Unveiling the Hidden Stroke Threat in Patients With Atrial Fibrillation and Primary Hyperparathyroidism.

Recent American College of Cardiology (ACC), American Heart Association (AHA), American College of Clinical Pharmacy (ACCP), and Heart Rhythm Society (HRS) guidelines suggest that patients with atrial fibrillation (AF) at intermediate to low annual risk of ischemic stroke can benefit from consideration of factors that might modify their risk of stroke. The role of nontraditional risk factors, such as primary hyperparathyroidism (PHPT), remains unexplored. In our study, we investigated the potential association between PHPT and the risk of ischemic stroke in patients with AF. Using data from the Nationwide Inpatient Sample Database, a retrospective cohort study focused on the adult population with AF, we stratified the participants based on PHPT presence. Demographic information, co-morbidities, and hospitalization details were extracted using International Classification of Diseases, Tenth revision codes. Propensity score matching was applied, encompassing over 20 confounding variables, including the risk factors outlined in the CHA2DS2-VASc (Congestive heart failure (C), Hypertension (H), Age ≥75 years (A2), Diabetes Mellitus (D), Stroke/Transient Ischemic Attack (TIA)/Thromboembolism (S2), Vascular disease (V), Age 65-74 years (A), Sex category [female] (Sc)) score. Multivariate logistic regression analysis was performed after matching to assess the independent impact of PHPT as an ischemic stroke risk factor. A total of 2,051 of the identified 395,249 patients with AF had PHPT. The PHPT group had an average age of 74 years and consisted of more women (66.1% vs 53.0%). After matching, it was observed that the PHPT group had longer hospital stays (5 vs 4 days) and higher hospitalization charges ($45,126 vs $36,644). This group exhibited higher rates of ischemic stroke (6.0% vs 4.4%) and mortality (6.3% vs 4.9%). The adjusted outcomes showed a 1.4-fold increased risk for ischemic stroke and a 1.32-fold increased risk for mortality in the PHPT cohort. The subgroup analysis showed a higher incidence of mortality in men with a high CHA2DS2-VASc score. In conclusion, this study highlights a marked association between PHPT and ischemic stroke in patients with AF, independent of the conventional CHA2DS2-VASc score. The potential mechanisms implicated include vascular changes, cardiac dysfunction, and coagulation cascade alterations. The presence of PHPT should be taken into consideration when deciding the assessment of thromboembolic risk.

Cost-effectiveness of postoperative imaging surveillance strategies for nonfunctional pituitary adenomas after resection with curative intent.

OBJECTIVE: The aim of this study was to determine an optimal follow-up imaging surveillance strategy in terms of cost-effectiveness after resection of nonfunctioning pituitary adenomas with curative intent. METHODS: An individual-level state-transition microsimulation model was used to simulate costs and outcomes associated with three postoperative imaging strategies over a lifetime time horizon: 1) annual MRI surveillance, 2) tapered MRI surveillance (annual surveillance for 5 years followed by surveillance every 2 years), and 3) personalized surveillance (annual surveillance for 5 years followed by surveillance every 2 years when MRI shows remnant disease/postoperative changes, and surveillance at 7, 10, and 15 years for disease-free MRI). Transition probabilities, utilities, and costs were estimated from recent published data and discounted by 3% annually. Model outcomes included lifetime costs (2022 US dollars), quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs). RESULTS: Under base case assumptions, annual surveillance yielded higher costs and lower health effects (QALYs) compared with the tapered and personalized surveillance strategies (dominated). Personalized surveillance demonstrated an additional 0.1 QALY at additional cost ($1298) compared with tapered surveillance (7.7 QALYs at a cost of $12,862). The ICER was $11,793/QALY. The optimal decision was most sensitive to the probability of postoperative changes on MRI after surgery and MRI cost. Accounting for parameter uncertainty, personalized surveillance had a higher probability of being a cost-effective surveillance option compared with the alternative strategies at 79%. CONCLUSIONS: Using standard cost-effectiveness thresholds in the US ($100,000/QALY), personalized surveillance that accounted for remnant disease or postoperative changes on MRI was cost-effective compared with alternative surveillance strategies.

