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標題: Influences of temperature ramping rate on GaN buffer layers and subsequent GaN overlayers grown by metalorganic chemical vapor deposition
作者: Wuu, D.S.
Horng, R.H.
Tseng, W.H.
Lin, W.T.
Kung, C.Y.
關鍵字: GaN;buffer layer;temperature ramping rate;MOCVD;X-ray;AFM;sapphire substrate surface;nucleation layers;photoluminescence;nitridation;films;movpe
Project: Journal of Crystal Growth
期刊/報告no:: Journal of Crystal Growth, Volume 220, Issue 3, Page(s) 235-242.
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 low-temperature-deposited GaN buffer layer annealed under various ramping rates (20-60 degreesC/min) to 1000 degreesC were investigated by atomic force microscopy and X-ray measurements. For lower ramping rates employed, a dramatic re-evaporation of the GaN buffer layer might occur. This makes the buffer layer thinner, yielding a GaN epilayer of hexagonal morphology. However, as the higher ramping rates are 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 do not have enough time to coarsen. Under a temperature ramping rate of 40 degreesC/min, a smooth buffer-layer surface can be maintained and results in a subsequent high-quality overlayer deposition. The mirror GaN epilayer shows a near-band-edge peak (25 K) centered at 3.477eV with a full-width at half-maximum as narrow as 13.1meV. The observed temperature-ramping-rate effects can be interpreted by the coalescence mechanism of the GaN buffer layer. (C) 2000 Elsevier Science B.V. All rights reserved.
ISSN: 0022-0248
DOI: 10.1016/s0022-0248(00)00821-6
Appears in Collections:材料科學與工程學系

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