The pyrolysis of silane diluted by a carrier gas in a horizontal‐type system is described. Films of closely controlled thickness have been obtained. Control of the electrical resistivity of the films by admixture of suitable dopants is shown. The effect of various process parameters on growth rate is discussed. Experimental data on migration of dopant from the substrate to the grown layer are presented, and the mechanism involved is discussed. Some characteristics of devices using such layers are shown.