Correlation Between Optical, Morphological, and Compositional Properties of Aluminum Nitride Thin Films by Pulsed Laser Deposition

Aluminum nitride (AlN) thin films were grown in a N-2 atmosphere onto a Si/Si3N4 substrate by pulsed laser ablation. We have varied the substrate temperature for the thin film growth, using X-ray reflectometry analysis, we have characterized the thickness and density of the thin layer and the interface roughness from the X-ray reflectivity profiles. Experimental data showed that the root-mean-square roughness was in the range of 0.3 nm. The X-ray photoelectron spectroscopy (XPS) was employed to characterize the chemical composition of the films. These measurements detected carbon and oxygen contamination at the surface. In the high-resolution XPS Al(2)p data, binding energies for Al-N and Al-O species were identified but no Al-Al species were present. In the N1s data, N-O species were not detected, but chemically bonded O was present in the films as Al-O species. Furthermore, the value of optical energy gap, E-g was similar to 5.3 (+/- 0.1) eV. The composition varied with process conditions, and the nitrogen content decreased in AlN films processed above 500 degrees C.