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Martin-Luther-University
Interdisziplinäres Zentrum für Materialwissenschaften
Nanotechnikum Weinberg
Heinrich-Damerow-Str. 4,
D-06120 Halle, Germany
Phone: +49 345 55 28471
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Ada Wille, Benjamin Reuters, Matthias Finken, Frank Heyroth, Georg Schmidt, Michael Heuken, Holger Kalisch, Andrei Vescan
Strain relief mechanisms and growth behavior of superlattice distributed Bragg reflectors
phys. stat. sol. C 11 (2014), 758-761

In this work, the successful use of AlN/GaN superlattices (SL) as the low-index lambda/4 layer of distributed Bragg reflectors (DBR) is demonstrated. DBR samples were grown with MOVPE on 2 inch sapphire substrates and a standard GaN buffer structure. The samples were characterized using high-resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and white-light reflectometry. With this concept, effective Al contents of 30% in the low-index layers of the DBR can be realized without the occurrence of layer cracking or relaxation. This is attributed to a staircase propagation of the TD in the DBR structure. By kinking into the in-plane direction, the TD is able to relieve in-plane strain on a micro-scale. In this way, relaxation or cracking of the whole layer can be prohibited. A study of growth rate optimization was performed. As a result, the growth rate of the DBR was increased maintaining the high interface quality and optical performance.

Keywords: distributed Bragg reflector; MOVPE; dislocation staircase pattern; crack-free

DOI10.1002/pssc.201300444


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