Direct Evidence of Phosphorus-Defect Complexes in n -Type Amorphous Silicon and Hydrogenated Amorphous Silicon

We use positron annihilation spectroscopy (PAS) to identify the phosphorus-defect complex (*D^-) in n-type hydrogenated amorphous Si ( a-Si:H). The positrons are attracted and localized at the small open volume associated with the dangling bond defects. The radiation detected after annihilation gives a characteristic P signature, regarded as a *D^- ``fingerprint.'' Additional evidence is obtained from a comparison to P-implanted amorphized Si, as well as from theoretical calculations. This work lays the foundation for PAS studies of impurity-defect related processes in a-Si:H.