Structure and optoelectronic properties as a function of hydrogen dilution of microcrystalline silicon films prepared by hot wire chemical vapor deposition

摘要

Films prepared by hot wire CVD using H dilution ratio, R=H_2/SiH_4, from 1 to 20 were studied by X-ray, Raman, PL, and conductivity measurements. We found that (a) when the dilution ratio reached R=3, the structure transition from amorphous to microcrystalline growth occured; meanwhile, PL spectrum showed a dual-peak at 1.3 and 1.0 eV; (b) the total intensity, band width, and peak position of the low energy PL band decreased with increasing H dilution; (c) both the Raman and PL measured from the transparent substrate side showed that initial growth tends to be amorphous and a portion of mu c-Si was formed when R>=5; and (d) the conductivity activation energy first decreased from 0.68 to 0.15 eV when the film transition from a- to mu c-Si; then increased slightly with increasing mu c-Si fraction. The results demonstrate that the variation of the H-dilution ratio has significant effects on both the film structures and the optoelectric properties.