Risk of Nephrolithiasis in Patients with Inflammatory Bowel Disease Receiving Biologic Treatment.

INTRODUCTION: Inflammatory bowel disease is a chronic inflammatory disorder of the gastrointestinal tract. Biologic drugs target specific molecules in the body's immune system to control inflammation. Recent studies have suggested a potential link between their use and an increased risk of nephrolithiasis. We conducted a study to further investigate this association. METHODS: The study used multiple logistic regression analysis to assess the association between the use of biologic drugs and nephrolithiasis. A p-value of <0.05 was considered statistically significant. SAS 9.4 was used for statistical analysis. RESULTS: The final sample consisted of 22,895 cases, among which 5603 (24.51%) were receiving at least one biologic drug. The biologic drugs received were as follows: Adalimumab 2437 (10.66%), Infliximab 1996 (8.73%), Vedolizumab 1397 (6.11%), Ustekinumab 1304 (5.70%); Tofacitinib, 308 (1.35%); Certolizumab, 248 (1.08%); and Golimumab, 121 (0.53%). There were 1780 (7.74%) patients with Nephrolithiasis: 438 (8.0%) patients were receiving biologic treatment. We found that the use of Vedolizumab (OR = 1.307, 95% CI 1.076-1.588, p = 0.0071) increased the odds of Nephrolithiasis by 31%. CONCLUSION: Vedolizumab use was associated with an increased risk of nephrolithiasis. The use of two or more biologic drugs also increased the risk compared to no biologic treatment.

Manual neuronavigation for superior semicircular canal dehiscence surgery.

Background: Intraoperative identification of a superior semicircular canal (SSC) dehiscence via the middle cranial fossa approach (MCFA) remains a difficult endeavor without a neuronavigation system. To address these challenges, we propose a technique to localize the SSC dehiscence intraoperatively using certain anatomical landmarks. Method: Three anatomical landmarks should be identified on preoperative radiological images: the distance from the squamous part of the temporal bone to the dehiscent SSC, the lower limit of the craniotomy, and the exact location of the craniotomy in relation to the bony external auditory canal. The use of these landmarks intraoperatively can allow the surgeon to correctly identify the position of the SSC. Two instructional videos explaining this technique are presented. Conclusion: The proposed manual neuronavigation technique seems to be an accurate, safe, and cost-effective alternative technique for use in SSC dehiscence surgery.

Preoperative evaluation of depth of invasion in oral tongue squamous cell carcinoma: A systematic review and meta-analysis.

The inclusion of depth of invasion (DOI) in the American Joint Committee on Cancer's staging system for oral cavity squamous cell carcinoma (SCC) has major clinical impacts. Recent studies have evaluated the reliability of imaging modalities and biopsy techniques to measure DOI preoperatively. The objective of this systematic review and meta-analysis was to comprehensively include all previously described methods to measure preoperative DOI in oral tongue SCC (OTSCC) and to compare their reliability. A systematic review was conducted on PubMed, Embase and Cochrane according to the PRISMA guidelines. Studies that evaluated the reliability of DOI measured on biopsy or imaging (rDOI) by comparing it to DOI on histopathology (pDOI) were included for extraction. A meta-analysis was conducted to obtain pooled correlation coefficients for each imaging modality. The pooled correlation coefficients between rDOI and pDOI were 0.86 (CI95% = [0.82-0.88]) and 0.80 (CI95% = [0.70-0.87]) for magnetic resonance imaging (MRI) studies and computed tomography (CT) studies, respectively. For ultrasound (US), the correlation coefficient could only be measured by including studies which measured not only DOI but also tumor thickness. It was 0.89 (CI95%= [0.82-0.94]). Overall, MRI is the better studied modality. It has a good reliability to measure preoperative rDOI in OTSCC. CT is less studied but appears to be less reliable. US cannot be compared to these imaging modality as it has been used more often to measure TT than DOI.

