NEUTRAL INTERSTITIAL IRON CENTER IN SILICON STUDIED BY ZEEMAN SPECTROSCOPY

The Zeeman effect of the interstitial iron defect in silicon has been investigated by high-resolution Fourier-transform spectroscopy. Two se ts of experimentally observed line spectra have previously been identi fied as optical excitations of neutral interstitial iron, Fe-i(0). The first set arises when an electron is excited to a shallow-donor-like state, Fe-i(0)+h nu-->Fe++e(-), where the electron is decoupled from t he Fe+ core whose ground state is a T-4(1) term. The second set arises when an excited electron of a, symmetry ii; coupled by exchange inter action to the Fe+ core, yielding a T-5(1) final stat. The Zeeman behav ior of these transitions is studied in order to verify the assignment of the states and the effective-mass-like character of the decoupled e lectron. Detailed information on the initial state and on the properti es of the iron core is gained. Experiments determine the multiplet spl itting of the T-4(1) and T-5(1) states due to spin-orbit interaction b ut large deviations from the Lande interval rule are observed, as well as a marked decrease in intensity for the high-energy components. Our analysis confirms that the T-4(1) and T-5(1) states are closely relat ed, and a dynamical Jahn-Teller distortion is suggested to be the domi nant mechanism responsible for the non-Lande behavior, [S0163-1829(98) 06036-6].