Critical thickness for dislocation generation in epitaxial piezoelectric thin films

Abstract

Dislocations form in epitaxial thin films above a critical thickness, when the stress due to the film–substrate mismatch becomes excessive. This phenomenon has been extensively investigated in non-piezoelectric thin films. In piezoelectric films, the mismatch strain field and the electric field are coupled, and the critical thickness depends on an extra physical variable: the electric field. In this paper, the critical thickness for dislocation formation in a piezoelectric film is derived. The dependence of the critical thickness on the piezoelectric properties of the Al x Ga1− x N/GaN system is then discussed.