The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 29, 2002
Filed:
Nov. 01, 1999
Yukinori Nakamura, Nagoya, JP;
Tomohiko Shibata, Kasugai, JP;
NGK Insulators, Ltd., Nagoya, JP;
Abstract
A sapphire single crystal wafer having a diameter not less than two inches and having an off-angled surface which is obtained by rotating an R ( - ) 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 &mgr;m, and then an aluminum nitride single crystal layer is deposited with an average thickness not less than 2 &mgr;m. 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.