| This dissertation presents our study of the role of the Jahn-Teller effect for transition-metal defects in semiconductors. The significance of the static Jahn-Teller effect for these defects has already been well established. Therefore, we concentrate on the role of the dynamic Jahn-Teller effect.;The first problem we consider is the Jahn-Teller contribution to the zero-field splitting found in S-state ions. We describe in detail how the electronic spins are coupled to lattice vibrations, and show that this coupling gives rise to a zero-field splitting. We estimate that the Jahn-Teller contribution can reasonably account for 10%, and quite possibly more, of the zero-field splitting.;Next, we consider the role of the Jahn-Teller effect for interstitial transition-metal defects in silicon. We conclude that the almost total quenching of the orbital contribution to the g-value is a result of the delocalization of the electron wave function. However, we find that a Jahn-Teller reduction of the orbital contribution to the hyperfine constant is required to account for some of the observed hyperfine constants for Mn defects. So, we conclude that a proper description of these transition-metal defects in silicon must include the dynamic Jahn-Teller effect. Finally, we propose an experiment that would test this conclusion.;The final problem we consider is the transition of the dynamic Jahn-Teller effect to the static limit for the ('3)T(,2) (CRTIMES) (epsilon) problem. We show that the dynamic Jahn-Teller effect is characterized by a tunneling splitting that results from the spin-orbit interaction. We show how this tunneling splitting may be observed with various kinds of luminescence spectra. As an example, we analyze the V('3+) defect in GaAs, and demonstrate that there is a dynamic aspect to the Jahn-Teller coupling for this defect.;Based on the results of our work, we conclude that the dynamic Jahn-Teller effect plays a significant role for the transition-metal defects in semiconductors. |
