Piezospectroscopic analysis of mobile defects in semiconducting materials

The piezospectroscopic analysis of point defects allows to describe fixed defects embedded in a crystal environment of immobile atoms. This description works well when all atoms vibrate around fixed equilibrium positions and these vibrations are much faster than the time scale of the experiment while the equilibrium positions do not evolve within this time scale. For some defects this condition is not fulfilled at temperatures of the DLTS experiment, which somehow is reflected in a departure from what the theory predicts. On the other hand, systematic discrepancies between results of theoretical piezospectroscopic analysis and experiment can be a valuable source of information about a defect. We discuss how these re-orientation processes can be identified from the observed piezospectroscopic parameters for a number of defect complexes observed in silicon and germanium with the use of the high-resolution Laplace Deep Level Transient Spectroscopy.