The Effect of Imbalanced Carrier Transport on the Efficiency Droop in GaInN-Based Blue and Green Light-Emitting Diodes

The effect of strongly-imbalanced carrier concentration and mobility on efficiency droop is studied by comparing the onset voltage of high injection, the onset current density of the droop, and the magnitude of the droop, as well as their temperature dependence, of GaInN-based blue and green light-emitting diodes (LEDs). An n-to-p asymmetry factor is defined as sigma(n)/sigma(p), and was found to be 17.1 for blue LEDs and 50.1 for green LEDs. Green LEDs, when compared to blue LEDs, were shown to enter the high-injection regime at a lower voltage, which is attributed to their less favorable p-type transport characteristics. Green LEDs, with lower hole concentration and mobility, have a lower onset current density of the efficiency droop and a higher magnitude of the efficiency droop when compared to blue LEDs. The experimental results are in quantitative agreement with the imbalanced carrier transport causing the efficiency droop, thus providing guidance for alleviating the phenomenon of efficiency droop.114sciescopu

Enhanced overall efficiency of GaInN-based light-emitting diodes with reduced efficiency droop by Al-composition-graded AlGaN/GaN superlattice electron blocking layer

AlxGa1-xN/GaN superlattice electron blocking layers (EBLs) with gradually decreasing Al composition toward the p-type GaN layer are introduced to GaInN-based high-power light-emitting diodes (LEDs). GaInN/GaN multiple quantum well LEDs with 5- and 9-period Al-composition-graded AlxGa1-xN/GaN EBL show comparable operating voltage, higher efficiency as well as less efficiency droop than LEDs having conventional bulk AlGaN EBL, which is attributed to the superlattice doping effect, enhanced hole injection into the active region, and reduced potential drop in the EBL by grading Al compositions. Simulation results reveal a reduction in electron leakage for the superlattice EBL, in agreement with experimental results. (C) 2013 AIP Publishing LLC.open1133sciescopu

EHR-SeqSQL : A Sequential Text-to-SQL Dataset For Interactively Exploring Electronic Health Records

In this paper, we introduce EHR-SeqSQL, a novel sequential text-to-SQL dataset for Electronic Health Record (EHR) databases. EHR-SeqSQL is designed to address critical yet underexplored aspects in text-to-SQL parsing: interactivity, compositionality, and efficiency. To the best of our knowledge, EHR-SeqSQL is not only the largest but also the first medical text-to-SQL dataset benchmark to include sequential and contextual questions. We provide a data split and the new test set designed to assess compositional generalization ability. Our experiments demonstrate the superiority of a multi-turn approach over a single-turn approach in learning compositionality. Additionally, our dataset integrates specially crafted tokens into SQL queries to improve execution efficiency. With EHR-SeqSQL, we aim to bridge the gap between practical needs and academic research in the text-to-SQL domain. EHR-SeqSQL is available at https://github.com/seonhee99/EHR-SeqSQL.Comment: ACL 2024 (Findings

CheckEval: Robust Evaluation Framework using Large Language Model via Checklist

We introduce CheckEval, a novel evaluation framework using Large Language Models, addressing the challenges of ambiguity and inconsistency in current evaluation methods. CheckEval addresses these challenges by dividing evaluation criteria into detailed sub-aspects and constructing a checklist of Boolean questions for each, simplifying the evaluation. This approach not only renders the process more interpretable but also significantly enhances the robustness and reliability of results by focusing on specific evaluation dimensions. Validated through a focused case study using the SummEval benchmark, CheckEval indicates a strong correlation with human judgments. Furthermore, it demonstrates a highly consistent Inter-Annotator Agreement. These findings highlight the effectiveness of CheckEval for objective, flexible, and precise evaluations. By offering a customizable and interactive framework, CheckEval sets a new standard for the use of LLMs in evaluation, responding to the evolving needs of the field and establishing a clear method for future LLM-based evaluation.Comment: HEAL at CHI 202

Relationship between unemployment, depression, and suicide during COVID-19 among males in South Korea: based on internet search trends

Background: The economic recession caused by the COVID-19 pandemic has led to significant increases in unemployment rates, which negatively affect mental health and contribute to higher rates of depression and suicide. Recent analyses of internet search trends indicate an increased public interest in these mental health issues, promoting efforts to implement web-based interventions. Methods: This study investigated the mediating effects of depression on the relationship between unemployment and suicide in South Korea during COVID-19 by analyzing internet search trends. The search volume of keywords related to unemployment, depression, and suicide during the COVID-19 period (from 21 January 2020, to 11 May 2023) was extracted from South Korea’s largest online search engine data, including searches conducted on both mobile and desktop devices. The study sample included of working-age adult males between the ages of 20 and 60. The search volume data from 1207 search volume entries were extracted and analyzed using SPSS PROCESS macro (version 4.0). Results: The analysis revealed that suicide-related searches had the highest relative frequency, followed by depression and unemployment. Unemployment was found to significantly affect depression, and depression-related keyword searches mediated the association between unemployment- and suicide-related keyword searches. Conclusions: The findings suggest that government policies should prioritize both economic recovery efforts, and mental health support, including unemployment assistance, wage support and suicide prevention services. Developing web-based mental health resources and interventions could strengthen these efforts

