Micro Epitaxial lateral overgrowth of GaN/sapphire by Metal Organic Vapour Phase Epitaxy
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Internet Journal Nitride Semiconductor Research
Micro Epitaxial lateral overgrowth of GaN/sapphire by Metal Organic Vapour Phase Epitaxy E. Frayssinet1, B. Beaumont1, J. P. Faurie1, Pierre GIBART1, Zs. Makkai2, B. Pécz2, P. Lefebvre3 and P. Valvin3 1Lumilog,
2720, Chemin de Saint Bernard, Les Moulins I, 06220 Vallauris, FRANCE, Institute for Technical Physics and Matl. Sci., H-1525 Budapest, POBox 49, 3Groupe d'Etude des Semiconducteurs, GES-CNRS, 2Research
(Received Tuesday, November 5, 2002; accepted Monday, December 9, 2002)
GaN/sapphire layers have been grown by Metal Organic Vapour Phase Epitaxy (MOVPE). An amorphous silicon nitride layer is deposited using a SiH4/NH3 mixture prior to the growth of the low temperature GaN buffer layer. Such a process induces a 3D nucleation at the early beginning of the growth, resulting in a kind of maskless ELO process with random opening sizes. This produces a significant decrease of the threading dislocation (TD) density compared to the best GaN/sapphire templates. Ultra Low Dislocation density (ULD) GaN layers were obtained with TD density as low as 7×107cm-2 as measured by atomic force microscopy (AFM), cathodoluminescence and transmission electron microscopy (TEM). Time-resolved photoluminescence experiments show that the lifetime of the A free exciton is principally limited by capture onto residual donors, similar to the situation for nearly dislocation-free homoepitaxial layers.
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Introduction
The III-V compound semiconductor family has proven high performance in high-speed electronics, optical emitters, (i.e. laser diodes (LDs) and light emitting diodes (LEDs)) and detectors. However, for efficient operation, high crystalline quality is required. Growth technologies for large-scale substrates are currently very advanced for Si (and to a lesser extent, GaAs) and less advanced for InP and other III-V substrates. For GaN, bulk crystals are not readily available. Bulk GaN is intrinsically very difficult to grow because of the high vapour pressure of nitrogen at the melting point of GaN. GaN single crystals (about 1 cm2) are, however, produced by high temperature and high-pressure growth, mainly at UNIPRESS (Poland). [1] Even though these crystals are very valuable for basic physics and demonstration of ultimate performance of devices, their size and potential production volume do not come close to meeting industrial needs. Since there is no GaN bulk single crystal available, the entire technological development of GaN based devices relies on heteroepitaxy. GaN is currently grown epitaxially by MOVPE, Halide Vapour Phase Epitaxy (HVPE) and Molecular Beam Epitaxy (MBE). Most of
the current device structures are grown on sapphire or 6H-SiC. Potentially more appropriate substrates like LiAlO2, MgAl2O4, ScMgAlO4, 6H-SiC, ZnO and Hf have been tested in several laboratories. [2] Even though good quality GaN epilayers have been obtained, none have been significantly better than GaN/ sapphire layers. The use of alternative substrates has therefore not yet solved the probl
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