Low refractive cladding in III-nitride photonics

III-Nitride based photonic crystals or metamaterials can operate in the visible and ultraviolet frequencies and are important for many nanophotonics applications. A key challenge in efficient operation of such III-nitride based optical nanostructures has been in creating a low refractive index interface cladding region between the high refractive index substrate GaN and the active layer due to a lack of compatible natural low index materials unlike those in Si and III-V systems. Here we will discuss achieving such optical substrate isolation in III-nitride nanophotonic devices using electrochemical and photo-electrochemical etching techniques [Opt. Mat. Exp. 2018, 8, 3543]. We will describe the fabrication of a GaN nanowire array utilizing this method of optical isolation and present the optical response to demonstrate the effectiveness of this approach. Sandia National Laboratories is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.