PHOSPHINE DOPING EFFECTS IN THE PLASMA DEPOSITION OF POLYCRYSTALLINE SILICON FILMS

The effects of phosphine doping on the electronic and structural properties of polycrystalline silicon (poly-Si) films prepared by plasma chemical vapour deposition using SiF4/SiH4/H2 gases have been investigated. With increasing doping ratio, the conductivity rapidly increases and takes a maximum value of 80 S . cm-1 at [PH3]/[SiH4](= gamma) approximately 1.7 x 10(-2), while it decreases at larger doping ratios. This change is found to be caused mainly by the change in the carrier density, by Hall measurements. X-ray diffraction and transmission electron microscopy indicate that this electronic change is associated with the change in the preferred orientation of grains from [110] to [111] with a slight decrease in grain size, and the structural change from crystalline to amorphouslike with increasing gamma.