Investigation of hydrogen effect on phosphorus-doped polysilicon thin films

Abstract

Polycrystalline silicon is widely used in microelectronic and photovoltaic applications. The main problem of this material is the recombination of charge carriers at the grain boundaries which affects the efficiency of the polycrystalline silicon solar cells. In order to improve the crystalline quality and the electrical properties of phosphorus-doped poly-silicon thin films, heat treatments under hydrogen were carried out. This allowed the occupation of the dangling bonds at the grain boundaries and made them inactive, which resulted in improved optoelectronic properties of the treated samples. It has been shown that the effect of hydrogen on the electrical characteristics is more pronounced for low doping concentrations where a 20% improvement of the free carrier concentration was obtained. In addition, the results have shown that the introduction of hydrogen in poly-silicon thin films reduces the density of trap states at the grain boundaries.

Annealing and Hydrogenation Effects on the Electrical Properties of Polysilicon Thin Films

“…The decrease in the resistivity with the increase in the annealing temperature is due to the decrease in the density of defects, which are capable of diffusing carriers at the grain boundaries, when the samples are annealed at high temperature. These results in the decreased resistivity and, therefore, the enhanced mobility of charge carriers as reported by Mekhalfa et al [13].…”