Cyclohexasilane is used in chemical vapor deposition methods to deposit epitaxial silicon-containing films over substrates. Such methods are useful in semiconductor manufacturing to provide a variety of advantages, including uniform deposition over heterogeneous surfaces, high deposition rates, and higher manufacturing productivity. Furthermore, the crystalline Si may be in situ doped to contain relatively high levels of substitutional carbon by carrying out the deposition at a relatively high flow rate using cyclohexasilane as a silicon source and a carbon-containing gas such as dodecalmethylcyclohexasilane or tetramethyldisilane under modified CVD conditions.