The Growth and Characterization of Large Diameter Silicon Carbide Substrates
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The Growth and Characterization of Large Diameter Silicon Carbide Substrates A. Gupta, M. Yoganathan, J. Burton, N. Byrd, A. Dimondi, S. Edwards, A. Giordana, J. Glesener, J. Harding, F. Long, 1W. Mitchel, 1A. Saxler, R. Sostak, J. Whitlock, R. N. Thomas, T. Anderson Electronic Materials Group Litton Airtron 200 E. Hanover Avenue Morris Plains, NJ 07950 1 Air Force Research Laboratory Wright-Patterson AFB, OH 45433
ABSTRACT Affordable, high quality SiC wafers are very desirable for a variety of new technologies including GaN based lighting, RF, and high-power electronics based on wide band gap materials. At Litton Airtron we have a major effort in the growth and characterization of SiC. We will present data on 35, 50 and 75-mm diameter crystals. We are growing both n-type, semiinsulating 4H, 6H, and 15R material. A variety of characterization techniques are being used at Litton Airtron to determine wafer quality. These include Raman microscopy, digital wafer photography, and crossed polarizer images. Raman spectroscopy is an excellent probe of polytype and carrier concentration for n-type materials; in addition it can be done at room temperature and is sufficiently fast that it can be used in an industrial environment. The use of digital photography allows for the collection of images that can be quantitatively analyzed and archived. INTRODUCTION Wide band gap semiconductors are an attractive materials technology for the next generation of solid-state radar and power switching devices. Wide band gap semiconductor technology would reduce the size, weight, and cost from those of existing systems and offer orders of magnitude improvement in performance and operational simplicity. There are also significant potential commercial markets for SiC electronics. Ten percent of the electricity used in the US is for computers and telecommunications equipment, which require conditioned electrical power. Further development of these electronic devices requires improved SiC (silicon carbide) substrates. Alternatives such as sapphire are not really suitable due to substrate bowing problems on wafers larger than two inches in diameter. Furthermore sapphire is also problematic because of a large lattice mismatch with GaN (gallium nitride) and AlGaN (aluminum gallium nitride). The problem of lattice mismatch is significantly diminished with SiC substrates. Of course bulk GaN would be the ideal substrate for GaN epilayers; however, high quality, large diameter, single crystal GaN or AlN substrates have not yet been demonstrated. In this paper we discuss the growth and characterization of two-inch diameter 4H n-type SiC, 6H semi-insulating wafers, and 50-mm diameter wafers of 15R SiC. To the best of our knowledge, high quality 50-mm diameter 15R SiC wafers have not been previously produced. H5.2.1
EXPERIMENTAL DETAILS
The SiC was grown by physical vapor transport[1]. Typical growth temperatures were above 2000° C. These temperatures were obtained by heating a graphite cylinder with RF coils. For the growth of semi-insulating SiC, va
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