Gallium nitride is a wide bandgap semiconductor of huge economic importance, and the subject of the Nobel Prize for Physics in 2014. It is the base material for lasers in Blue-Ray drives, light emitting diodes in solid state lighting and can also offer improvements in performance of field effect transistors at high speed and high power. GaN is hard, inert and biocompatible. It can be alloyed with indium and aluminium to tune emission from 200 to 2000nm, an unprecedented range for any semiconductor, making it a flexible platform for future device manufacturing. In addition, the material stiffness of GaN leads to high frequency and high-mechanical quality-factor oscillators that can be used as inertial sensors of superior performance to the silicon MEMS devices currently used in airbags, motion detectors and aerospace. Applications will benefit from the ability to create 3D structures of high quality. We propose to etch GaN at a steep angle using a novel single-step angled etch process with a Faraday cage. We will create suspended GaN cavities that confine light using the refractive index difference between GaN and air, for applications in photonics, nanoscale lasers and sensors.