Growth And Characterization Of Gaalas/gaas And Gainas/inp Structures: The Effect Of A Pulse Metalorganic Flow

GaAlAs/GaAs and GaInAs/InP thick layers, single and multiple quantum wells were grown by atmospheric pressure metalorganic vapor phase epitaxy. Auger electron spectroscopy, wedge transmission electron microscopy, x-ray diffraction, low-temperature photoluminescence, and scanning electron microscopy were used to analyze the crystal quality. These analysis techniques show that layers grown using high vapor pressure metalorganic sources present fluctuations in the ternary alloy composition. We propose that these fluctuations are due to the pulse character of the high vapor pressure metalorganic flow. Bubbling experiments were performed to show the relationship between ternary layer composition fluctuation and the pulse character of the metalorganic flow. High vapor pressure metalorganic source like trimethylgallium presents tens of Angströms growth rate per pulse or bubble whereas a low vapor pressure source like triethylgallium presents few Angströms growth rate per bubble.71117918

Triketone toxicity: A report on two cases of sulcotrione poisoning

INTRODUCTION: Sulcotrione is a herbicidal agent belonging to the family of triketones. Sulcotrione herbicides are used for weed control in maize and flax crops. To date, no cases of human poisoning had been reported in the literature linked to different herbicidal agents in the triketone family. We report here on two cases of the voluntary ingestion of this substance in the form of the branded product Mikado(TM), which were recorded by the Angers Poison Centre. CASE REPORT: Both cases of voluntary ingestion constituted attempted suicide, and involved two men aged 30 and 37 years. Their symptoms linked to sulcotrione were limited to vomiting, despite elevated plasma concentrations of sulcotrione. In one case, hypertyrosinemia has been demonstrated. The outcome was favourable in both patients and at follow up, no ocular disorders were observed. In the second case, hypotension and transient renal failure could be linked to the concomitant ingestion of chlorophenoxy herbicides. DISCUSSION: In animal toxicity studies, sulcotrione inhibit 4-hydro-phenylpyruvate dioxygenase leading to hypertyrosinemia and corneal opacities. In both cases, no ocular disorders were observed despite hypertyrosinemia in one case. These case reports were consistent with the animal toxicology findings concerning triketones, and particularly their relative safety in mammals following acute poisoning. However it seems prudent to monitor plasma tyrosine concentrations and to screen prospectively for corneal deposits if further acute intoxication events occur

Temperature-dependence of exciton radiative recombination in (Al,Ga)N/GaN quantum wells grown on a-plane GaN substrates

This article presents the dynamics of excitons in a-plane (Al,Ga)N/GaN single quantum wells of various thicknesses grown on bulk GaN substrates. For all quantum well samples, recombination is observed to be predominantly radiative in the low-temperature range. At higher temperatures, the escape of charge carriers from the quantum well to the (Al,Ga)N barriers is accompanied by a reduction in internal quantum efficiency. Based on the temperature-dependence of time-resolved photoluminescence experiments, we also show how the local disorder affects the exciton radiative lifetime at low temperature and the exciton non-radiative lifetime at high temperature.We acknowledge financial support from the Swiss National Science Foundation through Project No. 129715 and from the Polish National Science Center (Project DEC-2011/ 03/B/ST3/02647). The work was partially supported by the European Union within European Regional Development Fund through Innovative Economy Grant No. POIG.01.01.02-00-008/08. P.C. also acknowledges financing from the European Union Seventh Framework Program under grant agreement No. 265073

Density dependence of carrier-carrier-induced intersubband scattering in GaAs/AlxGa1-xAs quantum wells

Photoluminescence lifetimes of the n = 2 level in a large quantum well show a clear nonmonotonic dependence on the density of optically generated carriers. Varying the power density over five orders of magnitude we prove directly the high efficiency of carrier-carrier interaction for intersubband scattering when longitudinal-optical phonon emission is suppressed. For low densities, the observed n = 2 decay times get shorter (from 40 down to 5 ps) as the density is increased. At high densities Pauli blocking reduces significantly the intersubband scattering rates. [S0163-1829(99)06124-X]