Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC

The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes (LEDs) is limited due to their poor light extraction efficiency (LEE). To improve the LEE of AlGaN LEDs, we developed a fabrication technology to process AlGaN LEDs grown on SiC into thin-film flip-chip LEDs (TFFC LEDs) with high LEE. This process transfers the AlGaN LED epi onto a new substrate by wafer-to-wafer bonding, and by removing the absorbing SiC substrate with a highly selective SF6 plasma etch that stops at the AlN buffer layer. We optimized the inductively coupled plasma (ICP) SF6 etch parameters to develop a substrate-removal process with high reliability and precise epitaxial control, without creating micromasking defects or degrading the health of the plasma etching system. The SiC etch rate by SF6 plasma was ~46 \mu m/hr at a high RF bias (400 W), and ~7 \mu m/hr at a low RF bias (49 W) with very high etch selectivity between SiC and AlN. The high SF6 etch selectivity between SiC and AlN was essential for removing the SiC substrate and exposing a pristine, smooth AlN surface. We demonstrated the epi-transfer process by fabricating high light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To further enhance the light extraction, the exposed N-face AlN was anisotropically etched in dilute KOH. The LEE of the AlGaN LED improved by ~3X after KOH roughening at room temperature. This AlGaN TFFC LED process establishes a viable path to high external quantum efficiency (EQE) and power conversion efficiency (PCE) UV-C LEDs.Comment: 22 pages, 6 figures. (accepted in Semiconductor Science and Technology, SST-105156.R1 2018

Growth of highly conductive Al-rich AlGaN:Si with low group-III vacancy concentration

Publisher Copyright: © 2021 Author(s).The impact of AlGaN growth conditions on AlGaN:Si resistivity and surface morphology has been investigated using metalorganic chemical vapor deposition. Growth parameters including growth temperature, growth rate, and trimethylindium (TMI) flow have been systematically studied to minimize the resistivity of AlGaN:Si. We observed a strong anticorrelation between AlGaN:Si conductivity and growth temperature, suggesting increased silicon donor compensation at elevated temperatures. Secondary ion mass spectrometry and positron annihilation spectroscopy ruled out compensation by common impurities or group-III monovacancies as a reason for the observed phenomenon, in contrast to theoretical predictions. The underlying reason for AlGaN:Si resistivity dependence on growth temperature is discussed based on the possibility of silicon acting as a DX center in Al0.65Ga0.35N at high growth temperatures. We also show remarkable enhancement of AlGaN:Si conductivity by introducing TMI flow during growth. A minimum resistivity of 7.5 m? cm was obtained for n-type Al0.65Ga0.35N, which is among the lowest reported resistivity for this composition.& nbsp;(c)& nbsp;2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).& nbsp;Peer reviewe

Prevalence of Hepatitis C Viral Infection among Diabetes Mellitus Patients in Qassim Region, Saudi Arabia

The worldwide prevalence of Diabetes Mellitus (DM) associated with Hepatitis C Virus (HCV) infection are reported with higher rates of morbidity and mortality. The frequency of HCV is approximately 3-4 million cases each year and in parallel the incidence of DM is increasing alarmingly. World Health Organization (WHO) has specified that DM will be the 7th leading cause of mortality by 2030. The increasing association between HCV and DM has been indicated by some significant reports recently. HCV infection leads to hepatic steatosis and rapid insulin resistance, which in turn upsurges the risk factors for hepatic fibrosis and hepatocellular carcinoma. This study is designed to examine the association between HCV and DM, and different risk factors associated with HCV infection in Qassim region, Kingdom of Saudi Arabia (KSA). A total of 634 blood samples were obtained from diabetic and non-diabetic patients. These blood samples were first screened for HCV infection by enzyme-linked immunosorbent assay (ELISA) and positive samples were again confirmed by TaqMan HCV quantitative test and the viral load in different samples was estimated. The HCV prevalence was identified as 2.5% in diabetic patients with a positive association between HCV and DM (RR= 1.24, OR= 1.77) which is not significant statistically. However, the HCV prevalence among diabetic females was significantly different from males (p<0.05). The behavioural factors had no significant impact to acquire HCV infection. This study indicated a positive association between HCV and DM. Gender was an association factor in the HCV and DM status. Further studies with larger sample size is significant to properly assess the temporal relationship between HCV and DM

