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The growth of AlGaAsSb materials on InP substrate was carried out by elemental source molecular beam epitaxy (MBE). The control of group-V composition appeared complex. In order to minimize the fluctuations of group-V composition, its dependence on growth temperature, cracking of the group-V species, growth rate and AlGaratio were evaluated. Then we focused on AlAsxSb1−xand AlzGa1−zAsySb1−yalloys with xand yallowing lattice matching to InP, and with zaround 0.10 in order to have transparency at 1.55 μm. Pairing these alloys, we built up Bragg mirrors with the reflectivity centered at 1.55 μm. A mirror consisting of 2012pairs exhibited a reflectivity of 99.8% with a 200 nm stopband width. Doping studies of these materials demonstrated n- and p-type conductivities with carrier concentrations over 1019cm−3where Te and Be were, respectively, the n- and p-type dopants.

A recombinant plasmid encoding rat preproinsulin I was encapsulated in large liposomes and intravenously injected in rats. Glycemia and blood, splenic, and hepatic insulin were assayed at various times beginning 6 hr after inoculation. The results were compared with controls that had received (i) empty liposomes, (ii) liposomes carrying the Escherichia coli pBR322 plasmid, (iii) the free rat insulin I gene, and (iv) no injection at all. Whereas all controls showed unchanged glucose and insulin levels, the treated animals had, 6 hr after inoculation, a blood glucose level of 72 +/- 5 mg of glucose/100 ml of blood as compared with 107 +/- 2 mg/ml for controls. Radioimmunoassay of blood insulin gave 61 +/- 8 microunits/ml as compared with 43 +/- 5 microunits/ml for controls and the spleen and liver values were 242 +/- 22 and 204 +/- 20 microunits/g of tissue, respectively, as compared with 112 +/- 20 and 87 +/- 15 microunits/g in controls. External gamma-camera imaging of the organ uptake of 111In-labeled liposomes permitted study of the kinetics and extent of uptake of the liposomes by spleen and liver, results that support the findings concerning insulin synthesis in the two organs.

The aim of this work is to characterize the electrical properties of the defects induced by hafnium (Hf) contamination in silicon by means of different experimental techniques. Hf is introduced in silicon by shallow ion implantation at low doses in order to match experimental conditions close to an accidental contamination; moreover annealing is performed in RTP, that allows to maintain the metallic contaminant in solution. During the annealing the most part of Hf atoms segregate at the SiO2/Si interface, increasing the density of interface states. A detectable part of Hf atoms diffuse through the silicon bulk producing generation and recombination centers and traps for holes and electrons. Eight levels are detected, six in the upper and two in the lower half of the silicon bandgap, respectively. Hf acts differently in p- or n-type substrates: it is more effective as hole trap and as a recombination center in p-type and it de-activates above an implanted dose of 3 × 1011cm−2only in p-type silicon. The accurate determination of Hf-induced defects even at low concentration allows to find and pinpoint possible hafnium contamination affecting electronic devices.

AlAsxSb(1-x)/Al0.13Ga0.87AsySb(1-y) quarter-wave distributed Bragg stacks were grown on an InP substrate. With 15 pairs of layers, a peak reflectivity > 0.98 around 1.55 µm was measured. The refractive index for each material was deduced from reflectivity measurements. We found n = 3.65 for Al0.13Ga0.87AsySb(1-y) and n = 3.11 for AlAsxSb(1-x).