The present disclosure generally relates to gas inject apparatus for a process chamber for processing of semiconductor substrates. The gas inject apparatus include one or more gas injectors which are configured to be coupled to the process chamber. Each of the gas injectors are configured to receive a process gas and distribute the process gas across one or more gas outlets. The gas injectors include a plurality of pathways, a fin array, and a baffle array. The gas injectors are individually heated. A gas mixture assembly is also utilized to control the concentration of process gases flown into a process volume from each of the gas injectors. The gas mixture assembly enables the concentration as well as the flow rate of the process gases to be controlled.