PICOSECOND CARRIER CAPTURE BY A SEPARATE CONFINEMENT LASER STRUCTURE

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Serum magnesium and calcium levels in relation to ischemic stroke : Mendelian randomization study

ObjectiveTo determine whether serum magnesium and calcium concentrations are causally associated with ischemic stroke or any of its subtypes using the mendelian randomization approach.MethodsAnalyses were conducted using summary statistics data for 13 single-nucleotide polymorphisms robustly associated with serum magnesium (n = 6) or serum calcium (n = 7) concentrations. The corresponding data for ischemic stroke were obtained from the MEGASTROKE consortium (34,217 cases and 404,630 noncases).ResultsIn standard mendelian randomization analysis, the odds ratios for each 0.1 mmol/L (about 1 SD) increase in genetically predicted serum magnesium concentrations were 0.78 (95% confidence interval [CI] 0.69-0.89; p = 1.3 7 10-4) for all ischemic stroke, 0.63 (95% CI 0.50-0.80; p = 1.6 7 10-4) for cardioembolic stroke, and 0.60 (95% CI 0.44-0.82; p = 0.001) for large artery stroke; there was no association with small vessel stroke (odds ratio 0.90, 95% CI 0.67-1.20; p = 0.46). Only the association with cardioembolic stroke was robust in sensitivity analyses. There was no association of genetically predicted serum calcium concentrations with all ischemic stroke (per 0.5 mg/dL [about 1 SD] increase in serum calcium: odds ratio 1.03, 95% CI 0.88-1.21) or with any subtype.ConclusionsThis study found that genetically higher serum magnesium concentrations are associated with a reduced risk of cardioembolic stroke but found no significant association of genetically higher serum calcium concentrations with any ischemic stroke subtype

COOLING REDUCTION DUE TO A RAPID DENSITY DECAY OF HOT CARRIERS IN GAAS

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Ultrafast carrier dynamics at a metal-semiconductor interface

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Band-structure modifications due to photogenerated carriers in a GaAs/AlxGa1-xAs heterostructure

We have investigated, by means of photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy, the carrier-induced band-structure modifications of a GaAs/AlxGa1-xAs heterostructure containing a two-dimensional electron gas (2DEG). The PL spectra are dominated by an intense recombination line which originates from the 2DEG and which is blueshifted as a function of excitation density. In the PLE spectra, we observe excitonic transitions to unoccupied states of the 2DEG that are also slightly blueshifted. By comparison with self-consistent calculations of the subband structure of the electrons and holes, the origin of the observed transitions can be unambiguously determined. We developed a model in which the carrier-induced band-structure modifications can be calculated, taking into account the contribution of the photogenerated excess carriers. The dominant mechanism which causes the blueshift of the PL spectra is the change of the electrostatic potential due to the buildup of holes, separated in real space from the excess electrons in the 2DEG

Spatial variations of photoluminescence line broadening around oval defects in GaAs/AlGaAs multiple quantum wells

The authors have investigated spatially resolved photoluminescence spectra around several alpha - and lambda -type oval defects in GaAs/AlGaAs multiple-quantum-well structures. In their low-temperature photoluminescence set-up they combine a high spectral resolution with a 2 mu m spot size on the sample. In the alpha -type defects the authors observe a 25-45 meV low-energy tail of the main quantum well recombination peak near the core of the oval defect as well as an approximately 1 meV line broadening originating from two regions which are symmetrically located at either side of the (110) symmetry axis of the defect. These line-broadening effects are explained by vertical growth rate variations within the oval defect

A novel mechanism for light-activated switching in pseudomorphic heterostructures

We propose a novel physical mechanism based on light-activated band structure modifications in pseudomorphic heterostructures which can be employed for a light-activated optical switch or a light-activated all-optical modulator. These modifications have been tested by measuring the blue shift of higher subbands in a modulation doped GaAs/AlxGa1-xAs heterostructure containing a two-dimensional electron gas (2DEG). The mechanism can be employed in room temperature devices when the absorption and the blue shift of the excited states of the 2DEG are optimized by tailoring the design of the pseudomorphic heterostructure. All-optical modulation with a contrast ration 27:1 is predicted by our model calculations