Effect of Local Lattice Relaxation on the Electronic Structure of Substitutional Donors in Silicon

Abstract

The electronic structure of substitutional group V (P, As and Sb) and group VI (S, Se and Te, both neutral and singly ionized) impurities in silicon has been investigated using self-consistent Multiple Scattering Xa (MSXa) method within the framework of the standard muffin-tin potential approximation, incorporating the effect of lattice relaxation surrounding the impurity. A systematic study of the effect of local lattice relaxation on the electronic structure of group V (shallow) and group VI (deep) donors in Si is attempted. It is interesting to note that the size difference between the impurity atom and that of the host Si atom seems to be shared almost equally by the impurity atom (either expansion or squeezing) and the nearest neighbours (inward or outward movement). The effect of size difference on charge transfer and the bonding characteristics between the impurity atom and Si atoms are also analyzed.

Study of local lattice relaxation of substitutional impurities in silicon and germanium

“…The variation of binding energy with impurity radius is found to be nearly linear for all the impurities under study in both Si 9 and Ge 23. Similar trends have been reported by Li and Myles 7 in their study of S, Se, and Te deep levels in Si based on semiempirical nearest neighbor tight binding model.…”

“…As the impurities assume radii ( r ) different from that of host atom, the resulting displacements u , of the nearest neighbors are calculated as u = r − r host 9 and are given in Table III. Positive u implies that the nearest‐neighbor host atoms move outward, and vice‐versa.…”

“…Earlier 8, 9 the authors have investigated the effect of impurity introduced local lattice relaxation on group V and group VI substitutional donor states in Si, by two different methods, namely the first‐principle pseudo‐impurity theory proposed by Pantelides and Sah 10 and the multiple scattering Xα (MSXα) method by Johnson and Smith 11, 12.…”

“…The impurities chosen are group II (Be, Mg, and Zn) and group III (B, Al, Ga, and In) acceptors and group V (P, As, and Sb) and group VI (S 0 , Se 0 , Te 0 , S + , Se + , and Te + ) donors. To facilitate a comparative study, the results of substitutional donors in Si 9 are reproduced in the present work. The present study enables us to infer the chemical trends of some aspects of impurity states, such as local lattice relaxation and change transfer, of the impurities in two different elemental host systems, i.e., Si and Ge.…”

“…The present study enables us to infer the chemical trends of some aspects of impurity states, such as local lattice relaxation and change transfer, of the impurities in two different elemental host systems, i.e., Si and Ge. Since the details of the method (MSXα) 13 and the model used 9 in the present work were well documented earlier, no further descriptions are given here. The calculations are carried through to self consistency in potential to obtain an accuracy of 0.1 mRy in energy.…”