Substitutional doping of chemically vapor-deposited amorphous silicon

Dc conductivity, absorption coefficient, photoconductivity, and magnetoresistance of phosphorus-doped amorphous Si films prepared by chemical vapor deposition (CVD) have been measured as a function of doping ratio. These results indicate that phosphorus doping reduces localized states in the mobility gap, narrows the tailing width below the extended states, and that phosphorus donors form the impurity band at 0.15 eV below E_c at a doping ratio of about 1×10^-2. It is also found that electronic properties of CVD amorphous Si can be controlled in a wide range by substitutional doping of phosphorus atoms.