Deep Level Centers

Abstract

The deep level centers are determined by a short range potential in a tight binding approximation. Several models are discussed from a simple square well model with added Coulomb well (hydrogen model) for higher energy states. Typical donors and acceptors in different materials are depicted. Other theoretical models include perturbation methods, cluster calculation, super cell and Green’s function techniques. Semi-empirical tight binding approximations indicate supercomputer use. Jahn Teller effect. Crystal field theory, splitting of levels. Examples of deep centers in alkali halides, F-centers with typical energies listed, and others. Vacancies in covalent crystals. Self-interstitials. Anti site defects, hydrogen in Si. Substitutional defects replacing a vacancy. Symmetry aspects. Isoelectronic defects. Chalcogens in Si and tabulation of their energy. Oxygen in GaAs. EL2 and DX centers. Negative U-centers. Shallow/deep center instability. Metastable Lattice relaxation. Transition metal impurities, energy tabulation. Isoelectronic defects, charge character. Tabulation of deep center energies and effective crystal field splitting. Measured ionization energies in Ge, Si, GaAs, and CdS.