Vacuum Pressure MOVCD Growth and Characterization of AlN Films on MgO(100), Sapphire, and Si
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A. D. Serra , N. P. Magtoto , D. C. Ingram , H. H. Richardson Department of Chemistry, Ohio University, Athens, OH 45701, [email protected] Department of Physics, Ohio University, Athens, OH 45701, [email protected] ***Present Address: Department of Chemistry, University of Toronto, Toronto, Canada M5S I Al ABSTRACT Films of AIN were grown on MgO(100),
A12 0 3 ,
and Si under vacuum pressure
(10-3 to
10-4 Torr) at different substrate temperatures. They were examined ex situ with infrared
reflectance spectroscopy, scanning electron microscopy, x-ray diffraction and rutherford backscattering spectroscopy. Highly oriented smooth films were grown at film thicknesses below I ýtm. Thicker films showed significantly more roughness but remained oriented with respect to the substrate. AIN growth was faster on Si than MgO(100) or A120 3 and Si was the only substrate that growth was observed at 500 TC. INTRODUCTION The application of Group III-Nitride materials to microelectronic and optoelectric devices has gained a great deal of attention for several years now [1,2]. AIN and GaN are two semiconductors currently being studied as promising materials for blue/UV light emitting diodes because of their physical, chemical, and mechanical properties. Some of these properties include high heat conductivity, hardness, chemical stability, and high luminescence intensity [3,4]. Device applications using AIN and GaN semiconductors range from high density optical data storage and full color video-screens to simple traffic lights [5]. For example, using nitride based LED's compared to a typical 100 W incandescent light bulb would save up to 800 KW hours per year per traffic light [5]. With growing concerns for our energy resources, nitride based devices become a very attractive commodity. Considerable research has been directed at the growth and characterization of AIN and GaN epitaxial layers [6]. In spite of recent successes in GaN research, growing AIN films is far from being mastered because many challenging problems still remain [7]. One of the long standing problems in AIN growth arises from the thermal and lattice mismatch between AIN and the currently used substrates mainly sapphire. Our laboratory has explored growing AIN films on MgO(100) because the lattice parameters and thermal properties of MgO are comparable to those of AIN. Films on silicon and sapphire were also deposited for comparison. Growth conditions were varied (temperature and pressure) and films were grown simultaneously on silicon, sapphire and MgO(100). They were then characterized ex situ with respect to thickness, crystallinity, orientation, surface roughness and band-gap. EXPERIMENTAL Aluminum nitride films were grown in a stainless steel high vacuum reaction chamber by metal organic chemical vapor deposition (MOCVD). The system consists of a growth chamber, pumping station and gas delivery system. The growth chamber houses the substrate holder, heater assemble, thermocouple, pressure measuring device, optical windows, and
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