Arsenic-doped Films Research Articles

Dopant Segregation and Heat Treatment Effects on the Electrical Properties of Polycrystalline Silicon thin Films

This paper reports the effect of heat treatment on the electronic activity of grain boundaries of polycrystalline silicon. The results obtained show that for the same concentration of doping, the arsenic doped films are more resistive and have less free carriers than boron doped films. The arsenic atoms have a greater tendency to segregate at the grain boundaries than boron atoms. We also noticed that the heat treatment before implantation reduces the number of trap carriers and the quantity of doping atoms at the grain boundaries. For low doping, the concentration of the free charge carriers improves after the heat treatment by 100 % and 23 % for arsenic and boron doping respectively.

Hydrogenation Effect on Electrical Behavior of Polysilicon Thin Films

Despite their wide availability and relatively low prices, the conventional energy sources have harmful consequences on the environment and are exhaustible. In order to circumvent these negative effects, the renewable energies in general and the photovoltaic energy in particular are becoming more and more attractive. In this type of conversion, the low cost polycrystalline silicon solar cells are promising. However, the photovoltaic parameters of these cells are affected by the existence of the grain boundaries (GBs) and the segregation of impurities at these GBs. In this work, we are interested in studying the effect of hydrogenation on the electrical behavior in polysilicon thin films. The results have shown that the introduction of hydrogen in a polysilicon films reduces the density of trap states at the GBs, and hence their electronic activity. This is translated in the reduction of the resistivity, the improvement the mobility of carriers and an increase in the concentration of free carriers. In addition, it has been shown that the effect of hydrogen on the electrical characteristics is more pronounced, on the one hand, for low doping concentrations, and on the other hands, in boron doped films than in arsenic doped films. This is mainly due to the strong segregation of arsenic atoms at the GBs, which reduces the effect of hydrogen on the density of trap states by reducing its penetration in the GBs.

Grain Growth in Polycrystalline Silicon Films

ABSTRACTExperimental observations of recrystallization, normal grain growth and secondary grain growth in silicon films are reviewed. Normal grain growth leads to grain sizes which are approximately equal to the film thickness. Secondary grain growth can lead to larger grains with restricted crystallographic textures. These procesess are affected by the as-deposited or as-crystallized grain structures and orientations. The rate of grain growth has been shown to be higher in phosphorous or arsenic doped films. Ion bombardment, oxidation, and interactions with silicides also lead to increased grain growth rates. Grain growth enhancement has been related to increased point defect concentrations or dopant redistribution.