Ab Initio Study of MgSe Self-Interstitial (Mgi and Sei)

We present detailed calculations of formation and thermodynamics transition state energies of Mgi and Sei interstitial defects in MgSe using generalized gradient approximation (GGA) and local density approximation (LDA) functional in the frame work of density functional theory (DFT). For both LDA and GGA the formation energies of Mgi and Sei are relatively low in all the configurations. The most stable Se interstitial was the tetrahedral (T) configuration having lower formation energy than the decagonal (D) configuration. The Mgi and Sei defect introduced transition state levels that had either donor or acceptor levels within the band gap. Sei acts as a donor or an acceptor and creates levels that were either deep or shallow depending on the configuration. Sei exhibit negative-U properties and show charge states metastability in the D configuration. Mgi acts as only shallow donor (+2/ + 1) in both T and D configurations, in addition we pointed out the role of Mgias electrically activating donor.