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DF: Fachverband Dielektrische Festkörper

DF 26: Metamorphic structures: Bringing together incompatible materials I (Joint Focus Session with HL and DS)

DF 26.10: Vortrag

Donnerstag, 3. April 2014, 12:45–13:00, POT 251

Metamorphic growth of UV-B LEDs on Al_0.5Ga_0.5N on AlN/Sapphire by MOVPE — •Johannes Enslin¹, Frank Mehnke¹, Martin Guttmann¹, Christoph Reich¹, Jens Rass^1,2, Tim Wernicke¹, and Michael Kneissl^1,2 — ¹Technische Univerät Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany

For AlGaN-based LEDs emitting in the UV-B spectral region between 280 nm and 320 nm relaxed buffer layers enable pseudomorphic growth of the multiple quantum well active region. In our contribution we present a study of the effects of various superlattice designs on pseudomorphic growth. The superlattice consists of 80 periods of AlN and GaN layers. We found that the thickness of the GaN layer and the relative AlN to GaN layer thicknesses (i.e. AlN/GaN ratio) are crucial for the relaxation process. 4.5 µm thick Al_0.5Ga_0.5N with an AlN/GaN ratio of one exhibits high densities of pits and cracks. LEDs grown on this layer show no luminescence most likely due to these defects. UV-B LEDs grown on templates with AlN/GaN ratios ≤ 0.4 exhibit fewer pits and no cracks, but show only poor luminescence. A smooth morphology was obtained for GaN thicknesses ≤ 2 nm and AlN/GaN ratios between 0.4 and 0.8. XRD scans show a distinct superlattice reflection. Reduced densities of pits and cracks indicate metamorphic growth. The optical emission power obtained from 305 nm LEDs grown on those layers reaches values up to 2.3 mW at 60 mA.