Laser-induced damage threshold and surface processing of GaN at 400 nm wavelength

The laser-induced damage of epitaxially grown GaN semiconductor material is investigated for the first time by illumination of the c-plane by sub-pico second laser pulses at the wavelength of 400 nm. The surface damage was inv estigated by optical and atomic force microscopies. The threshold fluence f or ablation damage is determined to be similar to 5.4 J/cm(2) for pulse wid th of 150 fs. An application is demonstrated for laser-beam processing by t he formation of clean dips on the GaN surface to depths of 240 nm in a sing le shot.