Theory of two boron neutral pair defects in silicon

Abstract

Using ob initio local densily calculalions, we consider lhe microscopic slruciures of two neutral pair deleas of B in Si. ?he s1111c1um are closely related IO propcued conligurations of the 'B-interstitial-related defect' in Si, with a B alom substituted for a Si atom. lhe B-split substitutional configuration has two empty, symmetrically equivalent, p orbitals, and may undergo (pseudo-) Jahn-Teller dirtorlions when negatively charged.supucell sire: the energy gained when relaxing the sccond-nearat-neighbour and funher away Si a t o m im Ihe larger 3Zalom cell is about 0.1 eV The band gap ermr due to the lml density appmimalion docs no1 mnlribule to the Lola1 energy, since, for lhe neutral defects a1 hand, all mcupied S t a h BR in the valence band. The p i l i o n s of the electmmie slates M accurate lo within about 05 cV, a s has been reported olher autho-, for a m p l e ,

First-Principles Modeling of Boron Clustering in Silicon

“…For one I, the structure does not depend on the number of electrons (which is identical for all B n I clusters), but strongly on the number of B atoms: for BI þ , we find a tetrahedral Si interstitial; for B 2 I 0 , we confirm the previously found h100i B dumbbell [10,11]; for B 3 I À , we find a bond-centered B interstitial between the two other B atoms; and for B 4 I ¼ , we calculate a 16 o tilted h100i dumbbell between the two other B atoms. For BICs involving two Is, the clusters contain triangular shapes; triangles form the surface of icosahedra, which form the structure of pure B.…”

“…In order to decrease the threat of finding a high-energy local instead of the global minimum, we started for each cluster from many different initial configurations that were structurally relaxed (including previously predicted ones from Refs. [10,11,16]. Further details will be published elsewhere [22].…”

“…However, fitting a large number of parameters in inverse modeling can be subject to ambiguities and furthermore does not help to identify the structure of the clusters. The second approach, atomistic calculations, especially within density-functional theory (DFT) [9][10][11][12][13][14][15], can in principle overcome these limitations; however, the problems to find global instead of local minima [16] and the possibly considerable error bars for miscoordinated defects [17] also require a cautious use of this approach. Until recently, only one set of BIC reaction barriers from first-principles [18] for B n I m (n 4) clusters had been available, where the influence of the different charge states had been neglected.…”

Theoretical Study of Boron Clustering in Silicon

“…We employed a harder variation of the B pseudopotential with a cut-off energy of 231.5 eV in GGA and 257.2 eV in LDA, respectively, and 64-atom supercells (216 atoms where described). For final cluster-energy calculations, 4 3 Monkhorst-Pack kpoint sampling was used (2 3 for 216-atom cells) and the atoms were fully relaxed such that the force on each atom was less than 0.03 eV/Å. For the exploration of the different charge states of the clusters in different configurations, 2 3 k-points were employed for Brillouin-zone sampling and a force-relaxation criterion of 0.05 eV/Å to enhance the computational efficiency [21].…”

“…First-principles pseudopotential calculations have been used to identify boron diffusion pathways and energetics [3][4][5][6]. A notable body of simulation work in order to model the boron clustering effect exists [7][8][9][10][11][12][13][14].…”