Chapter 5 Intrinsic Point Defects in Silicon

Abstract

The chapter presents a discussion on the intrinsic point defects in silicon. The chapter discusses swirl defect manifestation of intrinsic point defects, thermal defects in silicon, point defects and self-diffusion, and several other related concepts. Evidence from a wide variety of experimental observations indicates that both the vacancy and the self-interstitial coexist in silicon in almost equal roles. They have comparable energies of formation and of migration. They all contribute to the self-diffusion and the diffusion of substitutional impurities in silicon; but their relative roles vary for different impurities. The silicon self-interstitial has a number of different configurations and moves through the lattice via different migration paths. First-principles total-energy calculations, using local-density approximation to achieve self-consistency in defect potential, have given some surprisingly good results that are compatible with experiments. But there are some limitations and the question of reliability of such calculations. Possible errors, some quite large, arise from two main causes: (1) the size of clusters or supercells, sufficiently large to avoid the convergence and dispersion problems, cannot be handled by modern computers; (2) the inherent problem of the inability of the local-density approximation to handle excited states.