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Liquid phase epitaxial layers of InxGa1−xAsyP1−y grown lattice matched to InP〈001〉 substrates, in the concentration range 0.53⩽x⩽0.88, have been studied by transmission electron microscopy. For the usual growth temperatures, solid instability was predicted for compositions in the range 0.55≲x≲0.75. Indeed a quasiperiodic variation of a strain contrast, though very light in some cases, is always observed in the 〈100〉 and 〈010〉 directions in that composition range, and never outside. The pseudoperiodicity is of the order of 1000 Å. Local concentration measurements have been performed on one sample using a scanning transmission electron microscope. They show that the strain contrast, quite strong in that sample, is related to a concentration modulation. The measured variations on x and y are as high as 0.1, and they keep the ratio x/y constant, which is consistent with phase separation observed on nucleated InxGa1−xAsyP1−y.

All-optical bistability is demonstrated in GaAs/AlGaAs multiple quantum well microresonators fabricated by SiCl4 reactive ion etching. A fabrication process has been developed in order to obtain low threshold bistability. The studied samples are two-dimensional 15×15 arrays of cylindrical microresonators of 4 μm diam and 6 μm height. Owing to lateral carrier and light confinement, bistability is observed with a strongly reduced threshold power, below 100 μW. This result was obtained without post-etching surface treatment. The low bistability threshold suggests that the surface recombination rate is reasonably small, possibly due to some self-passivation occurring during the etching process.

Heterojunctions GaAs-AlxGa~_~As involved in the elaboration of IR laser diodes have been studied. The difference in lattice parameter between the GaAs substrate and the aluminum-substituted epitaxic layer AlxGa~_~As has been measured accurately on a double-crystal spectrometer for a series of compositions. These data coupled with radius of curvature determination have permitted calculation of the stress in the layer and the bulk lattice parameter of AI~Ga~_~As. Characterization of the defects introduced during the liquid-phase epitaxy has been performed by X-ray topography.

Impurity segregation in explosively crystallized a-Si presents two different behaviors depending on whether the intermediate liquid phase in the explosive process is large or narrow. This confirms the theories already published. In other words, a-Si explodes in a way similar to a-Ge. a-Si, however, presents a specific type of explosive crystallization explained by its higher nucleation rate with respect to a-Ge.

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A comprehensive study of AuMn ohmic contact for p-type GaAs is presented using electrical testing, scanning electron microscopy, Auger electron spectroscopy, and secondary ion-mass spectroscopy. The contact fabrication-Mn proportion against Au, alloying cycle-was optimized taking into account the results of the electrical tests. Contact resistivity values are presented for different doping levels. Unalloyed AuMn contact was found to give a good contact resistivity on samples with an ultrahigh doping level of2 X 1

Articles you may be interested inOne-dimensional effects in quantum wires made from a double heterojunction based on the AlAs/GaAs system J.Optically confirmed twodimensional confinement effects in ultranarrow InGaAs/InP quantum well wires AIP Conf. Proc. 227, 50 (1991); 10.1063/1.40621Onedimensional subbands and mobility modulation in GaAs/AlGaAs quantum wires Appl.