Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 46: Focus Session: AlGaN Materials for UV Emitters
HL 46.3: Topical Talk
Mittwoch, 28. März 2012, 10:30–11:00, ER 164
High-efficiency AlGaN-based light-emitting diodes for the UV-A wavelength range — •Richard Gutt1, Thorsten Passow1, Michael Kunzer1, Wilfried Pletschen1, Lutz Kirste1, Kamran Forghani2, Ferdinand Scholz2, Klaus Köhler1, and Joachim Wagner1 — 1Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Freiburg — 2Institut für Optoelektronik, Universität Ulm
To date, AlGaN-based light emitting diodes (LEDs) emitting in the ultraviolet (UV) wavelength range exhibit much lower external quantum efficiencies (EQE) compared to their highly-developed GaN-based counterparts covering the visible spectral range. This can be ascribed to two major reasons. On the one hand, epitaxial growth of AlGaN on sapphire typically leads to a large density of threading dislocations, which are known to act as non-radiative recombination centers. On the other hand, the demand for shorter emission wavelengths inhibits the use of GaInN quantum wells (QWs), which show efficient light emission despite the quite high dislocation density in GaN-based LEDs.
In this talk, we present different approaches towards the reduction of threading dislocations in AlGaN with an Al content of ∼ 20 %. Moreover, a significant enhancement in light emission by using GaN QWs with very low In content is demonstrated. We also address the challenges in achieving a high carrier injection and light extraction efficiency. Combining all these measures, we demonstrated LEDs emitting at wavelengths around 350 nm with an EQE exceeding 7 %, which is among the highest values reported for AlGaN-based LEDs.