The invention relates to methods for the chemical application of coatings by the decay of gaseous compounds, in particular to methods for injecting gases into a reaction chamber. The invention also relates to means for feeding gases into a reaction chamber, said means providing for the regulation of streams of reactive gases, and ensures the possibility of obtaining multi-layer epitaxial structures having set parameters and based on nitrides of group III metals while simultaneously increasing the productivity and cost-effectiveness of the process of the epitaxial growth thereof. Before being fed into a reactor, all of the gas streams are sent to a mixing chamber connected to the reactor, and are then fed into the reactor via a flux former under laminar flow conditions. The mixing chamber and the flux former are equipped with means for maintaining a set temperature. As a result of these solutions, a gaseous mixture with set parameters is fed into the reactor, and the formation of vortices is simultaneously prevented. The maximum allowable volume of the mixing chamber is chosen to take into account the process parameters and the required rarity of heterojunctions.