Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 35: HL Poster II
HL 35.15: Poster
Mittwoch, 3. April 2019, 17:30–20:00, Poster E
Optical polarization of AlGaN multiple quantum wells emitting between 212 nm and 261 nm — •Bettina Belde1, Fynn Wolf1, Frank Mehnke1, Martin Guttmann1, Christoph Reich1, Luca Sulmoni1, Tim Wernicke1, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin
The output power and external quantum efficiency of AlGaN based LEDs is dropping rapidly for emission wavelengths below 240 nm. This can partly be explained by the transition of the optical polarization from transverse electric (TE) to transverse magnetic (TM) which is determined by the valence band ordering and symmetry in multiple quantum wells (MQW) that depend strongly on the aluminum content.
Using photoluminescence (PL), the optical polarization of the emitted light of AlGaN MQW has been investigated at room temperature in dependence of the aluminum content in the QWs and the barriers. The polarization degree P=(TE-TM)/(TE+TM) for 1 nm AlxGa1−xN / AlyGa1−xN QWs changes from +0.85 (TE) for x=0.48 and y=0.61 to -0.58 (TM) for x=0.9 and y=100. The transition from TE to TM occurs at an emission wavelength of 238 nm in good agreement with simulations based on k· p-perturbation theory. Furthermore, the investigation of the polarization degree was confirmed by polarization resolved electroluminescence (EL) measurements of processed LEDs with similiar active regions.