Fabrication of high-quality surface microtextures on GaN by femtosecond laser direct writing

Gallium nitride (GaN), as a third-generation semiconductor, is highly attractive due to its exceptional physical and chemical properties. Laser direct writing offers an efficient method for the precise processing of hard and brittle materials. In this work, various types of surface microtexture were processed on GaN epilayers using a femtosecond laser with a wavelength of 1030 nm. The effects of the laser energy, single-pulse interval, number of pulses, and number of scan passes on groove machining were investigated with a view to achieving high-quality micromachining. The depth, width, surface morphology, and roughness of the grooves were analyzed using scanning electron microscopy, laser scanning confocal microscopy, and atomic force microscopy. Damage and stress were characterized at the microscale using Raman spectroscopy. High-quality precision machining of different types of periodic surface microtexture at 40 mW laser power was achieved by controlling the process parameters and laser trajectory. Finally, an initial exploration was conducted to examine vector-light-based micro- and nanostructure processing. The findings demonstrate the potential of femtosecond lasers for efficient micromachining of hard and brittle materials without the creation of heat-affected zones or microcracks. The high-quality textured structures achieved through this processing technique have broad and promising applications in optoelectronic devices and tribology.