Embodiments described herein generally relate to apparatus for fabricating semiconductor devices. A gas injection apparatus is coupled to a first gas source and a second gas source. Gases from the first gas source and second gas source may remain separated until the gases enter a process volume in a process chamber. A coolant is flowed through a channel in the gas injection apparatus to cool the first gas and the second gas in the gas injection apparatus. The coolant functions to prevent thermal decomposition of the gases by mitigating the influence of thermal radiation from the process chamber. In one embodiment, the channel surrounds a first conduit with the first gas and a second conduit with the second gas.