Initial Stage of Heteroepitaxial Growth of SiC on Si by Gas Source MBE Using Hydrocarbon Radicals
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TAKASHI FUYUKI, YOICHIRO TARUI, TOMOAKI HATAYAMA AND HIROYUKI MATSUNAMI Department of Electrical Engineering , Kyoto University, Yoshidahonmachi, Sakyo,Kyoto 606-01, Japan ABSTRACT Heteroepitaxial growth of 3C-SiC on Si in gas source molecular beam epitaxy GSMBE ) was carried out by a combination of carbonization of a Si surface and subsequent crystal growth on it using hydrocarbon radicals and Si2 H6 . The carbonization process and the initial stage of the subsequent growth during the intermittent supply of Si 2H 6 have been studied by a reflection high-energy electron diffraction (RHEED) observation. A Si surface was chemically converted to 3C-SiC at 750'C, and homoepitaxial growth on the carbonized layer could be obtained at 1000'C. Si atoms generated by thermal decomposition on a surface would react with hydrocarbon radicals, forming SiC through a layer by layer growth mode. INTRODUCTION Cubic silicon carbide (3C-SiC) is expected as a promising material for high temperature and power electronic devices. Crystal growth at low temperatures was investigated by GSMBE 15). Although high-quality 3C-SiC layers have been demanded in the 3C-SiC/Si heteroepitaxial system, the lattice mismatch ('-'20%) and the difference in thermal expansion coefficient (-8%) have deferred the growth of high-quality single-crystalline 3C-SiC. Carbonization of a Si surface developed by author's group may take an active part in reproducible growth of single-crystalline 3C-SiC 4,5). In the case of cracked propane (C 3H 8 ), a Si surface could be carbonized reproducibly at 750 0 C 5). The reason might be caused by chemically active hydrocarbon radicals generated by thermal cracking. A single-crystalline 3C-SiC layer could be obtained with disilaine (Si2 H6) and cracked C3 H8 as source gases in GSMBE at 1000°C 6). However, single-crystalline 3C-SiC with very smooth surfaces have not been obtained. Detail at analysis of a growing surface will be essential in order to understand a growth mechanism, leading single-crystalline 3C-SiC with a very smooth surface. In the present paper, the initial stage of carbonization of a Si(001) surface and layer by layer growth of 3C-SiC on it by intermittent supply of source gases were investigated using real time RHEED analysis. The growth mechanism and grown surface morphology are discussed.
201 Mat. Res. Soc. Symp. Proc. Vol. 318. 01994 Materials Research Society
EXPERIMENTAL The experimental apparatus was reported in detail elsewhere 1). A Si(001) wafer was used as a substrate. Prior to setting substrates in the loading-chamber, contamination and an oxidation layer on a substrate were removed by organic solvents and a HF solution. Si2 H6 and cracked C3 H8 were fed to a substrate surface through individual nozzles. C3 118 molecules were decomposed by a cracker cell whose temperature was measured by an optical pyrometer. The growth process was observed by a RHEED system. The intensity of diffraction spot was monitored by a video recorder. The thickness of grown layers was measured by ellipsometry, and surf
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