Analysis of free-carrier optical absorption used for characterization of microcrystalline silicon films

The analysis of free-carrier optical absorption was applied to investigation of electrical properties for doped microcrystalline silicon films formed at 100–180°C by the RF-plasma-enhanced chemical vapor deposition method. The analysis gave in-depth characteristics of the carrier mobility and the carrier density. The electron mobility was 8 cm2/Vs (phosphorous doped) and 6 cm2/Vs (boron doped) at the surface region and it decreased to ∼1 cm2/Vs at bottom film/substrate interfaces. The carrier mobility and density were much higher than those obtained by Hall effect current measurements. It shows the existence of substantial non-activated and disordered regions among crystalline grains.