Aluminum nitride-silicon carbide solid solutions grown by plasma-assisted, gas-source molecular beam epitaxy
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Aluminum nitride-silicon carbide solid solutions grown by plasma-assisted, gas-source molecular beam epitaxy R. S. Kern,a) L. B. Rowland,b) S. Tanaka,c) and R. F. Davis Department of Materials Science and Engineering, North Carolina State University, Box 7907, Raleigh, North Carolina 27695-7907 (Received 21 March 1997; accepted 14 August 1997)
Solid solutions of aluminum nitride (AlN) and silicon carbide (SiC) have been grown at 900–1300 ±C on vicinal a(6H)-SiC(0001) substrates by plasma-assisted, gas-source molecular beam epitaxy. Under specific processing conditions, films of (AlN)x (SiC)12x with 0.2 < x < 0.8, as determined by Auger electron spectrometry (AES), were deposited. Reflection high-energy electron diffraction (RHEED) was used to determine the crystalline quality, surface character, and epilayer polytype. Analysis of the resulting surfaces was also performed by scanning electron microscopy (SEM). High-resolution transmission electron microscopy (HRTEM) revealed that monocrystalline films with x > 0.25 had the wurtzite (2H) crystal structure; however, films with x , 0.25 had the zincblende (3C) crystal structure.
I. INTRODUCTION
A marked increase in the interest in wide band gap semiconductor materials for use in high-temperature, high-power, high-frequency, and high-speed microelectronic devices resistant to radiation and for shortwavelength optoelectronic devices has recently been demonstrated on a global scale. Of these materials, SiC and AlN are two of the most studied. One method of exploiting the favorable characteristics of both of these materials is the deposition of thin film alloys. Silicon carbide is the only binary compound of Si and C that is stable at atmospheric pressure. Approximately 250 SiC polytypes having different stacking arrangements along the closest packed direction and cubic, hexagonal, or rhombohedral unit cells have been reported.1 The hexagonal and rhombohedral polytypes are collectively referred to as a –SiC, while the only cubic (zincblende) structure is referred to as b –SiC. The most common of the former is 6H-SiC with a room temperature band gap of ø3.0 eV. The cubic polytype has a room temperature bandgap of 2.3 eV, and is commonly referred to as 3C-SiC. The numerals refer to the number of closest packed SiyC bilayers necessary to make a unit cell; the letters refer to the unit cell
a)
Present address: Hewlett-Packard Optoelectronics Division, San Jose, California 95131. b) Present address: Northrop Grumman Corporation, Electronic Sensors and Systems Division, Pittsburgh, Pennsylvania 15235. c) Present address: The Institute of Physical and Chemical Research (RIKEN), Saitama 351-01, Japan. 1816
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 7, Jul 1998
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crystallography. All polytypes studied to date indicate an indirect band gap. Aluminum nitride normally forms in the wurtzite (2H) structure where it possesses a direct band gap2 of 6.2 eV at room temperature, a dielectric constant3
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