INFRARED STUDY OF (H,BE)-ACCEPTOR, (D,BE)-ACCEPTOR, AND (LI,BE)-ACCEPTOR COMPLEXES IN SILICON

The temperature and stress dependences of the p1/2-series 2p line for the acceptors (Li,Be), (D,Be), and (H,Be) in silicon have been measured. The results demonstrate that (Li,Be) is a fixed 111-oriented defect with a ground state split by local distortion and that (D,Be) and (H,Be) undergo either tunneling or hindered rotor motion. A far-infrared study of the ground-state splitting of (Li,Be) also reveals an unexpected 4-cm-1 line that, based on temperature-dependent infrared spectra, we have attributed to the neutral double-acceptor Be. Our results for (Li,Be) provide a standard to which the unusual features in the temperature and stress dependences of (D,Be) and (H,Be) can be compared. For both (D,Be) and (H,Be) we find a blue-shifted replica of the 2p line and a ground-state manifold consisting of at least three well-resolved energy levels. This multiplet is explained by a tunneling model which we extend to give quantitative formulas for the stress dependence. Comparison of the model with our stress data provides additional evidence that (D,Be) and (H,Be) either tunnel or rotate between equivalent equilibrium orientations and that these orientations are along 111 directions, contrary to the results of recent numerical simulations. © 1990 The American Physical Society.