First-Principles Study of Defect Levels Caused by Transition Metal Atoms in Silicon Nitride for Non-Volatile Memory Applications

Abstract

We have analyzed the nature of the transition metal (Ti, V, or Mn) defects in β-silicon nitride using first-principles calculations. Three supercells consisting of 168 atoms, termed as Si71N96Ti, Si71N96V, and Si71N96Mn, were derived from the supercell Si72N96 by substituting a Si atom with a transition metal atom. The density of states (DOS) were calculated for all the supercells. In Si71N96Mn, several defect levels appeared in bandgap. Some of the defect levels are energetically deep. Atomic Layer DOS (ALDOS) calculations have confirmed the localization of the defect levels around the Mn atom. Some of the defect levels would be able to behave as deep electron trap sites. Several defect levels also appeared in the supercell Si71N96V. On the other hand, in Si71N96Ti, no deep defect levels appeared in the bandgap.