AlGaN growth and processing for high-efficiency UV LED on SiC

AlGaN is among the ultra-wide band gap semiconductors that are projected to power a wide range of the next-generation electronic and photonic applications. It has been applied primarily for the development of germicidal UV LEDs that are crucial for virus disinfection and gained an extra importance in the era of COVID-19 pandemic, with proven efficacy against wide range of viruses - including SARS-CoV-2 - that rivals the most mature disinfection technologies. However, state-of-the-art deep UV LEDs are still lagging behind visible LEDs in terms of output power, lifetime and cost. Our approach to tackle this issue relies on silicon carbide as a growth substrate in contrast to sapphire. Firstly, The advantages gained by employing SiC as a substrate will be highlighted. Secondly, growth of Al-rich AlGaN on SiC by Metalorganics chemical vapor deposition (MOCVD) will be the main focus of this thesis, with emphasis on the AlGaN growth kinetics, doping and active region, Detailing simple, yet robust, solutions for AlGaN cracking, doping inefficiency and multiquantum wells (MQW) growth—solutions that enabled the growth of up to 5 micron-thick crack-free AlGaN films on SiC (among the highest reported), and the growth of highly conductive Al-rich n-AlGaN films up to 83% Al molar fraction with conductivities that match and exceed the best reported in the literature, as well as the growth of MQW with tunable and monochromatic emission in the UV range of maximal disinfection efficacy (250 nm to 280 nm).. In Al-rich AlGaN, the increased ionic character of Al-N bond leads to dissimilar kinetical behavior between Al and Ga adatoms, as well as precipitates several key challenging issues such as greater deviation from ideal unit cell structure, anisotropic light emission and inefficient doping. This work tackles these limits and explores growth and processing techniques to address these challenges, specifically; optimization of n-doped AlGaN will be illustrated with focus on the effect of the different growth parameters on the conductivity and ohmic contact formation. Studies on the impact of MOCVD growth conditions on the UV LEDs performance will be presented, emphasizing how the growth outcome can be influenced by other external parameters; starting from chamber geometry and conditioning to substrate polishing, preparation and pretreatment. Then, the device performance of UVC led will be summarized along with new solutions to further improve the overall performance

Emotional stability and its relationship to anxiety about coronavirus among Najran University students

The study aimed to examine the relationship between emotional stability and anxiety about Coronavirus among Najran University students. To achieve the objectives of this descriptive study, the researchers used the scales of emotional stability and anxiety about the Coronavirus pandemic.&nbsp; The study sample consisted of (521) students at Najran University (319 males, 202 females), who were selected following the simple random method. The results revealed that the students’ level of emotional stability came to a medium degree, and the level of anxiety about the Coronavirus pandemic among students also came to a medium degree. In addition, there was a negative statistically significant correlation between emotional stability and the level of anxiety about the Coronavirus. The study revealed statistically significant differences in the level of emotional stability according to the gender variable in favor of females, indicating that males were more emotionally stable than females. Furthermore, there were significant differences based on the type of college in favor of scientific colleges. However, no significant differences in the level of anxiety in favor of gender or college type

6-Gingerol, a Bioactive Compound of Ginger Attenuates Renal Damage in Streptozotocin-Induced Diabetic Rats by Regulating the Oxidative Stress and Inflammation

The aim of present study is to investigate the role of 6-gingerol in ameliorating the renal injury in streptozotocin (STZ)-induced diabetic rats. The diabetes was induced by using a single dose of freshly prepared STZ (55 mg/kg body weight) intraperitoneally which causes the degeneration of pancreatic Langerhans islet β-cells. The diabetic rats were treated with oral gavage of 6-gingerol (10 mg/kg b.w.). The treatment plan was continued for 8 weeks successively and the body weight and fasting blood glucose levels were weekly checked. The biochemical parameters like lipid profile, kidney profile, antioxidant enzyme levels, lipid peroxidation and anti-inflammatory marker levels were investigated after the treatment plant. The pathological condition of kidneys was examined by haematoxylin-eosin (H&E) staining besides this analysis of NF-κB protein expression by immuno-histochemistry was performed. Some of the major parameters in diabetes control vs. normal control were reported as fasting blood glucose (234 ± 10 vs. 102 ± 8 mg/dL), serum creatinine (109.7 ± 7.2 vs. 78.9 ± 4.5 μmol/L) and urea (39.9 ± 1.8 vs. 18.6 mg/dL), lipid profile levels were significantly enhanced in diabetic rats. Moreover, diabetic rats were marked with decreased antioxidant enzyme levels and increased inflammatory markers. Treatment with 6-gingerol significantly restored the fasting blood glucose level, hyperlipidaemia, Malondialdehyde (MDA) and inflammatory marker levels, NF-κB protein expression and augmented the antioxidant enzyme levels in the kidneys of diabetic rats. The kidney damage was significantly normalized by the treatment of 6-gingerol and it provides an evidence that this novel compound plays a significant role in the protection of kidney damage. These findings demonstrate that 6-gingerol reduces lipid parameters, inflammation and oxidative stress in diabetic rats, thereby inhibiting the renal damage. Our results demonstrate that use of 6-gingerol could be a novel therapeutic approach to prevent the kidney damage associated with the diabetes mellitus

