Characterization of an AlN buffer layer and a thick-GaN layer grown on sapphire substrate by MOCVD

Date
2010-10-23
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Source Title
Journal of Materials Science
Print ISSN
0022-2461
Electronic ISSN
Publisher
Springer
Volume
46
Issue
6
Pages
1606 - 1612
Language
English
Type
Article
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Abstract

An AlN buffer layer and a thick-GaN layer for high-electron-mobility transistors (HEMTs) were grown on sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The structural and morphological properties of the layers were investigated by high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) techniques. The optical quality of the thick-GaN layer was also evaluated in detail by a photoluminescence (PL) measurement. It was found that the AlN buffer layer possesses high crystal quality and an atomically flat surface with a root-mean-square (rms) roughness of 0.16 nm. The screw-and edge-type dislocation densities of the thick-GaN layer were determined as 5.4 9 107 and 5.0 9 109 cm-2 by means of the mosaic crystal model, respectively. It was observed that the GaN layer has a smooth surface with an rms of 0.84 nm. Furthermore, the dark spot density of the GaN surface was estimated as 6.5 9 108 cm-2 over a scan area of 4 μm2. © Springer Science+Business Media, LLC 2010.

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Keywords
Atomically flat surface, Crystal qualities, Dark spots, Dislocation densities, GaN layers, High-resolution x-ray diffraction, Mosaic crystal model, Optical qualities, Photoluminescence measurements, Root mean square roughness
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Published Version (Please cite this version)