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Impact of operation parameters on the degradation of 233 nm AlGaN-based far-UVC LEDs

J. Glaab1, J. Ruschel1, N. Lobo Ploch1, H.K. Cho1, F. Mehnke2,b, L. Sulmoni2, M. Guttmann2, T. Wernicke2, M. Weyers1, S. Einfeldt1, and M. Kneissl1,2

Published in:

J. Appl. Phys., vol. 131, no. 01, pp. 014501, doi:10.1063/5.0069590 (2022).

Abstract:

The impact of the operation parameters current and temperature on the degradation of AlGaN-based 233 nm far-ultraviolet-C LEDs is investigated. The observed effects can be divided into two groups: First, a rapid reduction in the optical power to about 50%-30% of the initial value during the first ∼100 h of operation, which is accompanied by an increase in the current below the diffusion voltage from 0.3 to about 1 µA, and a reduction in the hydrogen concentration in the p-side close to the active region. The second group is represented by a gradual reduction of the optical power, which runs in parallel to the effects in the first group and dominates for operation times ≥100 h. The reduction of the optical power is due to a decrease in the slope of the optical power-current characteristic. All effects are accelerated at increased stress currents and current densities - the reduction in the optical power at low (∼20 mA) and high measuring current (∼80 mA) scales with the current to the power of three. For example, after 250 h of operation, the relative optical power at a measuring current of 20 mA has decreased to about 40% when the LED was operated at a stress current of 20 mA and to <10% for a stress current of 100 mA. Furthermore, temperature has no significant impact on the reduction of the optical power during operation, i.e., the relative optical power reduced to about 25% after 250 h both when the LEDs were operated at 20°C and when they were operated at 75°C.

1 Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
2 Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin, Germany
b Present address: School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive, Atlanta, GA 30332

Topics:

Crystallographic defects, Ultraviolet light, Optical properties, Semiconductors, Electrical properties and parameters, Light emitting diodes, Recombination reactions

Copyright © 2022 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). https://doi.org/10.1063/5.0069590

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