Charge traps, and their interaction, were studied by using first-principles density functional theory calculations. The K0 (N3=Si▪) and N0 (Si2=N▪) Si and N dangling-bond centres, respectively, were electrically active paramagnetic point defects. They exhibited an amphoteric behavior, and changed into the more stable diamagnetic charged centres, K- (N3=Si-), K+ (N3=Si+), N- (Si2=N-) and N+ (Si2=N+). The over-coordination of K+ and N+, and the electrostatic interactions with the K- or N- counterparts, made important contributions to the negative-U nature of the defects.

Charge Transfer and Charge Conversion of K and N Defect Centres in Si3N4. G.Pacchioni, D.Erbetta: Physical Review B, 2000, 61[22], 15005-10