Effect of Laser Wavelength for Surface Morphology of Aluminum Nitride Thin Films by Nitrogen Radical-Assisted Pulsed Laser Deposition

AlN thin films were prepared on Si(100) substrates by the nitrogen radical-assisted pulsed laser deposition method at a low substrate temperature (200°C) as a function of the laser wavelength (1064, 532 and 266 nm). At the laser wavelength of 1064 nm, Al-rich AlN films were deposited and granular crystals with a diameter of 50 nm were observed on the film surface. The surface roughness (R a) was 15 nm. At the laser wavelength of 266 nm, c-axis-oriented AlN thin films with smooth surfaces (R a=5 nm) were obtained and the atomic ratio of N/Al was stoichiometric. The full width at half maximum (FWHM) value of the diffraction profile in the 2θ/θ scan mode was 0.55°. It was found that the use of an ultraviolet laser was more effective for preparing the c-axis-oriented AlN films with a stoichiometric concentration and smooth surfaces.