Excimer laser induced microstructures on the surface of free standing Gallium Nitride wafers

Gallium Nitride (GaN) is an important semiconductor material as GaN based devices have revolutionised the optoelectronics and high power electronics sectors. A great deal of attention has been focused on developing methods to fabricate semiconductor nanostructures with uniform size distributions. We report the formation of Excimer laser induced periodic surface structures. The ablation threshold of GaN with the 193 nm excimer laser was determined empirically. The surface structures were produced using a phase mask with a 668.2 nm periodicity. The features produced on the surface of the GaN were regular and of uniform periodicity, however, a significant amount of debris was generated during the machining of GaN. In order to try and reduce the debris generated further trials were carried out on both process optimisation and also on the use of a variety of assist gases. It is concluded that fluence does not have a significant impact on debris generation and Helium was found to be the most successful assist gas reducing the debris significantly.