Japanese Journal of Applied Physics, 2013, Vol.52(8S)
We have decreased the dislocation density in Al x Ga 1- x N epitaxial layers grown on sapphire wafers by introducing an in-situ deposited SiN nano-mask layer. Taking together results obtained by transmission electron microscopy, photoluminescence, cathodoluminescence, and X-ray diffraction, we were able to derive a schematic model about the AlGaN growth on the SiN nanomask: On the open pores of the nano-mask, Ga-rich AlGaN hillocks develop, whereas on the SiN layer Al-rich AlGaN nucleates owing to the reduced selectivity of Al-containing material. Once the hillocks are formed, Ga-rich material is more efficiently incorporated on the inclined side-facets leading to an Al-rich coverage of the central c -plane part of the hillocks. We observed a bending of the dislocations towards the side-facets of the hillocks, which eventually leads to dislocation bundles with increased probability of dislocation annihilation, separated by fairly defect-free regions. Thus, we could achieve a significant reduction of the edge-type dislocation density in these epitaxial layers.
Aluminum Gallium Nitrides ; Reduction ; Bundles ; Dislocations ; Epitaxial Layers ; Aluminum ; Dislocation Density ; Nanostructure ; Materials Selection ; Defects and Transport (Wc) ; Applied Physics (General) (So) ; Microstructure (EC) ; Constitution/Crystal Structure/Microstructure (AI) ; Physics (General) (Ah);
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