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We report the observation of magnetophonon resonances on the background of the longitudinal magnetoconductance in short-period GaAs/AlAs semiconductor superlattices. Both the GaAs and the AlAs longitudinal optical phonons are observed. We show how the enhancement of the magnetophonon effect with electric field is connected to the shift of the electron distribution towards the high-velocity and low-density-of-states region at the midpoint of the reduced Brillouin zone. The observed temperature dependence can be explained by considering the competition between the phonon population and the electron lifetime. The two superposed series of the GaAs and the AlAs optical phonons are shifted when hydrostatic pressure is applied and the relative strength of each series changes as the ⌫ miniband comes closer to the X states.

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The vertical magnetotransport properties of GaAs–AlAs superlattices have been investigated as a function of the in-plane magnetic field orientation. Two main effects were observed: (i) the influence of the roughness anisotropy with respect to the crystallographic orientation, and (ii) the nonparabolicity of the energy in the plane of the layers. The interface fluctuations induced a modulation of the miniband transport with a period of 180°. The nonparabolic energy of the deflected electronic orbits also induced a modulation of the vertical transport but with a period of 90°. Both observed effects are in qualitative agreement with a semiclassical description of the Boltzmann transport equation.

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