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We developed a new buffer layer to grow GaN epilayers with a low dislcoation density by metalorganic chemical vapor deposition (MOCVD). The buffer layer consists of a 20 nm GaNP layer deposited at low temperature (500 °C) on sapphire substrate using phosphine (PH3) as phosphorus source. With optimalized PH3 flow rate, the quality of the GaNP buffer GaN epilayer is improved, demonstrated by X-ray diffraction, transmission electron miscroscopy, atomic force microscopy, and cathodoluminescence. The dislocation density in the GaN buffer GaN epilayer is decreased to as low as 5 × 108 cm−2 from 1–5 × 109 cm−2 in a conventional GaN epilayer. The dislocation reduction mechanism were discussed by investigating the growth evolution beginning from the GaNP buffer. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) |
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