Comparison of microstructure and surface passivation quality of intrinsic a-Si:H films deposited by remote plasma chemical vapor deposition using argon and helium plasma

We have prepared intrinsic hydrogenated amorphous silicon (a-Si:H) films by remote plasma chemical vapor deposition (RPCVD) using Ar and He plasma excitations. The microstructure and effective surface passivation quality of the films are characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and photoconductance decay (PCD). Our preliminary results show that films deposited with He plasma have significantly higher mono-hydride and lower di-hydride content compared with Ar films at similar deposition conditions, however PCD measurements show the effective passivation quality of these films to be comparable. Furthermore, a correlation between He flow rate, the microstructure, and surface passivation quality was found resulting in the enhancement of the effective minority carrier lifetime by 64%, from 1.1 ms (flow rate 520 sccm) to 1.9 ms (flow rate = 208 sccm).