A new technique for semiconductor epitaxy at low substrate temperatures is presented, called low-energy de plasma enhanced chemical vapor deposition. The method has been applied to Si homoepitaxy at substrate temperatures between 400 and 600 degrees C and growth rates between 0.1 and 1 nm/s, using silane as the reactive gas. The quality of the Si films has been examined by reflection high-energy electron diffraction, scanning tunneling microscopy, cross-section transmission electron microscopy, and high-resolution x-ray diffraction. Two effects have been identified to lead to the formation of stacking faults after an initial layer of defect-free growth : (1) substrate bombardment by ions with energies in excess of 15 eV, and (2) hydrogen adsorption limiting the surface mobility of Si atoms and silane radicals. Both result in the accumulation of surface roughness, facilitating the nucleation of stacking faults when the roughness reaches a critical level. Defect introduction can be eliminated effectively by biasing the substrate during growth and by decreasing the hydrogen coverage, either by admiring small amounts of germane to the silane or by using a sufficiently high plasma density.