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HL: Fachverband Halbleiterphysik

HL 25: Poster: Nitrides

HL 25.16: Poster

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

Determination of threading dislocation density of AlN on sapphire substrates by X-ray diffraction — •Daniel Pacak¹, Johannes Enslin¹, Tim Wernicke¹, Sylvia Hagedorn², Arne Knauer², Carsten Hartmann³, Heike Oppermann³, Markus Weyers², and Michael Kneissl^1,2 — ¹Technische Universität Berlin, Institute of Solid State Physics — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik — ³Leibniz-Institut für Kristallzüchtung, Berlin

AlN on sapphire substrates with low threading dislocation density (TDD) is essential for the growth of efficient UV light emitting diodes. The TDDs of a series of AlN layers on sapphire with different dislocation densities, ranging from 1·10⁹cm⁻² to 2·10¹⁰cm⁻² were determined by X-ray diffraction (XRD) by measuring the FWHM of ω-scans for different reflections. For this, we first separated the broadening of the XRD peaks due to finite coherent length and wafer curvature from the broadening by tilt and twist. Then the tilt and twist contributions were determined by two different approaches. One method was based on obtaining the tilt value by measuring a reflection in asymmetric geometry and calculating the corresponding twist value. In a second approach the tilt and twist components were determined by extrapolating the FWHM against the χ-angle. From these tilt and twist values we calculated the TDDs for correlated and randomly distributed dislocations, based on the models of Chierchia et al. and Dunn & Kogh. Finally we compared the TDD obtained by XRD with the results from defect selective etching.