Study of microstructure and defects in hydrogenated microcrystalline silicon films

Microcrystalline silicon films were deposited by very high frequency (VHF) plasma-enhanced chemical vapor deposition (PECVD) with different hydrogen dilution. The microstructure of these films was investigated using Raman spectroscopy and infrared absorption (IR) spectra. The crystalline, amorphous, and grain boundary volume fractions X
_c
, X
_a
and X
_gb
were estimated from Raman measurements. An interface structure factor (R
_if
) is proposed to characterize the grain boundary volume fractions in IR spectroscopy. The density of states (DOS) of the microcrystalline crystalline silicon films were studied by phase-shift analysis of modulated photocurrent (MPC) and photoconductivity spectroscopy. It was observed that DOS increases with increasing grain boundary volume fractions, while the values of electron mobility-lifetime product ¿
_e
T
_e
decease.