Symmetry and structure of N–O shallow donor complexes in silicon

Abstract

Shallow donors in silicon related to nitrogen–oxygen complexes have been investigated by piezospectroscopy of their hydrogenic transitions in the far infrared. Complete stress dependences up to 0.25GPa were obtained for the 1s→2p0 and 1s→2p± transitions of the most prominent members of the (N, O)-family, N–O-3 and N–O-5. Very unusual for shallow donors in silicon, the symmetry of the ground state wave function is T2-like. The lifting of orientational degeneracy for stress in the 〈100〉, 〈111〉, and 〈110〉 directions is compatible with a C2v defect symmetry. Data from the other species of the (N, O)-family are indicative for the same symmetry. The microscopic structure of these centers, in part contradictory to present theoretical models, is discussed.