MOVPE growth optimization of high quality InGaN films.
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Internet Journal o f
Nitride S emiconductor Research
Volume 2, Article 16
MOVPE growth optimization of high quality InGaN films. W. Van der Stricht, I. Moerman, P. Demeester University of Ghent-IMEC, Department of Information Technology L. Considine, E. J. Thrush, J. A. Crawley Thomas Swan & Co., Ltd. This article was received on June 5, 1997 and accepted on August 6, 1997.
Abstract In this paper growth of high quality InGaN films on (0001) sapphire substrates by atmospheric pressure organometallic vapour phase epitaxy in a vertical rotating disk reactor is investigated. The InGaN layers grown above 800 °C are transparent and show no In-droplets on the surface. The In-content varies between 56 and 9 % for growth temperatures between 700 and 850 °C. The DC X-ray rocking curve of InGaN typically shows a FWHM between 8 and 15 arcmin. Room temperature PL shows an intense band edge emission with a FWHM between 100 and 200 meV for an In-content of 9 and 56 %. The initial efforts on QW growth are discussed.
1. Introduction Recently the group III-nitrides (In, Ga)N have attracted much attention because of the high potential for the fabrication of light emitting devices operating in the red to ultraviolet wavelength range. Despite the recent success in realizing devices, only few reports have been made on growth of InGaN. In this paper growth of high quality InGaN films on (0001) sapphire substrates by atmospheric pressure organometallic vapor phase epitaxy in a close spaced vertical rotating disk reactor is investigated. The effect of several growth parameters on the indium incorporation and the optical quality of InGaN films and InGaN/GaN quantum wells is investigated. The layers are characterized by optical microscopy, DC X-ray and 300 K photoluminescence measurements.
2. Experiment InGaN films and quantum wells were grown by metalorganic chemical vapour deposition on two inch sapphire (0001) substrates with nitrogen carrier gas. Ammonia (NH3), trimethyl-gallium (TMG) and trimethyl-indium (TMI) were used as source materials. The growth was conducted in a close spaced vertical rotating disk reactor, manufactured by Thomas Swan & Co [1] [2]. Deposition was performed under atmospheric pressure. The InGaN films were deposited on 2 micron thick GaN layers, because the lattice constant of InGaN is closer to GaN then sapphire. The growth was performed with a high indium source flow rate and nitrogen carrier. This is necessary because the indium incorporation is very low at growth temperatures in the range of 700 to 850 °C [3]. Typical flow rates for carrier, NH3, TMG and TMI are 4 l/min, 2.5 l/min, 5.6 µmol/min and 22.7 µmol/min. The V/III ratio was varied between 5200 and 5900. The thickness of the InGaN bulk layers varied between 0.4 and 0.2 micron. The InGaN quantum wells were imbedded in GaN layers grown at low temperatures, where the top layer has to prevent the decomposition of the quantum well while ramping up to 1050 °C (GaN growth temperature). The InGaN films were characterised by X-ray measurements to examine t
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