Electrical Studies of Neutron-Irradiated p-Type Silicon: Defect Structure and Annealing

Abstract

Defects produced in float-zone and crucible-grown p-type silicon by neutron irradiation at 76°K were investigated, using electrical conductivity and Hall-effect measurements. The behavior of the neutron-produced defects is independent of the crystal growth, and exhibits an illumination dependence similar to that previously observed in n-type silicon and attributed to the presence of defect clusters. The neutron-produced changes in the electrical properties of p-type silicon at 76°K are therefore ascribed to defect clusters. The annealing loss of the light-sensitive defects occurs in diffuse stages between 150° and 550°K. The largest stage is observed between 150° and 240°K. A major fraction of the hole-mobility annealing parallels the annealing for the light-sensitive defects, and suggests that the mobility change caused by defect clusters is significantly larger than that caused by isolated defects formed from cluster dissociation. The most apparent crystal-growth-dependent annealing is observed between 540° and 620°K, where a reverse annealing occurs in the hole-removal rate for crucible-grown, but not for float-zone, silicon. The fractions of the neutron-produced decreases in hole concentration and mobility which remain after 700°K annealing are, respectively, ∼0.1 and 0.01 for float-zone, and ∼0.25 and 0.1 for crucible-grown silicon.