Structure, energetics, and extrinsic levels of small self-interstitial clusters in silicon

Abstract

Native defects in Si are of obvious importance in microelectronic device processing. Self-interstitials in particular are known to mediate, in many cases, anomalous impurity diffusion. Here we study the energetics and electronic structure of single, double, and triple self-interstitial clusters in crystalline Si in various charge states and geometries, providing extrinsic levels and binding-association-dissociation energies. We discuss the comparison of our results with some experimental data on self-implanted Si. We also reconsider the migration energetics of single interstitials in the light of recent experiments, and point out the possible role of cluster nucleation in the electrical activation of acceptor-implanted samples

Insights on the atomistic origin of X and W photoluminescence lines inc-Si fromab initiosimulations

“…We have used an energy cutoff of 550 eV and a 4 × 4 × 4 Monkhorst-Pack [28] Γ-centered k-point mesh for (i), (ii) and (iii) calculations. This simulation setup results in a denser k-point mesh [14] and larger energy cutoff [15,16] than previous studies. For (iv) calculations, we have used an energy cutoff of 150 eV and a 2x2x2 Monkhorst-Pack Γ-centered k-point mesh due to computational restrictions as we included 600 empty bands in the calculation.…”

“…They concluded that the W PL line was due to I 3 -I as I 3 -V did not introduce electronic states in the semiconductor gap. In contrast, Lopez et al did not find enough evidences to associate I 3 -I to the W line due to its high formation energy and the bad agreement of its donor level with the photon energy of the W line [15,16]. With respect to the X line, Carvalho et al suggested the tetra-interstitial Si cluster configuration proposed by Arai et al as X PL center, despite that its donor level did not agree with experimental values, and there were some discrepancies of the calculated LVMs with experiments [17].…”

“…We have evaluated (i) their donor level in the gap, which can be related with the PL photon energy; (ii) the defect induced modifications of the electronic band structure, which shows whether a defect might favor or not radiative recombinations; (iii) their LVMs at the Γ point from the matrix of the second derivatives of the energy with respect to the atomic positions, which can be directly compared to the peaks that appear in the phonon-side bands of zero-phonon lines in PL spectra; and (iv) the transition amplitudes at band edges for relevant k-points from the imaginary part of the frequency dependent dielectric function within the random phase approximation, which permits evaluating which defect candidate has a stronger transition amplitude. Band structure modifications and transition amplitudes have not been considered in previous studies on the identification of PL centers in c-Si [14,15,16].…”

“…Different studies using ab initio simulations tried to associate interstitial defect clusters with W and X PL lines of c-Si [14,15,16], but they showed contradictory results. Carvalho et al analyzed two tri-interstitial Si clusters as candidates for W PL center, the so called I 3 -I and I 3 -V [14].…”

Extraction of additional interfacial states of silicon nanowire field-effect transistors

“…Another possible reason might be the additional energy states due to the interstitial silicon atoms 27 in the channel, as interstitial silicon atoms can be injected from the oxidation front into silicon beam structure during the thermal oxidation process. 28 The model suggests that interstitial silicon atoms near the oxide/channel interface injected by sacrificial oxidation and following gate oxidation processes, which generated energy states near conduction band edge that evaluated in this letter.…”