Post-operative surveillance for somatotroph, lactotroph and non-functional pituitary adenomas after curative resection: a systematic review.

CONTEXT: Pituitary tumors are the third most common brain tumor and yet there is no standardization of the surveillance schedule and assessment modalities after transsphenoidal surgery. EVIDENCE ACQUISITION: OVID, EMBASE and the Cochrane Library databases were systematically screened from database inception to March 5, 2020. Inclusion and exclusion criteria were designed to capture studies examining detection of pituitary adenoma recurrence in patients 18 years of age and older following surgical resection with curative intent. EVIDENCE SYNTHESIS: A total of 7936 abstracts were screened, with 812 articles reviewed in full text and 77 meeting inclusion criteria for data extraction. A pooled analysis demonstrated recurrence rates at 1 year, 5 years and 10 years for non-functioning pituitary adenomas (NFPA; N = 3533 participants) were 1%, 17%, and 33%, for prolactin-secreting adenomas (PSPA; N = 1295) were 6%, 21%, and 28%, and for growth-hormone pituitary adenomas (GHPA; N = 1257) were 3%, 8% and 13%, respectively. Rates of recurrence prior to 1 year were 0% for NFPA, 1-2% for PSPA and 0% for GHPA. The mean time to disease recurrence for NFPA, PSPA and GHPA were 4.25, 2.52 and 4.18 years, respectively. CONCLUSIONS: This comprehensive review of the literature quantified the recurrence rates for commonly observed pituitary adenomas after transsphenoidal surgical resection with curative intent. Our findings suggest that surveillance within 1 year may be of low yield. Further clinical trials and cohort studies investigating cost-effectiveness of surveillance schedules and impact on quality of life of patients under surveillance will provide further insight to optimize follow-up.

Inferior Wall ST-Elevation Myocardial Infarction Complicated by Left Ventricular Pseudoaneurysm, Cardiac Tamponade, and Partial Papillary Muscle Rupture.

Papillary muscle rupture (PMR) is a rare complication of myocardial infarction. Its incidence has been decreasing nowadays because of improved early revascularization techniques. When it occurs, surgical treatment is the only therapeutic lifesaving approach. We report a case of an 85-year-old female patient who presented to the emergency room with chest pain. An electrocardiogram showed inferior wall ST-elevation myocardial infarction. The patient was revascularized emergently with a drug-eluting stent to the obtuse marginal artery. An intra-aortic balloon pump was inserted for hemodynamic support. Six hours later, the patient developed shortness of breath with persistent hypotension. A transthoracic echocardiogram (TTE) showed a large pericardial effusion with a pseudoaneurysm in the infero-septal apex. Immediate drainage of pericardial fluid was performed. Seventy-two hours later, the patient had flash pulmonary edema. A new severe eccentric mitral regurgitation was discovered on transesophageal echocardiography (TEE). Findings revealed a partial posteromedial papillary muscle tear and prolapse of the A2 scallop. The patient was not a candidate for surgical replacement or percutaneous repair due to the high surgical risk and poor functional status, and she passed away on day fifteen of her hospital stay. Limited case series have shown promising benefits of percutaneous edge-to-edge mitral valve repair in selected high surgical risk patients and as a bridge to definitive mitral valve replacement. A diagnosis of PMR should be in the differential diagnosis, especially when evaluating hemodynamically unstable patients who present with prolonged symptoms.

Isolated oropharyngeal abscess with hypopharyngeal extension recurring 12 years after initial surgical management: A case report and review of the literature.

