Doping superlattices prepared by depositing successively 300Å thick layers of p-type, intrinsic, and n-type, intrinsic hydrogenated amorphous silicon respectively (pini structure), exhibit persistent photoconductivity (PPC) at room temperature.
The deposition of doping superlattices was carried out by changing the gas composition without extinguishing the plasma.
As the annealing temperature, which is higher than deposition temperature, is increased PPC decreases gradually. When annealing temperature, is 430℃, PPC disappears completely.
Therefore PPC does not appear to be caused by dangling bonds which is Su's argument and thus a new model is proposed.