This project will focus on understanding plasma-induced damage at the sidewalls of micro-nano-patterned III-V semiconductors to find relevant technological solutions capable to minimize this damage. There is a clear need of knowledge on by which mechanisms and to what extent the plasma etching process modifies the III-V pattern sidewalls and the consequences it has on the device optical performances. The selected III-V semiconductor will be aluminium gallium arsenide which exhibits excellent optoelectronic properties and strong nonlinear parametric gain. The student will be mainly focused on understanding how the key plasma process parameters influence the structural and chemical changes at the III-V sidewalls, as well as changes of optical properties. This will require the development of a methodology for a 3D quantitative characterization of the sidewalls at the nanoscale, based on Auger microscopy and cathololuminescence. The main objective will be to correlate plasma-induced structural defects and modifications of the optoelectronics properties. The second step will consist in developing optimized plasma etching processes for III-V semiconductors, exploring alternative plasma technologies. You will also be involved in the development of processes for restoring and passivating the AlGaAs sidewalls.