Nanoscale Structural and Emission Properties within - Russian Doll- - Type InGaN/AlGaN Quantum Wells

Due to the increasing desire for nanoscale optoelectronic devices with green light emission capability and high efficiency, ternary III- N- based nanorods are extensively studied. Many efforts have been taken on the planar device configuration, which lead to unavoided defects and strains. With selective- area molecular- beam epitaxy, new - Russian Doll- - type InGaN/AlGaN quantum wells (QWs) have been developed, which could largely alleviate this issue. This work combines multiple nanoscale characterization methods and k- p theory calculations so that the crystalline structure, chemical compositions, strain effects, and light emission properties can be quantitatively correlated and understood. The 3D structure and atomic composition of these QWs are retrieved with transmission electron microscopy and atom probe tomography while their green light emission has been demonstrated with room- temperature cathodoluminescence experiments. k- p theory calculations, with the consideration of strain effects, are used to derive the light emission characteristics that are compared with the local measurements. Thus, the structural properties of the newly designed nanorods are quantitatively characterized and the relationship with their outstanding optical properties is described. This combined approach provides an innovative way for analyzing nano- optical- devices and new strategies for the structure design of light- emitting diodes.The chemical components of the nanorods, shape effects and strain effects given by this unique - Russian Doll- - type geometry of InGaN/AlGaN quantum wells are quantitatively related with the optical properties. This combined approach reported here provides an innovative way for analyzing nano- optical- devices and new strategies for the structure design of light- emitting diodes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162759/3/adom202000481_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162759/2/adom202000481.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162759/1/adom202000481-sup-0001-SuppMat.pd

Urinary leukotriene E4 excretion: a biomarker of inflammatory bowel disease activity.

International audienceBACKGROUND: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders collectively referred to as inflammatory bowel diseases (IBD). Cysteinyl leukotrienes are proinflammatory 5-lipoxygenase-derived products that play a major role in the immune and inflammatory response. Consequently, they may be involved in the pathogenesis of IBD. The aim of this study was therefore to evaluate 1) the urinary excretion of leukotriene E(4) (LTE(4)) in IBD patients and healthy volunteers, and 2) the association between LTE(4) production and the activity (relapse/remission) of the disease. METHODS: IBD patients and healthy volunteers were prospectively recruited. CD and UC activity was determined on inclusion with the Crohn's Disease Activity Index and Clinical Activity Index, respectively. Urine was collected and the urinary excretion of LTE(4) was measured by liquid chromatography tandem mass spectrometry. RESULTS: 32 CD patients, 28 UC patients, and 30 controls were enrolled in the study. LTE(4) urinary excretion was significantly increased (P < 0.01) in CD [52.0 pg/mg creatinine (10th-90th percentiles: 26.2-148.0)] and UC [64.1 pg/mg creatinine (10th-90th percentiles: 26.7-178.0)] patients compared to controls [32.3 pg/mg creatinine (10th-90th percentiles: 21.8-58.8)]. LTE(4) levels were higher (P < 0.001) in patients with active disease than in patients in remission, for whom the levels of LTE(4) were similar to the levels of controls. CONCLUSIONS: Cysteinyl leukotriene pathway activation could contribute to the inflammation associated with IBD. The quantification of urinary LTE(4) could be an interesting noninvasive biomarker for the assessment of IBD activity

Defect free strain relaxation of microcrystals on mesoporous patterned silicon

A perfectly compliant substrate would allow the monolithic integration of high-quality semiconductor materials such as Ge and III-V on Silicon (Si) substrate, enabling novel functionalities on the well-established low-cost Si technology platform. Here, we demonstrate a compliant Si substrate allowing defect-free epitaxial growth of lattice mismatched materials. The method is based on the deep patterning of the Si substrate to form micrometer-scale pillars and subsequent electrochemical porosification. The investigation of the epitaxial Ge crystalline quality by X-ray diffraction, transmission electron microscopy and etch-pits counting demonstrates the full elastic relaxation of defect-free microcrystals. The achievement of dislocation free heteroepitaxy relies on the interplay between elastic deformation of the porous micropillars, set under stress by the lattice mismatch between Ge and Si, and on the diffusion of Ge into the mesoporous patterned substrate attenuating the mismatch strain at the Ge/Si interface

Chemical imaging of oxide confinement layers in GaAs/AlxGa1−xAs VCSELs

International audienceThe authors have studied the lateral oxidation of Al x Ga 1−x As layers buried in vertical-cavity surface-emitting lasers using cross-sectional scanning transmission electron microscopy coupled with electron energy loss spectroscopy. Chemical maps and composition profiles of the oxidized AlO x layers have been produced. The sensitivity is such that trace compositions of a few % As and Ga can be detected in the AlO x with a spatial resolution of a few nanometers on the recorded chemical maps. To demonstrate the performance of the mapping technique, we compare results from an area in the vertical-cavity surface-emitting laser (VCSEL) which is pure Al x Ga 1−x As to an oxidized area. These measurements are performed on a thin sample prepared by the focused ion beam technique within an actual VCSEL, which makes the mapping technique applicable for degradation investigations in devices at different stages of their lifetime. More generally, this measurement method is effective for detailed evaluation of AlO x layers and their fabrication process

Investigation of processing-induced defects in GaAs based vertical cavity surface emitting lasers with Al oxide confinement layers

International audienc