DETERMINATION OF LATTICE DISTORTION IN (GaAs)28(AlAs)24 SUPERLATTICE LAYERS BY X-RAY DIFFRACTION.

The structure of a (GaAs)//2//8(AlAs)//2//4 superlattice grown by MBE has been characterized in detail by X-ray diffraction. By applying a new method of Fourier analysis, both the concentration and lattice distortion modulations existing in the multilayer were determined on the basis of the integrated intensities of the satellite reflections around the (400) fundamental Bragg reflection. Both modulations were found to be like a step function. It is pointed out that the width of the boundary between the two regions should be narrow and less than two intermolecular layers. The spacings between successive cation layers were 2. 827 and 2. 835 A in the regions of GaAs and AlAl, respectively, along the (001) direction. This is in good agreement with the values calculated from the Poisson expansion model.