Influence of microstructure on the electrical properties of P-type microcrystalline silicon thin film

P-type microcrystalline silicon (μc-Si:H) thin films with different concentrations of silicane were prepared by RF plasma enhanced chemical vapor deposition (RF-PECVD). The microstructure and energy band structure properties of the μc-Si:H films were characterized by Raman and ultraviolet-visible absorption spectral, while the conductivities were analyzed by conductivity measurement. The results show that as the silicane flow rate increasing, the thin film structure transforms from crystalline silicon to amorphous silicon and the micro-structural order also reduces. In addition, the optical band gap of thin films increases first, and decreases then, and the band-tailed distribution narrows. The measurement of conductivity indicates that the dark conductivity of thin film increases first, and later decreases as a consequence of the influence of both mobility and carrier concentration. It reveals that many competition mechanisms affect the conductivity of thin films. Meanwhile, the conductivity decreases significantly due to rapid carrier recombination on the nanocrystalline silicon grain boundary.