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Large sapphire crystals for 200-mm LED wafers were successfully grown by the top seeded melt growth (TSMG) method. The sapphire had excellent crystallinity as LED substrates. However, in the as-grown crystal, there was remarkable absorption in UV region caused by the F-center (V Â O ). To reduce the absorption, we studied several heat treatment methods using oxidized atmospheres. In air or O 2 atmospheres, the absorption was difficult to reduce because oxygen diffusion was slow and new absorption occurred. We found that heat treatment in an H 2 O 2 combustion flame was highly effective in reducing the absorption in the UV region. After the combustion flame heat treatment, the sample had an absorption coefficient less than 0.5 cm 1 at 200 nm, and no photoluminescent emissions were caused by color centers. Consequently, sapphire crystals grown by the TSMG method had good crystallinity and low absorption in the UV region.

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