Method for improving electrical property of polysilicon film used to light absorption layer of photodetector

Abstract

In this study, various process methods were presented to improve the light response characteristics of polycrystalline silicon (polysilicon) for photodetector applications. The manufactured polysilicon is composed of grains and grain boundaries, and have a rectangular area for the light absorption. The dark current or photocurrent of a polysilicon-based photodetector is affected by the chemical state of the polysilicon grain and grain boundary where light absorption occurs. The electrical conductivity was investigated by varying the dimensions of the light absorption area to find the dependence of the number of grains in the absorption area. And then, we tried to find a way to control the conduction property of the polysilicon film through various subsequent processes. A good photodetector should show a large amount of photocurrent while keeping the dark current low. For this purpose, we found that an appropriate number of grains must be included in the area of the light absorption layer, and subsequent processes like thermal annealing or hydrogen ion implantation that can effectively passivate the dangling bonds of the grain boundary are required.