Ain Grown by Metalorganic Molecular Beam Epitaxy

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J. D. MACKENZIE, C. R. ABERNATHY, S. J. PEARTON AND R. G. WILSON* Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 *Hughes Research Laboratory, Malibu, CA

ABSTRACT Thin film AIN has been grown on A120 3 and GaAs substrates by metalorganic molecular beam epitaxy (MOMBE) using amine bonded alane precursors, tertiarybutylamine, and nitrogen from a compact electron cyclotron resonance (ECR) plasma source operating at 2.45 GHz. Typical growth pressures were in the 0.5 - 1 x 10-4 Torr range. The growth rates, impurity backgrounds and surface morphologies were examined for both nitrogen sources and both the solid and liquid alanes. In general, growth efficiencies were good for both alane precursors, allowing for deposition of the low temperature, - 400'C, AIN buffers needed for subsequent growth of GaN and InGaAlN alloys. Low growth temperatures could not be obtained using tertiarybutylamine, presumably due to poor decomposition efficiency of the source at low temperatures. The structural quality of material grown at high temperatures from the ECR plasma was measured by atomic force microscopy (AFM) and high resolution x-ray diffraction (HRXRD), indicating a surface roughness of- 8 A and an x-ray full width half maximum (FWHM) of 430 arcsec.

INTRODUCTION Due to its high thermal conductivity and stability, chemical inertness, and ability to passivate Il1-V surfaces, there has been considerable interest in the growth of AIN films for microelectronics packaging, passivation and dielectric applications.' Recently, the development of blue-emitting optical devices 2 based on Group II-N materials as well as the potential for nitride-based high temperature electronic device applications have stimulated development of epitaxial growth techniques for AIN and Al-containing Group III-nitride ternaries of high electrical and optical quality. Several techniques have been investigated including metalorganic chemical vapor deposition (MOCVD),3 plasma-assisted molecular beam epitaxy (MBE),4 and metalorganic molecular beam epitaxy (MOMBE).5' 6 Problems inherent in methods based on metalorganic precursors include the incorporation of unwanted impurities including oxygen, hydrogen and carbon. Also, the use of plasma sources in UHV growth systems is a potential barrier to process scale-up and does not allow for selective growth based on catalytic Group V precursor decomposition. In this paper, the properties of films grown by MOMBE using different amine-bonded alane sources are compared. As well, the first attempt at UHV nitride growth with an amine precursor is reported.

EXPERIMENTAL AIN samples were grown on 2 inch diameter semi-insulating (100) GaAs substrates or (0001) sapphire substrates at 7000 - 725 'C in an Intevac Gas Source Gen II. Films grown with 213 Mat. Res. Soc. Symp. Proc. Vol. 363 ©1 995 Materials Research Society

the ECR nitrogen plasma were preceded by a low temperature AIN buffer grown with a substrate temperature of 425 TC. The aluminum sources, Trimethylamine alane (TMAA)