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To: unclewest who wrote (3104)	6/29/2000 5:55:00 PM
From: Robert C. Barry	Respond to of 10714

unclewest, I am not familiar with SiC crystals but have had in years past a lot of experience and knowledge of silicon crystals. Polycrystalline structures are the defect results of failed single crystalline processes. Basically, a crystal is pulled or zone refined from a seed with a particular millers index structure. The resultant ingot from that process must stay in the orientation of the seed. If that index is disturbed for some reason during the process (dirt, trauma etc.) a crystal will go "poly" or begin to grow in a direction other than the Millers index of the seed rendering the crystal essentially useless for most electronic uses. It can be ground for use on sandpaper or used as landfill. It seems that Cree is ahead of the pack in its ability to consistently make single crystal SiC in ever increasing diameters without having the pulled or refined crystal go polycrystalline on them. This is a huge competitive advantage for Cree and one that can be built upon. Pipes are defects in the single crystal structure caused usually by unwanted impurities. The resultant crystal can be used in a manufacturing process but generally produces a lower yielding poorer quality product. RCB

To: unclewest who wrote (3104)	6/29/2000 6:52:00 PM
From: sbaker23	Respond to of 10714

good explanation from the Yahoo board Datanite... by: AHZeeman 6/29/00 5:00 pm Msg: 28581 of 28593 From reading the patent, patent.womplex.ibm.com , Datanite is only suitable for low grade semiconductor applications as the fine surface detail is too poor for IC type epitaxy growth. This is why Sullivan is targeting the high current, low voltage market. The large area semiconductors used to support the high current flows are not as sensitive to the fine surface defects. I also assume that high voltage is out of the question as the surface defects will cause localised breakdowns at higher voltages. Nevertheless, there is a market for low voltage, high current and high efficiency semiconductors in applications such as electrolytic refining, electric arc furnaces and electric traction motors such as used in locomotives. Datanite is no threat to Cree in the area of LEDs, as the monocrystal structure of Cree's SiC is critical for proper LED epitaxy. messages.yahoo.com