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.