Electron and trap dynamics in As-ion-implanted and annealed GaAs

The ultrafast dynamics of As-ion-implanted and annealed GaAs is investigated using transmission pump–probe measurements.Carrier recombination time was found to increase from 4 to 40 ps with increasing annealing temperature. At lower annealing temperatures, the transmitted optical signal is dominated by induced absorption and at higher annealing temperatures this effect is replaced by induced transparency.This work was supported in part by the EC INCOCOPERNICUS project ‘‘DUO—devices for ultrafast optoelectronics’’ and the Lithuanian Science and Study Foundation

Proceedings of the inaugural International Summit for Medical Nutrition Education and Research

© 2016 The Royal Society for Public Health Medical Nutrition Education (MNE) has been identified as an area with potential public health impact. Despite countries having distinctive education systems, barriers and facilitators to effective MNE are consistent across borders, demanding a common platform to initiate global programmes. A shared approach to supporting greater MNE is ideal to support countries to work together. In an effort to initiate this process, the Need for Nutrition Education/Innovation Programme group, in association with their strategic partners, hosted the inaugural International Summit on Medical Nutrition Education and Research on August 8, 2015 in Cambridge, UK. Speakers from the UK, the USA, Canada, Australia, New Zealand, Italy, and India provided insights into their respective countries including their education systems, inherent challenges, and potential solutions across two main themes: (1) Medical Nutrition Education, focused on best practice examples in competencies and assessment; and (2) Medical Nutrition Research, discussing how to translate nutrition research into education opportunities. The Summit identified shared needs across regions, showcased examples of transferrable strategies and identified opportunities for collaboration in nutrition education for healthcare (including medical) professionals. These proceedings highlight the key messages presented at the Summit and showcase opportunities for working together towards a common goal of improvement in MNE to improve public health at large

Suppression of thermal atomic interdiffusion in C-doped InGaAs∕AlGaAs quantum well laser structures using TiO₂ dielectric layers

The effects of thermal annealing on C-doped InGaAs∕AlGaAs quantum well laser structures capped with titanium dioxide (TiO₂) layers were investigated. The atomic interdiffusion was greatly suppressed by the presence of a TiO₂ capping layer during annealing, inhibiting even the thermal intermixing observed in the uncapped sample. An increase in the amount of lattice contraction associated with the presence of substitutional carbonCAs after annealing without a capping layer was observed, but not after annealing with a TiO₂ capping layer. Capacitance–voltage measurements confirmed the electrical activation of carbon after annealing without a dielectric layer and show a negligible change after annealing using a TiO₂ capping layer. The possible mechanisms involving both the atomic intermixing on the group III sublattice and carbon activation on the group V sublattice and the implications for optoelectronic device integration using impurity-free intermixing are discussed.P.L.G. acknowledges the scholarship funded by the Australian Agency for International Development (AusAID). Australian Research Council is gratefully acknowledged for the financial support

A study of quantum well solar cell structures with bound-to-continuum transitions for reduced carrier recombination

A bound-to-continuum quantum well solar cell structure is proposed, and the band structure and absorption spectra are analyzed by the use of an eight band k⋅p model. The structure is based on quantum wells that only support bound states for the valence band. The absence of bound conduction band states has a number of potential advantages, including a reduction of electron trapping and, therefore, a reduction of quantum well induced photocarrier recombination due to reduced spatial overlap of the electron and hole wavefunctions.Thanks are due to the Australian Research Council for the financial support of this research

Enhanced optical properties of the GaAsN/GaAs quantum-well structure by the insertion of InAs monolayers

Microstructural and optical properties of InAs-inserted and reference single GaAsN/GaAs quantum-well (QW) structures grown by metalorganic chemical vapor deposition were investigated using cross-sectional transmission electron microscopy and photoluminescence (PL). Significant enhancement of PL intensity and a blueshift of PL emission were observed from the InAs-inserted GaAsN/GaAs QW structure, compared with the single GaAsN/GaAs QW structure. Strain compensation and In-induced reduction of N incorporation are suggested to be two major factors affecting the optical properties.The authors would like to thank the Commonwealth Department of Education, Science, and Training and the Australian Research Council for their financial support

Temperature dependence of photoluminescence from single core-shell GaAs–AlGaAs nanowires

Temperature-dependent polarized microphotoluminescencemeasurements of single GaAs∕AlGaAs core-shell nanowires are used to probe their electronic states. The low-temperature emission from these wires is strongly enhanced compared with that observed in bare GaAsnanowires and is strongly polarized, reflecting the dielectric mismatch between the nanowire and the surrounding air. The temperature-dependentband gap of the nanowires is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 120K, with an activation energy of 17meV reflecting the presence of nonradiative defects.This work was supported by the University of Cincinnati. Australian authors gratefully acknowledge the financial support from the Australian Research Council

Diabetes eye screening in urban settings serving minority populations: detection of diabetic retinopathy and other ocular findings using telemedicine.

IMPORTANCE: The use of a nonmydriatic camera for retinal imaging combined with the remote evaluation of images at a telemedicine reading center has been advanced as a strategy for diabetic retinopathy (DR) screening, particularly among patients with diabetes mellitus from ethnic/racial minority populations with low utilization of eye care. OBJECTIVE: To examine the rate and types of DR identified through a telemedicine screening program using a nonmydriatic camera, as well as the rate of other ocular findings. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional study (Innovative Network for Sight [INSIGHT]) was conducted at 4 urban clinic or pharmacy settings in the United States serving predominantly ethnic/racial minority and uninsured persons with diabetes. Participants included persons aged 18 years or older who had type 1 or 2 diabetes mellitus and presented to the community-based settings. MAIN OUTCOMES AND MEASURES: The percentage of DR detection, including type of DR, and the percentage of detection of other ocular findings. RESULTS: A total of 1894 persons participated in the INSIGHT screening program across sites, with 21.7% having DR in at least 1 eye. The most common type of DR was background DR, which was present in 94.1% of all participants with DR. Almost half (44.2%) of the sample screened had ocular findings other than DR; 30.7% of the other ocular findings were cataract. CONCLUSIONS AND RELEVANCE: In a DR telemedicine screening program in urban clinic or pharmacy settings in the United States serving predominantly ethnic/racial minority populations, DR was identified on screening in approximately 1 in 5 persons with diabetes. The vast majority of DR was background, indicating high public health potential for intervention in the earliest phases of DR when treatment can prevent vision loss. Other ocular conditions were detected at a high rate, a collateral benefit of DR screening programs that may be underappreciated

Direct imaging of the spatial diffusion of excitons in single semiconductor nanowires

We use spatially and temporally resolved photoluminescence to measure excitondiffusion in single zinc blende GaAs/AlGaAs core/shell and mixed phase InPnanowires.Excitons in the single phase GaAs/AlGaAs nanowires are seen to diffuse rapidly throughout the nanowire with a measured diffusion constant ranging from 45 to 100 cm²/s, while in the mixed phase, InPnanowireelectrons and holes are seen to rapidly localize to the quantum confined states in the zinc blende and wurtzite segments, respectively. The diffusion constant in the GaAs/AlGaAs nanowire is similar to the best hole mobilities observed in modulation doped heterostructures.We acknowledge the financial support of the National Science Foundation through grants DMR-0806700, 0806572, 1105362, 1105121, and ECCS-1100489, and the Australian Research Council