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Proceedings Paper

Initial growth effects on the properties of GaN buffer layer and subsequent GaN overlayer by MOCVD
Author(s): DongSing Wuu; WeiHao Tseng; WeiTsung Lin; RayHua Horng
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Paper Abstract

The role of temperature ramping rate during the two-step growth of GaN-on-sapphire by metalorganic chemical vapor deposition is explored. The surface morphology and crystalline properties of the GaN buffer layer annealed under various temperature ramping rates (20-60 degree(s)C/min) were investigated by atomic force microscopy and x-ray measurements. For the lower ramping rates employed, a dramatic re-evaporation of the GaN buffer layer was observed. This makes the buffer layer thinner, yielding the GaN epilayer of hexagonal morphology. However, as the higher ramping rates applied, the surface becomes rougher and exhibits hexagonal three-dimensional islands. It could be due to the fact that the grains of the GaN buffer layer have no enough time to course. Under a temperature ramping rate of 40 degree(s)C/min, a smooth buffer-layer surface can be maintained and result in a subsequent high-quality over- layer deposition. The mirror GaN epilayer shows a near-band- edge peak (25 K) centered at 3.477 eV with a full width at half maximum as narrow as 13.1 meV. The observed temperature-ramping-rate effects can be interpreted by the coalescence mechanism of the GaN buffer layer involving Ostwald ripening, sintering and cluster migration.

Paper Details

Date Published: 11 July 2000
PDF: 7 pages
Proc. SPIE 4078, Optoelectronic Materials and Devices II, (11 July 2000); doi: 10.1117/12.392109
Show Author Affiliations
DongSing Wuu, Da-Yeh Univ. (Taiwan)
WeiHao Tseng, Da-Yeh Univ. (Taiwan)
WeiTsung Lin, Da-Yeh Univ. (Taiwan)
RayHua Horng, National Chung Hsing Univ. (Taiwan)

Published in SPIE Proceedings Vol. 4078:
Optoelectronic Materials and Devices II
Yan-Kuin Su; Pallab Bhattacharya, Editor(s)

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