[en] Thin films of A15 Nb₃Al have been prepared by reactive diffusion of sputter-deposited Nb/Al multilayers. The diffusion reactions were studied by in situ annealing x-ray diffraction in the temperature range 50--950 ⁰C. Initially the Nb and Al sublayers react to form the phase NbAl₃. This interface reaction prevents the formation of the sigma-phase Nb₂Al, frequently found as a second phase in A15 Nb₃Al materials; NbAl₃ reacts with the remaining Nb to form the A15 phase. The highest T/sub c/, 16.2 K measured resistively and 15.2 K inductively, was found in a Nb/Al multilayer with an A15 cell parameter a₀ = 5.195 A which corresponds to approx.20 at. % Al. From a comparison with previous investigations of the T/sub c/ dependence on Al concentration and A15 cell parameter, it is concluded that a small amount of the A15 phase has a higher composition of 22--23 at. % Al

[en] Thin films of A15 Nb₃Sn have been prepared by reactive diffusion of sputter-deposited Nb/Sn multilayers. The layer thicknesses were arranged in such a way as to produce Nb₃Sn and desired off-stoichiometry samples. The reaction was studied by means of in situ temperature-dependent X-ray analysis in the range 50⁰C-950⁰C. It was observed that, prior to the formation of the A15 phase, a very rapid reaction takes place between the Nb sublayers and molten Sn. In this reaction a new phase was observed which could be interpreted as a hexagonal Laves phase NbSn₂. This phase transforms into orthorhombic NbSn₂ which then reacts with the remaining Nb to form A15 Nb₃Sn. The fact that the reaction occurs at the Nb/liquid Sn interface with the formation of the most Sn-rich phase indicates that the reaction takes place by diffusion of Nb into liquid Sn. The highest superconducting transition temperature was found to be 17.45⁰K. The values of the A15 cell parameters indicated that the diffusion reaction of both onand off - stoichiometry Nb₃Sn multilayers is driven towards the Sn-rich side of Nb₃Sn, with a maximum composition range of 24-28 at% Sn

[en] This paper reports that ultra-high Be doping of Ga_0.47In_0.53As layers grown by gas source molecular beam epitaxy has shown that for each growth temperature there exists a maximum hole concentration ≥1 x 10²⁰cm^-3. Increasing the Be flux above that which produces the maximum hole concentration results in a degradation of the crystalline quality of the films. The degradation of film quality results from precipitation of a Be-rich phase on the surface during growth and nucleation of dislocations at each precipitate. Below that concentration, some of the Be segregates and floats on the growing surface

[en] We demonstrate a combination of focused Ga beam writing and dry etching techniques to pattern InP wafers in a common vacuum chamber. Surface steps on the order of 1000 A can be efficiently prepared using moderate Ga ion fluences. The implanted areas exhibit a faster etch rate, even for Ga doses below /similar to/10¹⁴ cm^-2. The implantation damage is removed by the low-energy Cl-assisted ion beam etching as shown by the high quality of p-n junctions grown on etched surfaces. GaInAs/InP heterostructures grown on in situ patterned substrates show excellent morphology and high luminescence efficiency

[en] The authors demonstrate a vacuum lithography process which uses a finely focused Ga ion beam to write the pattern which is then transferred to the InP pattern by low energy dry etching. Surface steps on the order of 1000-2000 Angstrom in height, and lateral resolution limited only by size of the ion beam, can be efficiently prepared using moderate Ga ion fluences. The surfaces prepared by this process are damage free and suitable for epitaxial overgrowth. GaInAs/InP heterostructures grown on in-situ patterned substrates show excellent morphology and high luminescence efficiency

[en] This paper reports on dynamical X-ray diffraction studies that have been carried out for lattice-matched InGaAs/InP superlattices grown by modified molecular beam epitaxy (MBE) techniques. The (400) X-ray satellite pattern, which is predominantly affected by the strain modulation, was analyzed. The strain and thickness of the actual layers including the presence of strained interfacial regions were determined

[en] An abrupt transition in the growth mode is observed for epitaxial films of In P prepared by metalorganic molecular beam epitaxy. Below a minimum growth temperature, T^min_g, three-dimensional growth and kinetically controlled roughening are observed, with surface roughness showing two distinct power law regimes dependent on film thickness. The observed roughening is attributed to the presence of a Schwoebel-Erlich-type barrier to adatom motion across surface steps. From the dependence of T^min_g on the substrate misorientation, we are able to estimate an upper limit of 0.4-O.5 e V for this barrier. At temperatures higher than T^min_g, we observe smooth morphologies with the concurrent of localized defects associated with P-vacancies. The density of defects is strongly dependent on the thermodynamic and kinetic growth parameters. (author). 18 refs., 6 figs