The subject invention pertains to a method and device for producing large area single crystalline III-V nitride compound semiconductor substrates with a composition AlxInyGa1-x-y N (where 0≦x≦1, 0≦y≦1, and 0≦x+y≦1). In a specific embodiment, GaN substrates, with low dislocation densities (˜107 cm2) can be produced. These crystalline III-V substrates can be used to fabricate lasers and transistors. Large area free standing single crystals of III-V compounds, for example GaN, can be produced in accordance with the subject invention. By utilizing the rapid growth rates afforded by hydride vapor phase epitaxy (HVPE) and growing on lattice matching orthorhombic structure oxide substrates, good quality III-V crystals can be grown. Examples of oxide substrates include LiGaO2, LiAlO2, MgAlScO4, Al2MgO4, and LiNdO2. The subject invention relates to a method and apparatus, for the deposition of III-V compounds, which can alternate between MOVPE and HVPE, combining the advantages of both. In particular, the subject hybrid reactor can go back and forth between MOVPE and HVPE in situ so that the substrate does not have to be transported between reactor apparatus and, therefore, cooled between the performance of different growth techniques.