HIGH-RESOLUTION X-RAY-DIFFRACTION AND X-RAY STANDING-WAVE ANALYSES OF(ALAS)(M)(GAAS)(N) SHORT-PEROID SUPERLATTICES

X-ray diffraction has been extended by simultaneously measuring inelas tic signals excited internally by the x-ray standing wave field. As in elastic x-ray standing wave signal we recorded the photoelectron curre nt from an (AlAs)(m)(GaAs)(n) short-period superlattice on a GaAs(001) substrate. it shows clear modulations due to the GaAs(004) substrate reflection, the (AlAs)(GaAs)(004; 0) superlattice main reflection and the thickness fringes. The modulation at the (AlAs)(GaAs)(004; 0) refl ection is related to the content of atoms in lattice plane positions. This is of technological interest, since the coherent fraction offers a new parameter for the characterization of the quality of short-perio d superlattices. The x-ray diffraction measurement to a wide angular r ange gives the complete set of satellites between two neighbouring sub strate reflections. For some of the samples investigated, a non-coinci dence of the (AlAs)(GaAs) satellite groups belonging to GaAs(002) and GaAs(004) is observed, which can be shown to be due to an incommensura te modulation of the superlattice. From the satellite intensities, the Fourier coefficients of the modulation can be determined by compariso n with kinematical diffraction theory. This gives a description of the (AlAs)(m)(GaAs)(n) superlattice unit cell and its interface widths.