First-principles study of migration, restructuring, and dissociation energies of oxygen complexes in silicon

Abstract

Migration, restructuring, and dissociation energies of oxygen complexes in silicon are studied theoretically through density-functional total-energy calculations. We find that the stablest oxygen complexes are straight chains that also have the lowest migration energies. The calculated migration energies decrease from 2.3 eV for an interstitial oxygen atom (O i ) to low values of 0.4 -1.6 eV for O 2 -O 9 chains and 1.9-2.2 eV for longer chains. The oxygen chains ͑which are thermal double donors͒ are expected to grow so that the migrating oxygen chains capture less-mobile but abundant O i 's: O n ϩO i →O nϩ1 . Restructuring energies of chains with a side O i into straight oxygen chains are 1.9-2.5 eV. Restructuring gives an essential contribution to the fast diffusion. We find that the shorter O 2 -O 9 chains dissociate primarily by ejecting one of the outermost oxygen atoms.

Comparison of oxygen-chain models for late thermal double donors in silicon

“…This model transcends those based on the di-Y-lid-type O chains because R-type O chains ͑i͒ have lower formation energies; ͑ii͒ have both increasingly delocalized spin densities of the double-donor states and increasing structural anisotropy, in agreement with experiments; and ͑iii͒ have much lower activation energies for migration which leads, when these energies are used in a kinetic model, to a close agreement with the experimentally found consecutive kinetics of TDDs. 14,18,20,21 Both the atomic structure and the spin density of the R-type O i -O nr -O i chains display alternating C 2v -C 1h symmetry, which is consistent with recent high-field EPR experiments. The spin densities of the double-donor states are located outside the region of the O atoms, consistent with the fact that the 17 O ENDOR lines show almost no hyperfine interaction.…”

Density-functional calculations of defect formation energies using supercell methods: Defects in diamond

“…[10][11][12][13] In addition, the kinetic properties of defects, such as diffusion mechanisms and migration energies, strongly depend on the charge state. [14][15][16] Moreover, chemical reactions involving bond formation and dissociation can also be explained in terms of the formation energy, provided it can be calculated with sufficient accuracy. 16,17 Systematic formation energy calculations have been performed for several semiconductors, including Si, [18][19][20] SiC, 21,38 GaN, 22 and diamond.…”

“…[14][15][16] Moreover, chemical reactions involving bond formation and dissociation can also be explained in terms of the formation energy, provided it can be calculated with sufficient accuracy. 16,17 Systematic formation energy calculations have been performed for several semiconductors, including Si, [18][19][20] SiC, 21,38 GaN, 22 and diamond. 14,[23][24][25] The formation energy E f of a defect with charge q is given by…”

Development of Radiation Hard Particle Detectors Made of Czochralski Grown Silicon

“…at temperatures that are frequently used in the detector processing. Studies based on computational methods suggest that the TD formation and thus shallow donor levels in silicon band gap are due to migration of oxygen complex chains [11,12].…”