Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: Nitrides: Preparation and Characterization

HL 50.9: Talk

Wednesday, March 22, 2017, 12:15–12:30, POT 251

Conoscopic study: Influence of birefringence on the state of polarization in GaN samples — •Ines Trenkmann, Lukas Uhlig, Matthias Wachs, and Ulrich T. Schwarz — Chemnitz University of Technology, Experimental Sensor Science, Reichenhainer Str. 70, 09126 Chemnitz, Germany

GaN with its wurtzite crystal structure is an optical anisotropic material. In a conoscopic setup, the birefringent sample is placed between two crossed polarizers and the state of polarization of the emerging beam is compared to the polarization of the initial ray. Fringes and the typical black bands of the isogyre characterize the obtained conoscopic interference pattern, which depend on the sample thickness, the cone of the incident light ray and the difference between both refractive indices Δ n=n_e−n_o . We compare experimental obtained pattern with simulated images using refractive indices from various studies that are obtained by variable angle spectroscopic ellipsometry [1, 2] and prism coupling technique [3]. The observed differences are discussed considering growth induced crystal strain. Additionally measurements of epitaxial GaN on sapphire show the influence of the sapphire substrate on the observed changes of the state of polarization [4].

References: [1] S. Shokhovets, R. Goldhahn and W. Richter, J. Appl. Phys. 94, 307 (2003). [2] S. Ghosh, P. Waltereit and K. H. Ploog, Appl. Phys. Lett. 80, 413 (2002). [3] G. Yu, H. Ishikawa and M. Umeno, Jpn. J. Appl. Phys. 36, L1029 (1997). [4] I. Trenkmann, L. Uhlig, M. Wachs, C. Mounir, U. T. Schwarz, submitted.