Pharyngeal abscesses require urgent management as they have the propensity to cause severe and life-threatening complications. The introduction of antibiotics has led to a dramatic decline in the incidence of these infections. Regardless, abscess formation continues to be observed in the peritonsillar, parapharyngeal, and retropharyngeal spaces. Oropharyngeal and hypopharyngeal abscesses that cause airway obstruction are scarcely reported and tend to be secondary to other processes. Herein, we describe the case of an 83-year-old man presenting with an idiopathic, obstructive, oropharyngeal wall abscess, extending from the infratonsillar region to the hypopharynx, which recurred after initial surgical management 12 years prior for the same process. He required reintervention during both episodes for rapid reaccumulation. A detailed electronic literature search of PubMed and MedLine was performed for studies reporting on recurrent pharyngeal abscesses and their management. Results were limited to articles published in English from inception to August 2021. The timely management of pharyngeal infections acutely obstructing the airway is crucial. Physicians should adopt close and frequent monitoring and have a low threshold for reimaging should symptoms worsen or fail to improve after the initial surgical intervention.

Characteristics of persistent postural perceptual dizziness patients in a multidisciplinary dizziness clinic.

BACKGROUND: Persistent Postural Perceptual Dizziness (PPPD) is a newly defined condition which was added to the International Classification of Vestibular Disorders in 2017. Little is known about its impact on patients. OBJECTIVE: The goal of this study was to analyze the symptomology, epidemiology and impact of PPPD on patients. METHODS: A retrospective chart review was done to identify patients who attended the Multidisciplinary Dizziness Clinic (MDC) and were diagnosed with PPPD. Responses to demographic questions, health-related quality of life surveys and several well-validated questionnaires commonly used to assess dizziness severity were analyzed. RESULTS: One hundred patients were diagnosed with PPPD between March 2017 and January 2019, of which 80%(80/100) were females. The average Dizziness Handicap Index score was 60.3±19.0. Responses to the Patient Health Questionnaire classified 53 patients (53/99;53.5%) as moderately to severely depressed. Sixty-four patients (64/100;64.0%) were minimally or mildly anxious according to the Generalized Anxiety Disorder scale. The average Vertigo Symptom Scale score was 24.1/60. The average Situational Vertigo Questionnaire score was 2.00. Forty-nine (49/100;49.0%) patients had migraine symptoms according to the Migraine Screen Questionnaire. CONCLUSIONS: In conclusion, patients with PPPD display important handicap and an elevated risk of depression, anxiety and migraines.

Current Practice of Percutaneous Coronary Intervention in Patients With Coagulation Disorders.

Acute coronary artery disease represents the leading cause of death worldwide. Some studies have shown that coagulation disorders can play a protective role against ischemic heart disease, presumably due to hypocoagulable state and decrease thrombin formation. However, autopsy reports showed atherosclerotic lesions in some patients with hemophilia. Since the introduction of clotting factors and replacement therapies, the life expectancy of patients with coagulation disorders has increased significantly. As a result, the incidence of cardiovascular diseases became higher making their treatment more challenging. Door to balloon strategy applies in ST-elevation myocardial infarction (STEMI), and percutaneous coronary intervention should not be delayed. While in non-STEMI (NSTEMI) and unstable angina, a hematology consult is essential. Prophylactic coagulation factor replacement is crucial in these patients in order to avoid bleeding complications, but on the other hand, these factors were also associated with thrombotic complications. Historically, bare-metal stents were preferred over drug-eluting stents in view of the shorter duration of dual antiplatelets therapy (DAPT). Currently, some trials have demonstrated the safety of new-generation drug-eluting stents in patients with elevated bleeding risk, where DAPT use is limited to four weeks. The radial artery is the preferred access and was found to have less bleeding complications when compared to the femoral access. Anticoagulation with heparin is the safest in view of antidote availability and shorter half-life. Bivalirudin has also been used in some case reports, while GP2b3a inhibitors are usually avoided except in a high thrombus burden. Close peri procedural follow-up is important with patient education about symptoms of bleed. Carefully and individually tailored antithrombotic and factor replacement therapy is required to overcome these clinically challenging situations. Early screening for cardiovascular risk factors and considering early intervention and management might help to improve the general health status of this population and reduce morbidity.

