Local current measurements for avalanche breakdown in Silicon p-n junctions

Application of Photon Emission Microscopy (PEM) in semiconductor characterization often shows a linear dependence between emission intensity and biasing current. However, inconclusive understanding of photon emission phenomena in Silicon stopped the research community form applying PEM for local current estimation. In this paper we show for the first time that the linear relationship is valid for avalanche breakdown in the range of currents across five orders of magnitude. And we conclude that the observed relationship is independent of non-radiative effects. Using the observed photon emission pattern we perform a detailed analysis of the influence of the junction geometry and doping topology on the breakdown phenomenon. We also for the first time estimate the local I-V curves in the junction and demonstrate the complexity of the breakdown phenomenon. Our results also demonstrate a poor applicability of global I-V curve measurements for calibration of existing TCAD models

Cardiovascular magnetic resonance imaging and spectroscopy in clinical long-COVID-19 syndrome: a prospective case–control study

Background The underlying pathophysiology of post-coronavirus disease 2019 (long-COVID-19) syndrome remains unknown, but increased cardiometabolic demand and state of mitochondrial dysfunction have emerged as candidate mechanisms. Cardiovascular magnetic resonance (CMR) provides insight into pathophysiological mechanisms underlying cardiovascular disease and 31-phosphorus CMR spectroscopy (31P-CMRS) allows non-invasive assessment of the myocardial energetic state. The main aim of the study was to assess whether long COVID-19 syndrome is associated with abnormalities of myocardial structure, function, perfusion and energy metabolism. Methods Prospective case–control study. A total of 20 patients with a clinical diagnosis of long COVID-19 syndrome (seropositive) and no prior underlying cardiovascular disease (CVD) and 10 matching healthy controls underwent 31P-CMRS and CMR at 3T at a single time point. All patients had been symptomatic with acute COVID-19, but none required hospital admission. Results Between the long COVID-19 syndrome patients and matched contemporary healthy controls there were no differences in myocardial energetics (phosphocreatine to ATP ratio), in cardiac structure (biventricular volumes), function (biventricular ejection fractions, global longitudinal strain), tissue characterization (T1 mapping and late gadolinium enhancement) or perfusion (myocardial rest and stress blood flow, myocardial perfusion reserve). One patient with long COVID-19 syndrome showed subepicardial hyperenhancement on late gadolinium enhancement imaging compatible with prior myocarditis, but no accompanying abnormality in cardiac size, function, perfusion, extracellular volume fraction, native T1, T2 or cardiac energetics. Conclusions In this prospective case–control study, the overwhelming majority of patients with a clinical long COVID-19 syndrome with no prior CVD did not exhibit any abnormalities in myocardial energetics, structure, function, blood flow or tissue characteristics