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Two excitation radiations were employed in measuring the Raman spectra of porous silicon-grown GaAs wirelike crystals. Redshifted and broadened transverse optic and longitudinal optic vibrational bands were observed. The vibrational band characteristics were found to be caused by a disorder-induced relaxation in Raman activity selection rules. The features are also attributed to penetration depth variations and defect density gradient.

It is a study of the transport properties parallel to the layers in the intentionally disordered doped GAAs/Al GaAs superlattices. It is reported that the mobility decreases with the increase of the disorder.

The electron properties of artificially disordered superlattices embedded in a wide AlGaAs parabolic well were investigated in a strong magnetic field. We demonstrated that in the extreme quantum limit the interlayer disorder results in formation of a new correlated phase. A nearly uniform electron distribution over the superlattice wells was found in a weak magnetic field. However, a nonuniform phase with partially localized electrons, representing well-developed fractional quantum Hall effect features, was observed in high magnetic field (at the filling factor ν < 1). A distinct magnetic field-induced transition separates these two phases. [ABSTRACT FROM AUTHOR]