The Association Between the Syrian Crisis and Cutaneous Leishmaniasis in Lebanon.

INTRODUCTION: Displacement of refugees from highly endemic areas of leishmaniasis to adjacent countries is associated with the spread of Leishmania. Syria is a country with a known high endemicity for cutaneous leishmaniasis and the presence of Syrian refugees in Lebanon has contributed to the re-emergence of the disease. The aim of this article is to evaluate the burden of cutaneous leishmaniasis in Lebanon in view of the presence of a large number of Syrian refugees. METHODS: Data regarding all cases of leishmaniasis were collected from reports by the Lebanese Ministry of Public Health-Epidemiology Surveillance (LMPH-ESU), and the World Health Organization (WHO) between 2005 and 2018. All cases were reviewed in terms of area of residence, age and gender, clinical presentation, treatment, and outcome. An extensive literature review was conducted using "PubMed", "Medline", and "Google Scholar". RESULTS: The annual number of leishmaniasis cases recorded in Lebanon between 2005 and 2011 ranged between 0 and 6 cases. In 2012, this number increased to 1275 cases and dropped to 263 in 2018, where all those infected were Syrian refugees from Aleppo, with zero cases of local transmission. Seventy-two percent of cases were seen in patients aged < 20 years. The predominant species of Leishmania was L. tropica followed by L. major. CONCLUSION: Lebanon was affected by leishmaniasis following the Syrian crisis, and the influx of refugees to the country. Accurate disease monitoring and strategic training of healthcare personnel based within refugee camps are essential for proper containment. Preventative measures remain the best way to avoid both local and adjacent spread of leishmaniasis.

Giant Coronary Artery Aneurysm: A Successful Diagnosis.

Coronary artery aneurysms (CAAs) are rare, with giant CAAs being even rarer. The precise pathophysiology of this phenomenon is still unknown. CAAs are seldom reported life-threatening abnormalities of the cardiovascular system. We herein present a case of a 74-year-old man who presented at the hospital complaining of chest pain. An adenosine thallium scan revealed a small, reversible defect in the inferior wall of the left ventricle extending into the apex, consistent with ischemia. Echocardiography uncovered a large right coronary artery (RCA) aneurysm, measuring 5.6 × 7.5 cm. Diagnostic coronary angiography confirmed the presence of a large RCA aneurysm and aneurysmal dilation of the left anterior descending and circumflex arteries with no flow-limiting lesions. A reversed saphenous vein interposition graft was placed from the ascending aorta to the right posterior descending artery. The RCA aneurysmal sac was resected and sent to pathology, which uncovered myxoid degeneration of the media as well as thrombus formation. No complications were encountered during the procedure. Early diagnosis is vital to avoid fatal complications of CAAs, and therapeutic approaches are currently individualized in view of absence of evidence-based management strategies.

More than Just Soup: Use of a Student-Led COVID-19 Social Pediatrics Initiative to Propose the Integration of Social Medicine Electives in Undergraduate Medical Education.

INTRODUCTION: The need to educate medical students on the social forces shaping disease and health patterns is paramount in preparing incoming physicians with the aptitudes to address health inequities. Despite its well-documented merit as a model of practice, social medicine remains underrepresented at the undergraduate medical education level. We hypothesize that the success of this student-led COVID-19 initiative proposes a tangible and innovative solution to address the lack of social medicine exposure in undergraduate medical education. METHODOLOGY: We sought to evaluate the impact of sustaining clinical learning during the pandemic using the social pediatrics model as a didactic vector for clerkship students. We extracted learning objectives relevant to the teaching of social medicine from the Royal College of Physicians and Surgeons of Canada's CanMEDS framework and developed a survey aimed at evaluating the attainability of each of those objectives. The survey was distributed to students enrolled in the social pediatrics COVID-19 initiative after 6 weeks (April-May), as well as a control group. RESULTS: Completing the survey were 19 students from the University of Ottawa Faculty of Medicine, 7 in the intervention group and 12 in the control group. Students that participated in the social pediatrics initiative yielded significantly higher values for the achievement of 6 out of 9 social medicine learning objectives when compared to the control group. Although the values followed a similar trend for the remaining 3 objectives, favoring the intervention group, they were not statistically significant. CONCLUSION: The positive results from this study and the COVID-19 student-led initiative template can serve as a catalyst for curricular change so as to ensure graduates are adequately trained to contend with the realities of the social landscape in which they will practice. Future plans include the incorporation of interactive social medicine experiences throughout all 4 years of medical school.

