Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 46: Nitrides: mostly structural characterization

HL 46.1: Talk

Tuesday, April 1, 2014, 11:45–12:00, POT 051

Aberration-corrected STEM investigation of epitaxial GaN thin films — •David Poppitz, Andriy Lotnyk, Jürgen W. Gerlach, and Bernd Rauschenbach — Leibniz-Institut für Oberflächenmodifizierung e. V., Permoserstr. 15, D-04318 Leipzig

The semiconductor material GaN is widely used in photonics applications. To improve emission efficiency it is necessary to minimize density of defects in GaN thin films. In this study epitaxial GaN thin films with different thicknesses and a high crystalline quality were produced by ion-beam assisted molecular-beam epitaxy (IBA-MBE) on 6H-SiC substrates. These thin films were characterized by advanced transmission electron microscopy at the atomic scale. A FEI Titan G2 60-300 probe aberration corrected scanning transmission electron microscope (S/TEM) was used to perform the experiments. Annular bright field (ABF) STEM imaging was applied for imaging of carbon and nitrogen elements at the GaN-SiC interface. To identify strain in the thin films nano-beam diffraction (NBD) experiments were done.

High-resolution STEM investigations showed a high density of defects in regions close to the GaN-SiC interface. The defects were identified as grain and antiphase boundaries, stacking faults as well as dislocations at the boundaries. It was also found that the thin films consist of hexagonal and cubic GaN. ABF-STEM studies of the GaN-SiC interface revealed local polarity of GaN structure at the interface as Ga-polar. Above a certain thickness, the thin films grow as hexagonal GaN and with highly reduced defect densities.