A photoluminescence study of laser ablated gallium nitride thin films

摘要

Photoluminescence analysis has been implemented to investigate the crystalline properties of Gallium Nitride layers ablated with an XeCl excimer laser. The measurements were carried out on craters up to 1 μm deep, which corresponded to almost half the thickness of the deposited film. The craters were etched in an air environment with laser fluences in the range of 99-231 mJ/cm~2. In the 350-1200 nm spectral range, the near-band-edge emission, and the donor-acceptor pair recombination were identified. All spectra were dominated by the excitonic recombination. The analysis revealed that during the ablation, the full width at half maximum of the donor-bound luminescence line remained almost independent of both the depth of the crater and of the laser fluence. Also, the donor-acceptor pair recombination, which manifests its presence through a weak yellow luminescence observed in the vicinity of the 600 nm wavelength, has been consistently observed in the spectra. A relative decrease in the excitonic emission indicated that a thin layer of altered material with lower crystalline quality was formed at the surface of the ablated material.