Degradation of (In)AlGaN-Based UVB LEDs and Migration of Hydrogen

J. Glaab1, J. Ruschel1, T. Kolbe1, A. Knauer1, J. Rass1, H.K. Cho1, N. Lobo Ploch1, S. Kreutzmann1, S. Einfeldt1, M. Weyers1, and M. Kneissl1,2

Published in:

IEEE Photonics Technol. Lett., vol. 31, no. 7, pp. 529-532 (2019).

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Abstract:

We report on the degradation of the electro-optical parameters of (In)AlGaN-based ultraviolet-B light-emitting diodes (LEDs) stressed at a constant dc current of 100 mA and the simultaneous change in the depth profile of the hydrogen (H) concentration during operation. The optical power of the LEDs decreased to ∼45% of its initial value after 10 h of operation and saturated for longer operation times. In addition, the drive voltage dropped in about the first 10 h of operation and gradually increased in the following operation time. The possible changes in the impurity distribution in the LEDs during operation have been studied by means of secondary-ion-mass spectrometry of the magnesium (Mg) and the H depth profiles after 10 and 100 h of operation. We could not resolve any significant change in the Mg profile. In contrast, after 10 h of operation, the H concentration in the electron-blocking layer (EBL), p-side, and active region significantly reduced, and the H formed two concentration peaks close to the active region and deeper in the n-side. After 100 h, the H concentration in the EBL and p-side did not change, but the H in the n-side propagated further away from the pn junction. A degradation mechanism is proposed, which includes the breaking of atomic bonds of the H-containing defect complexes and the migration of H atoms during operation.

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany
2 Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany

Index Terms:

InAlGaN, light-emitting diode (LED), UV-B, degradation, defect migration.