Grain boundaries play a major role in determining device performance, particularly of polysilicon-based photodetectors. Through the post-annealing of as-deposited polysilicon and then, the analysis of electric behavior for a metal-polysilicon-metal (MSM) photodetector, we were able to identify the influence of grain boundaries. A modified model of polysilicon grain boundaries in the MSM structure is presented, which uses a crystalline-interfacial layer-SiOx layer- interfacial layer-crystalline system that is similar to the Si-SiO2 system in MOS device. Hydrogen passivation was achieved through a hydrogen ion implantation process and was used to passivate the defects at both interfacial layers. The thin SiOx layer at the grain boundary can enhance the photosensitivity of an MSM photodetector by decreasing the dark current and increasing the light absorption.
