Origin of Persistent Photoconductivity in Modulation Doped Amorphous Silicon Multilayers

ABSTRACTWe show that persistent photoconductivity (PPC) observed in npn … multilayers of hydrogenated amorphous silicon (a-Si:H) and compensated thin a-Si:H films have a common origin. It is caused by special centers lying in the upper half of the mobility gap. The centers are not related to the presence of argon during deposition. Similarities of PPC between the layered and compensated films are shown. We also find that PPC in compensated samples, is not entirely a surface effect. Experiments are suggested to decide whether these centers are P-B complexes or can arise from the presence of boron alone.