A transmission electron microscopy investigation of SiC films grown on SiC substrates by solid-source molecular beam epi
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A transmission electron microscopy investigation of SiC films grown on SiC substrates by solid-source molecular beam epitaxy U. Kaiser Institut fu¨r Festkdo¨rperphysik, Friedrich-Schiller-Universita¨t Jena, Max-Wien-Platz 1, D-07743 Jena, Germany
I. Khodos Institute of Microelectronics Technology and High Purity Materials RAS, 142432 Chernogolovka, Russia
P.D. Brown Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
A. Chuvilin Institute of Catalysis, Novosibirsk 90, 630090 Russia
M. Albrecht Institut fu¨r Werkstoffwissenschaften, Universita¨t Erlangen, Cauerstrasse 6, D-91058 Erlangen, Germany
C.J. Humphreys Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
A. Fissel and W. Richter Institut fu¨r Festko¨rperphysik, Friedrich-Schiller-Universita¨t Jena, Max-Wien-Platz 1, D-07743 Jena, Germany (Received 17 August 1998; accepted 14 April 1999)
The relationship between the defect microstructure of SiC films grown by solid-source molecular-beam epitaxy on 4H and 6H–SiC substrates and their growth conditions, for substrate temperatures ranging between 950 and 1300 °C, has been investigated by a combination of transmission electron microscopy and atomic force microscopy. The results demonstrate that the formation of defective cubic films is generally found to occur at temperatures below 1000 °C. At temperatures above 1000 °C our investigations prove that simultaneous supply of C and Si in the step-flow growth mode on vicinal 4H and 6H substrate surfaces results in defect-free hexagonal SiC layers, and defect-free cubic SiC can be grown by the alternating deposition technique. The controlled overgrowth of hexagonal on top of cubic layers is demonstrated for thin layer thicknesses.
I. INTRODUCTION
In view of the operation limits of silicon based devices, there is increasing interest in silicon carbide as a promising wide band-gap semiconducting material operating at high power, temperature, and frequency.1 There is also the intriguing possibility of forming novel heterostructure devices because SiC is a well-known polytypic material.2,3 The polytypes of SiC have been intensively studied and their defect microstructures have been wellcharacterized by means of transmission electron microscopy (TEM).4–10 At temperatures higher than 1300 °C the growth of defect-free cubic or hexagonal polytypes has been reported by a number of authors11–15 using chemical vapor deposition (CVD) or the sublimation 3226
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J. Mater. Res., Vol. 14, No. 8, Aug 1999 Downloaded: 31 Mar 2015
technique. However, use of the large 0.9-eV band-gap difference between the cubic (3C) and hexagonal (4H) SiC polytypes can be fully realized only if layers are grown defect-free in a controlled fashion at lower temperatures because such a regime would be required for modulation doping of future device structures. Perfect SiC is general
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