An injector block for supplying one or more reactant gases into a chemical vapor deposition reactor. The injector block including a plurality of first reactant gas distribution channels between one or more first reactant gas inlets and a plurality of first reactant gas distribution outlets to deliver a first reactant gas into the reactor, and a plurality of second reactant gas distribution channels between one or more second reactant gas inlets and a plurality of second reactant gas distribution outlets to deliver a second reactant gas into the reactor, the plurality of second reactant gas distribution outlets partitioned into at least a second reactant gas first zone and a second reactant gas second zone, the second reactant gas second zone at least partially surrounding the second reactant gas first zone.