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HL: Fachverband Halbleiterphysik

HL 25: Poster: Nitrides

HL 25.14: Poster

Montag, 20. März 2017, 15:00–19:00, P2-OG2

Conoscopic Investigation of Birefringence in GaN Samples — •Lukas Uhlig, Ines Trenkmann, Matthias Wachs, and Ulrich T. Schwarz — Chemnitz University of Technology, Experimental Sensor Science, Reichenhainer Str. 70, 09126 Chemnitz, Germany

The propagation of light through GaN layers is influenced by birefringence. That means the refractive indices of the ordinary and extraordinary rays are different and depend in the case of the extraordinary one on the angle between the extraordinary ray and the c-axis. Superposition of these both rays leads to a change of the state of polarization compared to the initial ray. This effect can be observed well using the introduced conoscopic experimental setup, where the sample is located between a polarizer and an analyzer, that is rotated by 90^∘. For uniaxial crystals, like GaN, with the c-axis orientate parallel to the optical axis the observed conoscopic images show concentric rings and a dark "maltese" cross in the middle, wich is called isogyre. We describe a method for the evaluation of the resulting conoscopic pattern and compare these with simulated images using refractive indices Δ n=n_e−n_o from various studies [1-3].

References: [1] S. Shokhovets, R. Goldhahn and W. Richter, J. Appl. Phys. 94, 307 (2003). [2] G. Yu, H. Ishikawa and M. Umeno, Jpn. J. Appl. Phys. 36, L1029 (1997). [3] S. Ghosh, P. Waltereit and K. H. Ploog, Appl. Phys. Lett. 80, 413 (2002).