Effect of the Nitrogen Incorporation on the Microstructure and Photoelectric Properties of N Type Nanocrystalline Silicon Thin Films.

N type silicon-rich nanocrystalline-SiN(x) ∶ H films were prepared by plasma enhanced chemical vapor deposition technique by changing NH3 flow rate. The effect of nitrogen incorporation on the microstructure and photoelectric properties of the thin films were characterized by Raman, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectra, and Hall effect measurement. The results indicated that with the increasing NH3, a phase transition from microcrystalline to amorphous silicon occured. Transmission electron microscope observation revealed that the size of silicon quantum dots could be adjusted by varying the flow rate of NH3. The microstructure order of the films reduced with increasing the flow rate of NH3, while the optical band gap increased, and the optical band tail became narrow. Meanwhile, Si—N bonds density increased and P doping was blocked. I-V testing results showed that with increasing NH3, the conductivity of films first decreased compared with nanocrystalline-Si and then increased. These behaviors reveal a competition in the mechanisms controlling the conductivity. However, with further increasing NH3, the conductivity decreased significantly due to rapid carrier recombination on the amorphous net structure.