Preclerkship Point-of-Care Ultrasound: Image Acquisition and Clinical Transferability.

INTRODUCTION: The integration of point-of-care ultrasound (POCUS) in preclerkship medical education is currently popular and based on the notion that POCUS may improve diagnostic and procedural skills in medical students. However, empirical evidence demonstrating that POCUS can enhance clinical skills in preclerkship students has been lacking. We sought to evaluate anatomical sonographic knowledge and ultrasound generation capabilities associated with the implementation of a 3-h echocardiography training camp led by 2 emergency physicians and using a flipped classroom design. METHODS: Preclerkship students from the University of Ottawa (n = 32) were recruited to participate. A flipped classroom model was adopted, providing students with a 3-chaptered peer-designed, expert validated ultrasound manual before the workshop, to maximize scanning times (2 h of reading). A pretest Likert-type design was used to assess student perception of the ultrasound tool. Similarly, a pretest/post-test model was used to assess sonographic anatomical identification. In addition, a subsequent Objective Structured Clinical Examination (OSCE) test was done 3 weeks after the hands-on session, to evaluate image generation (4 cardiac views: parasternal long, parasternal short, subxiphoid, and apical 4 chambers), understanding of knobology and structural labeling. RESULTS: For the sonographic anatomy, there was a statistically significant increase (P < .001) between pretest (average = 12.12) and post-test (average = 18.85). The OSCE, which also ascertained knowledge retention, found that 81% of students were able to generate all 4 cardiac views perfectly, 6% were able to obtain 3 views, 10% obtained 2 views and 3% successfully generated a single view. The most challenging scan to generate was the apical 4-chamber view. CONCLUSION: The positive outcomes stemming from this study reinforces the notion that formal curricular integration of POCUS at the preclerkship level has tangible benefits for medical students.

Citation impact was highly variable for reporting guidelines of health research: a citation analysis.

OBJECTIVES: Over 400 reporting guidelines are currently published, but the frequency of their use by authors to accurately and transparently report research remains unclear. This study examined citation counts of reporting guidelines and characteristics contributing to their citation impact. STUDY DESIGN AND SETTING: Web of Science database was searched for citation counts of all reporting guidelines with a minimum citation age of 5 years. The total citation impact, mean citation impact and the factors contributing to 2- and 5-year citation rate were established. RESULTS: The search identified 296 articles of reporting guidelines from 1995 to 2013. The mean citations per year was 32.4 (95% confidence interval, 22.3-42.4 citations). The factors associated with 2- and 5-year citation performance of reporting guidelines included the following: open access to the reporting guideline, field of the publishing journal (general vs. specialized medical journal), impact factor of the publishing journal, simultaneous publication in multiple journals, and a male first author. CONCLUSION: The citation rate across reporting guidelines varied with journal impact factor, open access publication, field of the publishing journal, simultaneous publications, and a male first author. Gaps in citations highlight opportunities to increase visibility and encourage author use of reporting guidelines.

560†nm InGaN micro-LEDs on low-defect-density and scalable (20-21) semipolar GaN on patterned sapphire substrates.

