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.

A fully self-consistent calculation using the multiple scattering X, method is used to study the electronic structure, the relation between charge transfer and electronegativity, the bonding characteristics, and the alloying of Mg with Al. The present investigation indicates that the charge transfer from the host A1 atoms to the central impurity atom increases with the increase of electronegativity of impurity atoms. It is found that the bonding is metallic for AlLMg and for the othcr impurities considered it gradually becomes ionic. The alloying of Mg with A1 is more favourable than with other impurities. The results are compared with the available experimental and theoretical data.

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rnWe report a fully self-consistent investigation of the electronic structure, relation between charge transfer and electronegativity, bonding characteristics, and alloying of Al, P, S, and C1 with silicon. The present study indicates that the charge transfer from the host Si atoms to the central impurity atom increases with electronegativity of the impurity element. The bonding between host Si atoms and the impurity atoms is ionic in nature. 0 1996 John Wiley & Sons, Inc. scattering x a (MSX a) method within the framework of the standard muffin tin potential approximation is used. This method, developed by Johnson and Smith E5, 61, has been successfully employed for defects in

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