First principles calculations of solution energies of dopants around stacking faults in Si crystal

Abstract

First principles calculations were performed to investigate the recent transmission electron microscopic observations of the dislocation cores of heavily doped n- and p-type Si crystals. Segregations around the stacking fault region of p-type (Ga, Al, In) and n-type (P, As, Sb) dopants were confirmed by the solution energy differences of the location sites between the perfect lattice and stacking fault. These solution energy changes are caused not by the interlayer relaxations around the dopants but by the electronic structure changes near the band gaps.

Segregation mechanism of arsenic dopants at grain boundaries in silicon

“…The energy lowering of 0.15 eV is identical to the segregation energy at the site. This is consistent with segregation models that the binding energy of As atoms at Σ5{310} [58] and Σ3{111} [59] GBs is increased via the interaction with local energy levels generated at the GBs. Meanwhile, the donor level at the site 8 would be raised by about 0.2 eV, and the partial density of state (PDOS) at E F is significantly lowered in comparison with at the bulk region.…”

“…We hypothesize that As atoms would prefer to segregate at 5-membered rings via anisotropic bond distortions spontaneously introduced so as to lower the donor level, as Jahn-Teller distortions, even when the sites are unfavourable to segregate from an elastic point of view. Similar segregation characteristics can be observed for other donors such as phosphorus [15,59,62], antimony [45] and sodium [63].…”

“…It is reported that As atoms can segregate at stacking faults (SFs) bound by dislocations [74], including an atomistic structure similar to Σ3{111} GBs [75]. The As segregation is attributed to the electronic structure changes near the band gaps rather than to the elastic interactions [59], similar to the segregation mechanism discussed in Sec. 3.2, and the segregation energy due to the electronic interaction is estimated to be 0.07 eV [59,76].…”

Nanoscopic analysis of oxygen segregation at tilt boundaries in silicon ingots using atom probe tomography combined with TEM and ab initio calculations

“…Since oxygen atoms in the isolated form are not a dopant, i.e. they act as neutral impurities when they locate at the bond‐centred interstitial sites, they would not induce complicated electronic effects (extended carrier behaviours around impurity ions or drastic configurational changes of impurity atoms to localize such carriers) (Arias & Joannopoulos, ; Kohyama, ; Yamamoto et al ., ). Therefore, they would adopt atomic sites that reduce the overall lattice distortions.…”

“…Oxygen atoms did not agglomerate at pure Σ3{111} GBs (Stoffers et al ., ; Ohno et al ., , ). This indicates that the intrinsic segregation levels of the GBs is rather small, as theoretically expected (Yamamoto et al ., ), because of no dangling bond and little bond distortion at the GBs (Kohyama, ).…”