Microstructure and growth morphology as related to electro-optical properties of heteroepitaxial wurtzite GaN on sapphire (0001) substrates

Autor: Giancarlo Salviati, Karl Joachim Ebeling, M Mayer, A Pelzmann, Markus Kamp, W. Dorsch, Martin Albrecht, Horst P. Strunk, Silke Christiansen, C. Zanotti-Fregonara
Rok vydání: 1997
Předmět:
Zdroj: Materials Science and Engineering: B. 43:296-302
ISSN: 0921-5107
DOI: 10.1016/s0921-5107(96)01879-x
Popis: We investigate the microstructural development during growth and the related electro-optical properties of gallium nitride (GaN) films deposited on (0001) sapphire substrates by gas source molecular beam epitaxy. We use transmission electron microscopy, atomic force microscopy, scanning tunnelling microscopy, spectrally resolved cathodoluminescence (CL) mapping and photoluminescence (PL). We report on specimens exhibiting UV luminescence (band-to-band transition at 358 nm/3.46 eV) in CL/PL and an additional strong yellow luminescence (Gaussian shaped CL peaks at around 528 nm/2.35 eV). The specimens show a surface topology with facetted hexagonal islands with a width of 1–2 μm at a height of 50 nm. A correlation with spectrally resolved CL images shows: the yellow luminescence is homogeneously distributed over the whole of the specimens as are the pure screw dislocations with b→=〈0001〉, while the UV luminescence is confined to troughs between adjacent hexagonal islands where edge type dislocations with b→=1/3〈2¯110〉) or b→=1/3〈21¯1¯3〉) form small angle boundaries. These dislocations do favour or at least do not impair UV luminescence. Formation mechanisms for the different defect types and possibilities for their reduction are briefly considered.
Databáze: OpenAIRE
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