New mechanism for incline crystal growth and carrier path transition in extremely highly doped polymorphous silicon thin film formated by neutral beam assisted CVD process near room temperature

摘要

The neutral beam assisted chemical vapor deposition (NBaCVD) system can control the crystalline phase and the doping efficiency simultaneously by the energy of impinge neutral particle beam. During the deposition process, energetic hydrogen (H) neutral atoms transport their energy to the surface of depositing film to enhance crystallization (crystal volume fraction (Xc) up to 85%) and dopant activation (～1×10~(20) #/cm~3, ～30 cm~2/Vs) with low H ratio at near room temperature on the substrate. The increase of H neutral beam flux induces transition of crystal orientation from [111] to [311] at constant Xc and changes the carrier transport path from "grain boundary path" to "grain-to-grain percolation path" and enhances bulk mobility of the Si thin film. The various analysis data of the thin films (XRD, Raman, temperature dependent conductivity, Hall measurement) represent the evidence of very high doping efficiency at near room temperature, obvious nano-crystalline embedded polymorphous phase, and mixed transport (band and percolation) characteristics.