Résumé
This chapter discusses the strain effects on nitride semiconductor compounds. The chapter describes some basic properties of strain and reviews some of the effects evidenced of intense investigations during the past decades of zinc-blende semiconductors. Residual strain-fields are always present in III-nitrides and in their related heterostructures. They can produce a reversal of the ordering of the valence band in bulk crystals under biaxial tension. The oscillator strengths of the optical transitions at zone center are extremely dependent on the biaxial strain. Growing a sample on a plane sapphire produces an anisotropic strain field and anisotropy of the in-plane optical response. The chapter discusses a state-of-the-art of the physics of strain effects for the III-nitrides and presents a correlation with similar phenomena in more classic zinc-blende semiconductors. The application of a homogeneous strain in a solid changes the equilibrium position of the atoms, the crystal symmetry, and the electronic band structure and the phonon spectrum.