Energy bandgap variation in oblique angle-deposited indium tin oxide

Indium tin oxide (ITO) thin films deposited using the oblique angle deposition (OAD) technique exhibit a strong correlation between structural and optical properties, especially the optical bandgap energy. The microstructural properties of ITO thin films are strongly influenced by the tilt angle used during the OAD process. When changing the tilt angle, the refractive index, porosity, and optical bandgap energy of ITO films also change due to the existence of a preferential growth direction at the interface between ITO and the substrate. Experiments reveal that the ITO film's optical bandgap varies from 3.98 eV (at normal incident deposition) to 3.87 eV (at a 60 tilt angle). 2-10 OAD is generally associated with physical vapor deposition of thin films (prepared through, e.g., electron-beam or thermal evaporation), in which the material vapor flux arrives at the substrate surface at an oblique angle. Tilted and columnar nanostructures are the most typical morphological characteristics of OAD thin films. 1, Deposition of ITO films on soda lime glass and silicon substrates was conducted with an E-beam evaporation system using an ITO source composed of 90 wt. % In 2 O 3 and 10 wt. % SnO 2 . Prior to the deposition, all substrates were sequentially cleaned in acetone, isopropyl alcohol, and deionized water and dried under nitrogen flow. The apparatus used in our OAD process has a sample stage (onto which the substrate was loaded), allowing for control of the polarangle as well as azimuthal rotation. The distance between the substrate and evaporation source material was approximately 50 cm. The sample stage was positioned at a fixed polar angle so that the substrate had a certain tilt angle (deposition angle) with respect to the vapor-flux direction. The chamber was evacuated to a pressure less than 1.0 Â 10 À6 Torr, and substrates were held at room temperature. During the deposition, the deposition rate was held steady at 0.2 nm/s, as measured by a quartz crystal monitor inside the chamber. The low growth rate on the substrate at higher deposition angles 11 was compensated by increasing the deposition time to keep the same film thickness for all samples. The ITO films unloaded from the E-beam evaporation system were annealed in O 2 at 550 C for 1 min in a rapid thermal annealing system in order to compensate a deficiency of oxygen in the films. Optical transmittance measurements of the ITO thin films were performed using non-polarized light at normal incidence in the wavelength range of 280-780 nm using a JASCO UV-VIS spectrophotometer. The refractive index (n) was measured using a spectroscopic ellipsometry system, in which absorption is neglected during fitting. A film thickness was measured first by ellipsometry, and then confirmed by a scanning electron microscope (SEM, Hitachi S-4300). The porosity and optical bandgap energy values of the ITO thin films were calculated using theoretical models developed by Poxson et al. 11 and Tauc, 13 respectively. The morphological features of the films were examined using an optical microscope and SEM. Several regions on the sample surface were investigated in order to produce representative images. Furthermore, the crystallographic structure of the ITO thin films was examined by X-ray diffraction (XRD) using the nickel-filtered Ka emission of copper. Figures 1(a) and 1(b) show optical microscope images of the ITO films deposited on (a) silicon (Si) and (b) glass substrates at tilt angles ranging from 0 to 60 . A color difference of the ITO thin films is clearly evident, which can result from a variation in thickness and/or refractive index. In this case, because the thicknesses of all films are the same (about 210 nm), the variation in refractive index is the cause for the color variation. It is well known that the refractive index of a a

Size-dependent fracture in elastomers: experiments and continuum modeling

Elastomeric materials display a complicated set of stretchability and fracture properties that strongly depend on the flaw size, which has long been of interest to engineers and materials scientists. Here, we combine experiments and numerical simulations for a comprehensive understanding of the nonlocal, size-dependent features of fracture in elastomers. We show the size-dependent fracture behavior is quantitatively described through a nonlocal continuum model. The key ingredient of the nonlocal model is the use of an intrinsic length scale associated with a finite fracture process zone, which is inferred from experiments. Of particular importance, our experimental and theoretical approach passes the critical set of capturing key aspects of the size-dependent fracture in elastomers. Applications to a wide range of synthetic elastomers that exhibit moderate (~100%) to extreme stretchability (~1000%) are presented, which is also used to demonstrate the applicability of our approach in elastomeric specimens with complex geometries