Plasma deposition

An apparatus for depositing a group III metal nitride film on a substrate, the apparatus comprising:

• (a) a plasma generator to generate a nitrogen plasma from a nitrogen source;
• (b) a reaction chamber in which to react a reagent comprising a group III metal with a reactive nitrogen species derived from the nitrogen plasma so as to deposit a group III metal nitride on the substrate;
• (c) a plasma inlet to facilitate the passage of nitrogen plasma from the plasma generator into the reaction chamber;
• and
• (d) a baffle having one or more flow channels for passage of the nitrogen plasma, the baffle located between the plasma inlet and the substrate and the baffle comprising a plurality of distribution members located above a blocking member, each distribution member defining an aperture and being spaced from adjacent distribution members and the blocking member, wherein the apertures defined by the distribution members are progressively smaller upon approaching the blocking member, and
• wherein the baffle prevents a straight line of passage for nitrogen plasma between the plasma inlet and the substrate.