ROLE OF FREE-CARRIERS IN THE APPLICATION OF OPTICALLY DETECTED MAGNETIC-RESONANCE FOR STUDIES OF DEFECTS IN SILICON

The influence of free carriers on optically detected magnetic resonance (ODMR) signals for defects in silicon is discussed. The presence of free carriers induces a strong background signal in the ODMR spectrum due to carrier heating effects in a microwave field. This background signal often obscures a possible detection of a defect-related magnetic resonance signal and is therefore highly undesirable. To avoid this problem, a delayed ODMR (D-ODMR) technique is employed. On the other hand, the presence of free carriers provides a medium for a possible ODMR detection of nonradiative defects. This is realized by a shunt pass of carrier recombination at such defects, which competes with the radiative carrier recombinations detected optically, and gives rise to negative ODMR signals for the defects responsible for the nonradiative recombination. Typical examples from recent studies of these different cases of defects in silicon are demonstrated.