6-Gingerol, a Bioactive Compound of Ginger Attenuates Renal Damage in Streptozotocin-Induced Diabetic Rats by Regulating the Oxidative Stress and Inflammation

The aim of present study is to investigate the role of 6-gingerol in ameliorating the renal injury in streptozotocin (STZ)-induced diabetic rats. The diabetes was induced by using a single dose of freshly prepared STZ (55 mg/kg body weight) intraperitoneally which causes the degeneration of pancreatic Langerhans islet β-cells. The diabetic rats were treated with oral gavage of 6-gingerol (10 mg/kg b.w.). The treatment plan was continued for 8 weeks successively and the body weight and fasting blood glucose levels were weekly checked. The biochemical parameters like lipid profile, kidney profile, antioxidant enzyme levels, lipid peroxidation and anti-inflammatory marker levels were investigated after the treatment plant. The pathological condition of kidneys was examined by haematoxylin-eosin (H&amp;E) staining besides this analysis of NF-κB protein expression by immuno-histochemistry was performed. Some of the major parameters in diabetes control vs. normal control were reported as fasting blood glucose (234 ± 10 vs. 102 ± 8 mg/dL), serum creatinine (109.7 ± 7.2 vs. 78.9 ± 4.5 μmol/L) and urea (39.9 ± 1.8 vs. 18.6 mg/dL), lipid profile levels were significantly enhanced in diabetic rats. Moreover, diabetic rats were marked with decreased antioxidant enzyme levels and increased inflammatory markers. Treatment with 6-gingerol significantly restored the fasting blood glucose level, hyperlipidaemia, Malondialdehyde (MDA) and inflammatory marker levels, NF-κB protein expression and augmented the antioxidant enzyme levels in the kidneys of diabetic rats. The kidney damage was significantly normalized by the treatment of 6-gingerol and it provides an evidence that this novel compound plays a significant role in the protection of kidney damage. These findings demonstrate that 6-gingerol reduces lipid parameters, inflammation and oxidative stress in diabetic rats, thereby inhibiting the renal damage. Our results demonstrate that use of 6-gingerol could be a novel therapeutic approach to prevent the kidney damage associated with the diabetes mellitus

Effect of Fibres on Physico-Mechanical Properties of Bulk-Fill Resin Composites

Objective: To measure the flexural strength (FS) of bulk-fill resin composites and assess their long-term water absorption and solubility properties with and without the inclusion of short glass fibres. Methods: One resin composite, everX Flow with fibres, and four commercially available bulk-fill composites without fibres, namely, PALFIQUE, Activa, SDR Plus, and Filtek Bulk Fill One, were tested. Six specimens (2 × 2 × 25 mm) were fabricated for each material and stored in water for 1 day and 30 days to measure the flexural strength using a three-point bending test. To evaluate water absorption and solubility, circular disks measuring 15 × 2 mm (n = 5) were immersed in water for 60 days, and their weights were recorded periodically. After 60 days, the specimens were dried for an additional 21 days to determine solubility. Results: Flexural strength values ranged from 101.7 to 149.1 MPa. Significant distinctions were observed among the resin composites at the onset of the study (p p p 3. ACT also had the highest solubility, whereas everX Flow exhibited negative solubility. Significance: The addition of short fibres, along with potential differences in matrix composition, enhanced the flexural strength of everX Flow. However, the substantial reduction in flexural strength observed in everX Flow and SDR following exposure to water corroborates the manufacturers’ recommendation to apply a conventional resin composite cap on these materials