Intrinsic hydrogenated amorphous silicon (a-Si:H) has been deposited using a hot tungsten filament in pure silane to drive the deposition chemistry—the “hot-wire” deposition method. The electronic and infrared properties of the film have been measured as a function of deposition parameters, leading to three principal conclusions. First, to obtain a high quality material, the Si atoms evaporated from the filament (distanceLfrom the substrate) must react with silane (densityns) before reaching the substrate; this requiresnsLgreater than a critical value. Second, radical-radical reactions cause deterioration of film properties at high values ofG(nsL),3whereGis the film growth rate; this requiresG(nsL)3less than a critical value. Finally, the film quality is a function ofG,and asGis increased the substrate temperature must be correspondingly increased to obtain high film quality. By optimizing these parameters, we have produced films with excellent electronic properties (e.g., ambipolar diffusion length >200 nm) at >5 nm/s deposition rate. Based on these insights, formulas are also given for optimizing film properties in multiple-filament geometries and in diluted silane. ©1997 American Institute of Physics.