Film structure dependence of electrical properties of microcrystalline silicon

Microcrystalline silicon thin films were prepared by the hydrogen radical CVD method. The surface roughness and maximum projection size were measured by ultraviolet reflectance spectra. Electrical conductivities in lateral and vertical directions were estimated as average value for film thickness. The lateral dark conductivity of microcrystalline silicon showed a low value about 10(-7) S/cm in film thickness blow 200 nm. However, it was saturated in about 5 x 10(-4) S/cm as film became thick. On the other hand, the vertical dark conductivity showed 10(-11) similar to 10(-9) S/cm. The structural and electrical properties of initial growth layer were examined using films 200 nm thick prepared by changing hydrogen dilution ratio. In the transition region from amorphous to crystalline. a characteristic change of electrical conductivity was observed.