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