A new boundary condition is employed in the kinematical model analysis of Bragg-peak profiles of layered single crystals, which is the dynamical reflection amplitude of the substrate instead of the previously used dynamical intensity. It is shown that this boundary condition properly accounts for the angular shift effect in the Bragg-peak profile of very thin epitaxial layers and superlattices. A kinematical model simulates properly the interference profiles in the C-layer Bragg peak of C/A/C/sub-type samples, but not in the B-layer Bragg peak of the B/A/B-type samples. The simulated and experimental rocking curves for the thin single-layer AlGaAs/GaAs and GaInAs/InP samples and for an AlGaAs/GaAs superlattice sample are discussed. Rocking curves are simulated by using the dynamical diffraction theory and the kinematical model with the old or new boundary condition. A matrix method for the dynamical theory superlattice simulation is also presented. The superlattice simulation using this matrix method is found to be substantially faster than the conventional recursive formula approach.

We have characterized, using the interference structure in x-ray rocking curves, a single or double strained GaInP layer grown on an InP substrate. The measured GaInP layer thicknesses are 9±3 Å and 107±3 Å for the single strained layer samples and 7 Å/50 Å and 32 Å/32 Å for the double strained layer samples. The rocking curve results for the 107 Å single-barrier sample and the 7 Å/50 Å double-barrier sample agreed well with the cross-section transmission electron microscopy data and the secondary-ion mass spectrometry data. The x-ray interference structure for the single strained barrier samples indicates the existence of many half-monolayer steps within the 1×1 mm2 x-ray beam spot at each GaInP/InP interface.

We report on a new method for the generation of phosphorus beams in molecular beam epitaxy: the use of a valved, solid cracker source. The valved solid source avoids previous difficulties associated with the use of solid phosphorus, and provides an attractive alternative to the use of phosphine. The use of red phosphorus does not interfere with the subsequent growth of high quality arsenides in the same growth chamber. The performance of this valved phosphorus source is illustrated by the growth of two ternary phosphides, Ga0.5In0.5P and Al0.5In0.5P. The quality of the phosphides reported here is comparable to the best results reported by other growth techniques. The effects of composition, growth temperature, and P2 flux on the films’ characteristics are reported. Indium desorption during growth is found to be substantially greater in AlInP than in GaInP.

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Synthesis and Second-Order Nonlinear Optical Properties of Polymethacrylates Containing Organic Salt Dye Chromophore.-In view of the interest in side-chain polymers as potential candidates for application in electrooptic and photonic devices, new methacrylate polymers containing the N-alkylpyridinium salt at the side chain are prepared by polymerization of the monomers (VII) and (XIII) in the presence of AIBN. These molecular ionic polymers can be successfully poled and show a large second-order nonlinear optical susceptibility. The presence of an ionic salt chromophore in the side chain results in an increase in the glass transition temp. and therefore an improved temporal stability, which seems better than that of some guest-host systems. -(CHOI, D. H.; KIM, H. M.; WIJEKOON, W. M. K. P.; PRASAD, P. N.; Chem.