Degradation of (In)AlGaN-Based UVB LEDs and Migration of Hydrogen
IEEE Photonics Technol. Lett., vol. 31, no. 7, pp. 529-532 (2019).
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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
InAlGaN, light-emitting diode (LED), UV-B, degradation, defect migration.