Effects of Susceptor Geometry on GaN Growth on Si(111) with a New MOCVD Reactor
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Cite this article as: MRS Internet J. Nitride Semicon. Res. 4S1, G3.53(1999) ABSTRACT: High quality GaN films on AIN buffer layers were grown on Si(l 11) with a new, commercial, two-injector vertical rotating disk MOCVD reactor (CVD, Inc.). It was found that the geometry of the susceptor greatly affected the structural quality of the epilayers on Si. For the original susceptor geometry, though single crystal GaN films could be obtained, the films were dark gray in appearance with a rough morphology, and the best x-ray rocking curve FWHM was 2.33 '. After modifying the susceptor geometry, transparent, mirror-like single crystal GaN films were obtained with the best x-ray rocking curve FWHM being 0.24'. Photoluminescence (PL) and infrared reflectance (IR) spectra of the grown films were compared. The film growth rate was found to increase with decrease of the growth pressure. A 2-D simulation of the flow, heat transfer, and chemical species transport in the reactor showed a more symmetric flow, larger velocity gradient, and lower upward velocity with the modified susceptor, which may be the main reason for the improvement of the structural quality of the films. I. INTRODUCTION GaN has attracted much research interest due to its potential application in optical, high temperature, and high power devices. Although high quality GaN films have been achieved by MOCVD growth, the mechanism is still not fully understood. Factors found to affect MOCVD growth of GaN include substrate properties,(I' any buffer layer and its growth conditions,1 21 epilayer growth temperature and pressure,'3 ' VIHI molar flow ratio,1 41 inlet flow rate and reactor configuration,'51 among others, but a careful control of these factors does not guarantee a high quality film. The growth of GaN on silicon is very difficult due to their large difference in lattice constant, crystal structure, and thermal expansion coefficient,161 yet silicon is a very attractive material since it offers the possibility of incorporating GaN devices in silicon devices. In this work, a new, commercial, two-injector, vertical rotating disk MOCVD reactor (CVD Equipment Corporation) was used to grow GaN on Si( 11). After experiencing difficulties with film growth using the standard geometry, we modified it and found that the susceptor geometry greatly affected the structural quality of the films. II. EXPERIMENT A new, commercial MOCVD system (CVD, Inc.) was used for GaN growth. It consists of a gas delivery system, pumping system, and reaction chamber. The reaction chamber is G 3.53 Mat. Res. Soc. Symp. Proc. Vol. 537 © 1999 Materials Research Society
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