A study of poly-Si grain boundaries using Schottky barriers

Schottky barrier diodes using aluminum on p-type polycrystalline silicon have been fabricated. The contrast of the orientation of neighboring grains is observed after chemical etching of the surface. Comparing the surface etch-pits of the substrate with the electronic behaviors of the Schottky diode, we are able to identify the grain boundary effect. It is found that the low-angle boundary has little effect on the I-V characteristics since near ideal Schottky-I-V curves are obtained. The high-angle grain boundary, however, significantly alters both the I-V and low-frequency C-V plots. The experimental data indicate that recombination centers and traps are introduced resulting in an increase in recombination current and a reduction of the effective mobility. By incorporating charge trapping at the grain boundary and the formation of a potential spike, we obtain a self-consistent explanation to the experimental data.