Photonic crystals provide unprecedented control over light emission, absorption and propagation, which has led to the proposal of a large variety of optoelectronic devices. Three-dimensional devices with electronic functionality have however remained elusive, as fabrication of three-dimensional, electrically active nanostructured materials remains complex. Numerous techniques have been demonstrated to fabricate 3D photonic and plasmonic crystals, including colloidal crystallization, phase mask and multibeam interference lithography, direct laser writing, photolithography, and wafer bonding, but, most of these techniques result in amorphous or polycrystalline material which does not possess the required electronic properties for application in optoelectronics. In this work we demonstrate a method of forming 3D photonic and plasmonic crystals from single crystal III-V semiconductors by metal-organic vapor phase epitaxy (MOVPE). We employ a templatebased fabrication method and grow semiconductor material to fill the structure using a form of selective area epitaxy. The epitaxial growth process (originating at the substrate, in contrast to conformal growth) is much the same as the growth of planar III-V devices in that light emitting layers (e.g. quantum wells), cladding layers, electrically doped layers, etc may all be grown in a single process. Thus, the layers of an optoelectronic device may be defined by the MOVPE growth parameters while the photonic crystal structure is simultaneously imparted to the material using the 3D template. To demonstrate the potential of this technique we have fabricated vertically emitting LED's with embedded InGaAs QW's. The fundamental behaviors of this growth technique will be discussed, including prevention of polycrystalline nucleation, doping, and steps for fabrication of light-emitting heterostructures.