potential. Numerical calculations of the photoelastic constants with inclined QWs are presented for the case of GaAs/AlxGa1-xAs superlattices.
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