Site symmetry and deformation-potential constants of Al-Xacceptors in silicon

Abstract

A quantitative piezospectroscopic study of the acceptor spectrum of X centers of aluminum in silicon shows that, in contrast to the group-III acceptors in silicon, they have a trigonal rather than the tetrahedral symmetry with preferred axes along the 〈111〉 direction. Uniaxial stress along the 〈111〉 and 〈110〉 directions separates these centers into two inequivalent sets with 1:3 and 1:1 ratios, respectively. However, the 〈100〉 stress leaves them unaffected. Deformation-potential constants associated with the lifting of orientational degeneracy and those corresponding to the excited states of the impurity are determined.