The effect of hydrogen species on the electronic properties of nc-Si:H prepared in a triode PECVD system

The effect of hydrogen species on the microstructures and the electronic properties of nanometer sized crystalline silicon (nc-Si:H) prepared in a triode plasma-enhanced chemical vapor deposition (PECVD) system with a hydrogen-diluted silane plasma were investigated. It has been found that for a given set of deposition parameters there is a threshold value of dilution ratio (H-2/H-2 + SiH4) for the formation of nc-Si:H, which suggests that a minimum concentration of hydrogen atoms should be provided at the growing surface during the deposition processes. The electronic properties of nc-Si:H were changed when the H-2 dilution ratio was greater than 94%. The dark-conductivity, sigma(d), increased from 10(-10) to 10(-3) S/cm, although the photo-conductivity, sigma(ph), changed by only one order of magnitude. In addition, the drift mobility, mu(d), increased from 0.8 to 16 cm(2)/V . s. The dependence of the electronic properties on the hydrogen content and structural configurations;in nc-Si:H is briefly discussed.