Investigation of intrinsic defect states in hydrogenated amorphous silicon films using steady-state photoconductivity and sub-bandgap absorption

The density, distribution and nature of intrinsic gap states in a-Si:H films deposited over a wide range of substrate temperatures have been investigated using steady-state photoconductivities and sub-bandgap absorption. The sub-bandgap absorption was obtained using dual beam photoconductivity (DBP) measurements and the results were analyzed using a detailed numerical model based on Rose-Simmons-Taylor statistics. This model takes into account the effects of mobility, recombination velocity, position of Fermi level, and the presence of sensitizing states. It is found that there is a large effect of sensitizing states and position of Fermi level on both electron mobility-lifetime products and sub-bandgap photoconductivities used to obtain information about gap states in different films