Persistent photoconductivity in doping-modulated multilayers and compensated thin films of hydrogenated amorphous silicon

Abstract

Persistent photoconductivity (PPC) has been studied in doping-modulated (npnp. . .) hydrogenated amorphous silicon (a-Si:H) multilayers as well as compensated a-Si:H films. The builtin field in the multilayers is varied by changing the dopant concentrations. It is concluded that charge separation in this builtin field alone cannot explain PPC in these npnp. . . structures. Experimental evidence is presented to argue that PPC in layered as well as compensated films arises from special centers made of phosphorous-boron complexes, which are in poor communication with the rest of the material.