Infrared spectroscopic data are correlated here together with conductivity results, transient photoconductivity measurements and fundamental absorption data in an attempt to understand the physical processes involved in the growth of tungsten hot-wire deposited hydrogenated amorphous silicon. Film surface growth processes initially involve diffusing thermally dissociated radicals, with a subsequent additional contribution from evaporated silicon species. We show how changing processes at the heated wire surface, surrounded by silane gas, affect the electronic and structural properties of the hydrogenated amorphous silicon produced. Depth profiling by chemical etching reveals substantial variations in the level of contamination and in the electronic structure throughout the film.