Mechanism of defect reactions in semiconductors

Abstract

We discuss mechanisms of defect reactions (defect creation, annihilation, multiplication, reconstruction, impurity diffusion, etc.) in semiconductors starting with the origin of the electron-lattice interactions. The key mechanism of extrinsic self-trapping is introduced to understand strong carrier localization and large accompanied lattice distortion. Symmetry-breaking structural instability is explained in connection with the Jahn-Teller effect. It is found that the tetrahedral coordination is not so rigid as it is considered, especially for hole localization. Next, we explain the true meaning of the configuration coordinate diagram (CCD), which is usually misused in literature. The multiphonon carrier capture and the following induced lattice relaxation processes are discussed using proper CCD for deep-level defects. Finally various mechanisms of defect reactions are discussed including instability mechanism and phonon-kick mechanism. Energy released by a carrier capture can enhance the next capture, and then for high carrier density, a positive feedback may occur to create a rapid increase of lattice vibrations, which then causes defect reactions.