Regensburg 2019 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 35: HL Poster II
HL 35.13: Poster
Wednesday, April 3, 2019, 17:30–20:00, Poster E
Temperature-dependent electroluminescence studies of AlGaN-based UVB-LEDs — •Jakob Höpfner1, Priti Gupta1, Martin Guttmann1, Markus Weyers2, Tim Wernicke1, and Michael Kneissel1,2 — 1Technische Universität Berlin, Institut of Solid State Physics, Berlin, Germany — 2Ferdinand Braun Institut, Berlin, Germany
One of the important contributors to the external quantum efficiency (EQE) and output power of the AlGaN-based deep UV-LEDs is the injection efficiency (ηinj). It is mainly determined by electron overflow into the p-doped region and the restricted hole Transport into the quantum wells due to a high acceptor activation energy and band offsets at heterointerfaces. By measuring the temperature (T)-dependent electroluminescence (EL) characteristics of UVB-LEDs, we can provide insights on hole and electron transport in these LEDs. From the T (20-350 K)-dependent EL specta, current-voltage and current-light output power characteristics, we observed the typical behavior of UVB-LEDs. Starting at 350 K, the EQE first increases with decreasing T due to the reduced non-radiative recombination rate within the quantum wells. At a certain T, the EQE decreases strongly staying at low values for lower T. The origin of the EQE breakdown is possibly the freeze out of holes in conjunction with increased electron overflow. Our results show that the temperature, at which EQE reaches its maximum, depends strongly on the ηinj, which can be pushed to even lower temperature with improved p-doping and bandgap profile.