We demonstrate InGaN-based semipolar 560 nm micro-light-emitting diodes with 2.5% EQE on high-quality and low-defect-density (20-21) GaN templates grown on scalable and low-cost sapphire substrates. Through transmission electron microscopy observations, we discuss how the management of misfit dislocations and their confinement in areas away from the active light-emitting region is necessary for improving device performance. We also discuss how the patterning of semipolar GaN on sapphire influences material properties in terms of surface roughness and undesired faceting in addition to indium segregation at the proximity of defected areas.

Reporting guidelines of health research studies are frequently used inappropriately.

OBJECTIVES: Appropriate use of reporting guidelines of health research ensures that articles present readers with a consistent representation of study relevance, methodology, and results. This study evaluated the use of major reporting guidelines. STUDY DESIGN AND SETTING: A cross-sectional analysis of health research articles citing four major reporting guidelines indexed in the Web of Science Core Collection (up to June 24, 2018). Two independent reviews were performed in a random sample of 200 articles, including clinical trials (N = 50), economic evaluations (N = 50), systematic reviews (N = 50), and animal research studies (N = 50). The use of reporting guidelines to guide the reporting of research studies was considered appropriate. Inappropriate uses included the use of the reporting guidelines as a tool to assess the methodological quality of studies or as a guideline on how to design and conduct the studies. RESULTS: Across all selected reporting guidelines, appropriate use of reporting guidelines was observed in only 39% (95% CI: 32-46%; 78/200) of articles. By contrast, inappropriate use was observed in 41% (95% CI: 34-48%; 82/200), and unclear/other use was observed in 20% (95% CI: 15-26%; 40/200). CONCLUSIONS: Reporting guidelines of health research studies are frequently used inappropriately. Authors may require further education around appropriate use of the reporting guidelines in research reporting.

Demonstration of Electrically Injected Semipolar Laser Diodes Grown on Low-Cost and Scalable Sapphire Substrates.

The last two decades have shown an increasing need for GaN-based laser diodes (LDs), which are currently only grown on bulk GaN substrates, which remain to date very expensive and/or only available in small sizes. The ever growing laser market will expand in the coming years, thanks to the development of automotive laser lighting, high-speed Li-Fi optical data transmission, LiDAR sensing for autonomous vehicles and smart cities, head-up displays, and AR/VR systems, in addition to biomedical and further industrial applications. These emerging technologies demand for mass-production of GaN-based lasers to be produced on large-size, low-cost, and industrially compatible substrates. To address this issue, we demonstrate the first electrically injected semipolar 440 nm LD on high-quality and low-defect-density (11-22) GaN templates grown on scalable and low-cost sapphire substrates. The LDs exhibit a threshold current density of 17 kA/cm2, a single facet output power of more than 200 mW at 2 A with a slope efficiency of 0.85 W/A, and a TE polarization having a ratio of 97.6%. These results enable the advancement of ultra-low-cost LDs while benefiting from the inherent advantages of semipolar GaN properties.

Study of efficient semipolar (11-22) InGaN green micro-light-emitting diodes on high-quality (11-22) GaN/sapphire template.

We investigated the electrical and optical performances of semipolar (11-22) InGaN green µLEDs with a size ranging from 20 × 20 µm2 to 100 × 100 µm2, grown on a low defect density and large area (11-22) GaN template on patterned sapphire substrate. Atom probe tomography (APT) gave insights on quantum wells (QWs) thickness and indium composition and indicated that no indium clusters were observed in the QWs. The µLEDs showed a small wavelength blueshift of 5 nm, as the current density increased from 5 to 90 A/cm2 and exhibited a size-independent EQE of 2% by sidewall passivation using atomic-layer deposition, followed by an extremely low leakage current of ~0.1 nA at -5 V. Moreover, optical polarization behavior with a polarization ratio of 40% was observed. This work demonstrated long-wavelength µLEDs fabricated on semipolar GaN grown on foreign substrate, which are applicable for a variety of display applications at a low cost.