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26 February 2016 Influence of the LED heterostructure on the degradation behavior of (InAlGa)N-based UV-B LEDs
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Abstract
In this paper we report on the influence of the heterostructure design of (InAlGa)N-based UV-B LEDs grown by metalorganic vapor phase epitaxy on sapphire substrates on the degradation behavior of the device. Two types of LEDs with different heterostructure design, resulting in peak-wavelengths of about 290 nm and 310 nm, respectively, were stressed at a constant operation current of 100 mA and a heat sink temperature of 20°C. Electro-optical characterization of the LEDs over 1.000 h of operation shows two different degradation modes with respect to the change of the emission spectrum and leakage current. The first mode during the initial hours (290 nm LED: 0 h - 500 h, 310 nm LED: 0 h – 100 h) of operation is represented by a fast reduction of the quantum well (QW) luminescence, a constant or increasing parasitic luminescence between 310 nm and 450 nm and a fast increase of the reverse- and forward-bias leakage current. These changes are more pronounced (higher degradation rate) in the 290 nm LEDs and can therefore be attributed to the different heterostructure design. In contrast, the second degradation mode at longer operation times (290 nm LED: >500 h, 310 nm LED: >100 h) is marked by a slow reduction of both the QW and the parasitic luminescence, as well as a slow increase of the leakage current which are similar for both types of LEDs. Furthermore, the second mode is marked by a square-root time dependence of the QW luminescence intensity, indicating a diffusion process to be involved.
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Johannes Glaab, Neysha Lobo Ploch, Jens Rass, Tim Kolbe, Tim Wernicke, Frank Mehnke, Christian Kuhn, Johannes Enslin, Christoph Stölmacker, Viola Kueller, Arne Knauer, Sven Einfeldt, Markus Weyers, and Michael Kneissl "Influence of the LED heterostructure on the degradation behavior of (InAlGa)N-based UV-B LEDs", Proc. SPIE 9748, Gallium Nitride Materials and Devices XI, 97481O (26 February 2016); https://doi.org/10.1117/12.2208906
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