Effects of Growth Temperatures on Crystal Quality of GaN by Vapor Phase Epitaxy Using GaCl3 and NH3
Thick epitaxial growth of GaN by vapor phase epitaxy (VPE) is an indispensable technique to form GaN substrates which have been commonly used for blue-violet GaN-based lasers with sufficiently long lifetime. Although the growth has been established in view of the mass-production of the GaN substrate...
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| Published in | Jpn J Appl Phys Vol. 50; no. 8; pp. 085501 - 085501-5 |
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| Main Authors | , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
01.08.2011
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| Online Access | Get full text |
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| Summary: | Thick epitaxial growth of GaN by vapor phase epitaxy (VPE) is an indispensable technique to form GaN substrates which have been commonly used for blue-violet GaN-based lasers with sufficiently long lifetime. Although the growth has been established in view of the mass-production of the GaN substrate, the crystal quality has never been sufficiently correlated with the growth conditions. In this paper, the effects of the growth temperatures on the crystal quality of VPE-grown GaN films are studied in detail. It is noted that the GaN films are grown by a single-zone VPE using externally placed GaCl 3 and NH 3 as source precursors. The growth exhibits the growth rate of 14 μm/h at highest and far higher growth rate is possible by increasing the carrier flow rate and/or temperature of the GaCl 3 . The experimental results reveal that the surface morphology and optical properties are strongly dependent on the growth temperature. At around 975 °C with very narrow temperature window, very smooth surface together with a very sharp photoluminescence (PL) peak originating from bound excitons is observed. Growth at lower temperatures than the optimized window results in rough surface with many pits on it. Higher temperature results in many cracks and peeling-off on the surface with the sign of three-dimensional growth. Peaks originating from residual acceptors are dominant in the PL spectra of the films with rough surfaces grown at higher or lower temperatures from the optimized window. Flattening the surface of GaN at the optimized temperatures by the enhanced lateral growth is essential to grow thick GaN by the VPE with good crystalline quality free from the incorporation of the residual acceptors. |
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| Bibliography: | Schematic apparatus of a VPE system using GaCl 3 and NH 3 as precursors. Growth rates of GaN by the VPE using GaCl 3 plotted as a function of the growth temperatures. Surface morphologies of the VPE grown GaN on sapphire at (a) 925, (b) 975, and (c) 1000 °C. Surface morphologies of the VPE grown GaN on sapphire at 975 °C with the V/III ratios of (a) 50, (b) 300, (c) 500. XRD patterns of the the VPE-grown GaN film on sapphire. FWHM of X-ray rocking curve for the VPE grown GaN plotted as a function of the growth temperature. PL spectra of GaN grown at 800--1000 °C by VPE. Detailed PL spectra of GaN grown at 955--990 °C by VPE. |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.50.085501 |