A system for epitaxial deposition of a Group III-V semiconductor material that includes gallium. The system includes sources of the reactants, one of which is a gaseous Group III precursor having one or more gaseous gallium precursors and another of which is a gaseous Group V component, a reaction chamber wherein the reactants combine to deposit Group III-V semiconductor material, and one or more heating structures for heating the gaseous Group III precursors prior to reacting to a temperature to decompose substantially all dimers, trimers or other molecular variations of such precursors into their monomer forms.