Depletion of charge carriers in electronic polycrystalline silicon

Abstract

Silicon Si is the material of choice for reliable and low-cost different applications in nano- and optoelectronics, from integrated circuits (IC) to TFTs and flat-panel displays. Some processes taking place in polycrystalline Si samples of finite length; for example, carrier depletion, is of particular interest. Until now processes of carrier depletion were studied only for monocrystalline Si and Ge. Here, we report for the first time the results of the studies carried out in polycrystalline Si specimens of n-type conductivity at room temperature in order to clarify the effect of crystal structure on electric field-induced properties. Samples with columnar and grain type of crystal structure were chosen for simplest non-destructive electric investigations. It was shown that depletion of carriers was observed in samples of columnar crystal structure; at the same time, specimens of grain type structure showed a synthetic mechanism: exclusion+tunneling of carriers through intergranular boundaries. The effect of heat treatment of the samples under 900 and 1100 °C on the described properties was also studied. The experimental results are numerically modeled, and a summary of investigations seems to be useful for future applications of polycrystalline Si.