Isotope Effect in Electrical Characteristics of Polysilicon Based-Photodetector

Abstract

The electrical conduction of polysilicon can be improved through the passivation of defects located at grain boundaries. Most passivation proceeds by hydrogen bonding to dangling bonds of silicon. However, more research is needed on the reliability of the Si-H bond. A process using deuterium instead of hydrogen can be expected to improve the performance of silicon devices because Si-D bonds have much higher stability than Si-H bonds. In this study, we have investigated how the isotope effect appears in polysilicon applications. For this purpose, a photodetector composed of a polysilicon film incorporated with hydrogen or deuterium was prepared, and then, current–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{I}$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}\text{)}$</tex-math> </inline-formula> characteristics, photo response, and degradation thereof were investigated. Hydrogen and deuterium incorporation was performed by both furnace annealing and ion implantation methods. It was found that in order for the isotope effect to occur in polysilicon grain structure, the density of grain boundary must be maintained properly, and there must be no additional damage during the hydrogen or deuterium process. Through this study, it was confirmed that the electrical characteristics and the reliability of the polysilicon based-photodetector were improved by forming a Si-D bond inside the polysilicon with the furnace annealing.