The conversion of the carbon‐interstitial–phosphorous‐substitutional (Ci‐Ps) pairs from configuration M4 to M1 is shown to have a strong dependence on the method of sample fabrication. This conversion can be observed only in samples that have been contaminated by boron during sample fabrication. The temperature at which the conversion to M1 occurs is closely related to the level of boron contamination. In addition, it is shown that the M1 peak is not a single defect level. M1 consists of at least two overlapping levels that have similar properties but which are clearly related to different configurations. It is proposed that the conversion of M4 to M1 involves long‐range migration of boron interstitials and that the M1 configurations involve a boron interstitial trapped at an isolated Ci‐Pspair.