An apparatus and process for fast epitaxial deposition of compound semiconductor layers includes a low-energy, high-density plasma generating apparatus for plasma enhanced vapor phase epitaxy. The process provides in one step, combining one or more metal vapors with gases of non-metallic elements in a deposition chamber. Then highly activating the gases in the presence of a dense, low-energy plasma. Concurrently reacting the metal vapor with the highly activated gases and depositing the reaction product on a heated substrate in communication with a support immersed in the plasma, to form a semiconductor layer on the substrate. The process is carbon-free and especially suited for epitaxial growth of nitride semiconductors at growth rates up to 10 nm/s and substrate temperatures below 1000°C on large-area silicon substrates. The process requires neither carbon-containing gases nor gases releasing hydrogen, and in the absence of toxic carrier or reagent gases, is environment friendly.