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HL: Fachverband Halbleiterphysik

HL 8: Nitrides: Devices

HL 8.4: Vortrag

Montag, 16. März 2020, 10:15–10:30, POT 51

Effects of degradation on the electrooptical properties of UVB-LEDs measured by temperature dependent electroluminescence spectroscopy — •Jakob Höpfner¹, Priti Gupta¹, Martin Guttmann¹, Jan Ruschel², Johannes Glaab², Tim Kolbe², Arne Knauer², Tim Wernicke¹, Markus Weyers², and Michael Kneissl^1,2 — ¹Technische Universität Berlin, Institute of Solid State Physics, Berlin, Germany — ²FBH, Berlin, Germany

The operation of UVB-LEDs induces changes in their electrooptical behaviour, especially a reduction in the emission power. As the lifetime of a device is a key property for its application, it is important to understand the processes governing their degradation behavior. We report an investigation on UVB-LEDs emitting at 310 nm before and after aging (1000 h at 100 mA (67 A cm⁻²) and heatsink temperature of 70 ^∘C) using temperature(T)–dependent electroluminescence spectroscopy from 20 K – 340 K. Before aging, the external quantum efficiency (EQE) at 10 mA gradually increases with decreasing temperature from 0.8 % at 340 K to 1.8 % at 150 K and then levels off. This is similar to the expected change in radiative recombination efficiency (η_rad) with decreasing temperature due to the reduction of the non-radiative recombinations, indicating that EQE(T) is dominated by η_rad. After aging, the EQE reduces to 0.45 % (340 K) and the EQE(T) shows a constant increase with decreasing temperature peaking at 1.4 % (80 K). Below 80 K, a sharp droop in EQE is observed in the case of aged LED. These findings indicate a reduction in both η_rad and injection efficiency as degradation mechanism in aged LEDs.