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HL: Fachverband Halbleiterphysik

HL 27: Nitrides: Preparation and characterization II

HL 27.3: Vortrag

Mittwoch, 14. März 2018, 10:00–10:15, EW 203

Impact of Growth Interruption on the Structure and Luminescence of two- and zero-dimensional GaN/AlN Heterostructures — •Hannes Schürmann, Gordon Schmidt, Sebastian Metzner, Peter Veit, Frank Bertram, Christoph Berger, Jürgen Bläsing, Armin Dadgar, André Strittmatter, and Jürgen Christen — Institute of Experimental Physics, Otto-von- Guericke-University Magdeburg, 39106 Magdeburg, Germany

A systematic series of GaN/AlN quantum dot samples of different growth interruption (GRI) times after GaN deposition has been comprehensively investigated using scanning transmission electron microscopy (STEM) as well as cathodoluminescence (CL) spectroscopy directly performed in a STEM at LHe-temperatures. The sample set was grown by metal organic vapor phase epitaxy on an AlN/sapphire template. Few monolayers (ML) of GaN were grown on top of the smooth AlN surface with a dislocation density of ∼3x10¹⁰ cm^-2. Before capping with 100 nm AlN the GaN surface was exposed only to hydrogen carrier gas for different durations (0 s to 60 s). STEM-CL images of the sample without GRI exhibit hexagonally-shaped GaN islands of 20 nm height and ∼100 nm width located at dislocation bundles, which show no luminescence, and a continuous ∼1.8 nm thin GaN film with an intense emission band between 250 nm and 360 nm wavelength. With increasing growth interruption time, split up, smaller islands indicate desorption processes during the GRI. This GaN island emission now dominates, emitting in the range of 260 to 330 nm and the CL of the 1-2 ML thin GaN film is blue shifted (210 nm).