Abstract: An apparatus for depositing a group III metal nitride film on a substrate, the apparatus comprising a plasma generator to generate a nitrogen plasma from a nitrogen source, 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, a plasma inlet to facilitate the passage of nitrogen plasma from the plasma generator into the reaction chamber and a baffle having one or more flow channels for passage of the nitrogen plasma. The baffle is located between the plasma inlet and the substrate and prevents a direct line of passage for nitrogen plasma between the plasma inlet and the substrate.