Charge transfer and charge conversion of K and N defect centers in Si3N4

Charge traps in silicon nitride and their interaction have been studied by first principle density functional theory (DFT) calculations. The K-0 (N-3=Si-.) and N-0 (Si-2=N-.) Si and N dangling bond centers, respectively, are electrically active paramagnetic point defects. They show an amphoteric behavior and convert into the more stable diamagnetic charged centers K- (N-3=Si-), K+ (N-3=Si+), N- (Si-2=N-), and N+ (Si-2=N+) The overcoordination of K+ and N+ and the electrostatic interaction with the K- or N- counterparts are important contributions to the negative-U character of the defects.