196,209 research outputs found
Lifetime Prediction of Current-and Temperature-Induced Degradation in Silicone-Encapsulated 365 nm High-Power Light-Emitting Diodes
No full textWe report on the degradation mechanisms and dynamics of silicone encapsulated ultraviolet A (UV-A) high-power light-emitting diodes (LEDs), with a peak wavelength of 365nm. The stress tests were carried out for a period of 8665 hours with forward currents between 350mA and 700mA and junction temperatures up to 132°C. Depending on stress condition, a significant decrease in optical power could be observed, being accelerated with higher operating conditions. Devices stressed at a case temperature of 55 °C indicate a decrease in radiant flux between 10-40% varying with measurement current, whereas samples stressed at higher case temperatures exhibit crack formation in the silicone encapsulant accompanied by electromigration shorting the active region. The analyzed current and temperature dependency of the degradation mechanisms allows to propose a degradation model to determine the device lifetime at different operating parameters. Additional stress test data collected at different aging conditions is used to validate the model's lifetime predictions.</p
Impact of thermal annealing on deep levels in nitrogen-implanted β-Ga2O3Schottky barrier diodes
No full textUnderstanding the properties of N-implanted β-Ga2O3 is fundamental for the optimization of doping and isolation structures based on gallium oxide. This paper reports an extensive analysis of the impact of thermal annealing on the concentration and properties of deep levels in N-implanted β-Ga2O3 Schottky barrier diodes by means of capacitance isothermal transient spectroscopy. Samples with annealing temperatures from 800 to 1200 °C were considered. The original results presented in this paper demonstrate the following: (a) The instability of current-voltage characteristics detected for all the samples under test can be attributed to the presence of three electron traps with activation energies of 0.6, 0.7, and 1 eV, consistent with previous reports in β-Ga2O3. (b) The detected traps are not the nitrogen level but intrinsic defects whose concentration is increased by the implantation process. (c) The concentration of deep levels decreases as the annealing temperature increases, demonstrating that the annealing process can effectively restore the quality of the material while keeping the conductivity decrease related to the presence of the nitrogen. Finally, (d) we demonstrate that the residual leakage and the turn-on voltage shift are correlated with the Arrhenius signature of the detected deep levels. An interpretation is proposed to explain the measurement results
Modeling of the Conduction Processes and Deep Levels in Annealed Nitrogen-Implanted β-Gallium Oxide Schottky diodes
No full textFailure limits and electro-optical characteristics of GaN-based LEDs under electrical overstress
No full textDr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Understanding the degradation processes of GaN based LEDs submitted to extremely high current density
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Degradation mechanisms in high power InGaN semiconductor lasers investigated by electrical, optical, spectral and C-DLTS measurements
No full textThe aim of this work is to study the degradation processes in high power InGaN semiconductor lasers, by means of electrical, optical, spectral and capacitance deep-level transient spectroscopy measurements. The devices were submitted to two different stress experiments, (i) a constant current stress at 1.5 A and 45 °C, and (ii) a temperature/bias step stress at 1 A and increasing temperature. Results demonstrated: (i) two different mechanisms that change the drive voltage, one due to the activation of Mg and one ascribed to the generation of point defects; (ii) a parasitic peak is present in the emission spectra, ascribed to the recombination in a second quantum well (QW); (iii) redistribution of charge takes place during the temperature step stress
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