The nature of the dominant deep trap in amorphous silicon nitride films: Evidence for a negative correlation energy

A recent study by Krick and coworkers provided the first direct evidence associating a specific point-defect with trapping phenomena in silicon nitride films. Krick and coworkers demonstrated that silicon "dangling bond" centers in silicon nitride films are electrically neutral when paramagnetic and are rendered diamagnetic when they trap an electron or a hole. We show that these centers exhibit behavior consistent with a negative electron-electron correlation energy, a so-called negative U. With a negative U there is a strong attractive interaction between spin-up and spin-down electrons on the same dangling bond site. This attractive interaction implies that, in thermodynamic equilibrium, nearly all of the defect sites will be diamagnetic - either positively or negatively charged.