Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 31: Poster: Nitrides

HL 31.7: Poster

Montag, 31. März 2014, 17:00–20:00, P2

RF-MBE growth of AlN on sapphire utilizing AlN nucleation layers — •Christopher Hein, Andreas Kraus, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institute of Applied Physics, TU-Braunschweig, Germany

AlN is a promising material for laser as well as quantum well structures due to its high thermal conductivity and stability as well as large bandgap. Further AlN can be used to grow self assembled GaN quantum dots. We report on our AlN growth on sapphire with a Riber 32P RF-MBE. Experiments cover the investigation of the influence of nucleation layers. Before growth a nitridation step at a temperature of 200^∘C was performed. AlN nucleation layers were grown at 400^∘C. 500 nm thick epilayers were grown at 700^∘C using either continuous or metal modulated epitaxy. Growth rates were 3.4 nm/min with a III/V ratio of ∼ 1. AFM micrographs of samples with increasing nucleation layer thickness show a decreasing RMS roughness down to 0.7 nm. Strikingly a narrow peak in symmetric XRD omega scans was observed, whose FWHM was resolution limited. The appearance of the narrow peak is also seen in MOVPE grown AlN on sapphire for layer thicknesses below 1-2 µm. It is assumed to originate from an interference effect of small crystallites highly ordered in c-direction. This assumption can be confirmed by our experiments with increasing AlN nucleation layer thicknesses giving rise to smaller grains as seen by AFM. Relating this to the results from omega scans, the intensity of the narrow peak decreases with increasing nucleation layer thickness, hinting at a correlation between grain size and the interference.