Processing grating structures on surfaces of wide-bandgap semiconductors using femtosecond laser and phase mask

Abstract

Fabrication of grating structures on surfaces of wide-bandgap semiconductors, namely silicon carbide (SiC) and gallium nitride (GaN), was achieved using a femtosecond laser and a phase mask. The phase mask was used to produce stable interference patterns from the focused femtosecond laser to form the grating struc- tures on the bulk materials. The effects of the irradiation power and time on the Bragg grating morphology that was formed on the SiC surface were studied. By optimizing the fabrication parameters, we successfully pro- duced grating structures with uniform periods of 1.07 μm on SiC and GaN. The threshold powers necessary for grating structure formation on wide-bandgap semiconductors were investigated. It was found that the thresh- old powers for SiC and GaN were much smaller than those for silica glass. The reason for this difference is that the absorption of the incident laser light in SiC and GaN is a lower-order nonlinear absorption process compared to that in silica glass. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1.OE.54.12.126106)