| 摘要 |
A sapphire single crystal wafer 11 having a diameter not less than two inches and having an off-angled surface which is obtained by rotating an R (1-102) surface about an axis in a negative direction by a given off-angle not less than 2° is introduced in a CVD apparatus. While the sapphire substrate is kept at a temperature of about 950° C., a buffer layer made of gallium nitride or aluminum-gallium nitride is first deposited with an average thickness of 0.1-0.2 mum, and then an aluminum nitride single crystal layer is deposited with an average thickness not less than 2 mum. The thus obtained aluminum nitride single crystal layer does not have a significant amount of cracks, has an excellent piezoelectric property, and has a high propagating velocity.
|
