Dopant compensation effects on impurity trapping and electrical resistivity of ion implanted amorphous silicon

The implantation of B and P in ion‐implanted amorphous Si has been investigated by measurements of spreading resistance and depth distribution of Pd trapped at defects. For concentrations of B or P in the range 0.2–1 at. %, the resistivity is reduced by an order of magnitude and the Pd trapping is retarded by the presence of B and enhanced by P. When B and P are present together at comparable concentrations the resistivity and the trapping efficiency of amorphous Si return to the undoped value. These compensation effects are explained in terms of the dopants changing the Fermi level position and hence the charge state and trapping efficiency of the defects. It is argued that most of the defects (∼1 at. %) are chargeable. These results provide a clue for understanding the dopant compensation phenomena observed in the rate of epitaxial crystallization of amorphous Si.