Structure, thermal expansion and optical property of alumina-rich spinel substrate

Alumina-rich spinel is a new substrate for fabricating high-quality GaN-based light-emitting diodes. 1:3 spinel crystals (1 MgO for 3Al2O3) with dimension of diameter 36 mm × 55 mm have been grown by the Czochralski method. The crystal structure and lattice parameters were evaluated by single-crystal X-ray diffraction. The thermal expansion coefficient is 8.1508 × 10−6 K−1 in the temperature range from 30 °C to 1000 °C. The optical transmission studies show the grown crystal possesses good optical transparency with no magnesium deficiency absorption peaks.