Study of Lithium Interaction with Lattice Defects in Silicon

A theoretical and experimental study is carried out on the behaviour of the Li donor impurity in the Si lattice with vacancy‐like (V) radiation‐induced defects. The electronic and geometrical structure of the cluster Si 4 H 12 + Li 4 simulating the V + Li 4 complex in Si is calculated by the discrete variational X α ‐method. It is found that the cubic tetrahedral configuration of the complex is geometrically stable where the 8t 2 state near the edge of the valence band is completely populated. The principal possibility of passivation of the V‐type defects by Li atoms is checked experimentally on n‐ and p‐Si samples with a Li concentration of ≈ 10 17 cm −3 irradiated by reactor neutrons at fluences of 1.6 × 10 15 , 4 × 10 15 , and 3.4 × 10 16 cm −3 . The temperature dependences of the conductivity, Hall constant, and mobility are measured. It is shown that at high Li atom concentrations considerably in excess of the concentration of the dopant and radiation‐induced defects the electrical characteristics of the irradiated Si restore to the original level which is in agreement with the calculations on the passivation of the Li atoms by the V‐states in Si.