Site distortion of the beryllium acceptor in germanium

Abstract

Beryllium in germanium is studied in high-resolution infrared transmission spectroscopy in the region of the $1s-2p$ transitions. The $1s-2p$ transitions are observed to be split in the absence of external perturbations. We interpret these data as demonstrating that the neutral substitutional beryllium impurity does not sit in the center of the germanium tetrahedron but is distorted, probably along a [111] direction.