Optical properties of AlN thin films correlated with sputtering conditions

Optical measurements (spectrophotometry in the range 0.2-25 mu m and spectr oscopic ellipsometry in the range 0.35-0.9 mu m) have been performed on AIN thin films of varying thicknesses (0.07-0.7 mu m) using two different sput tering methods. Since aluminium nitride has a semi-conducting behaviour, ab sorption, due to direct and indirect transitions, it is observed in the UV range and the band gap can thus be determined. In the visible range; the ab sorption is very low and the Sellmeier formula provides a correct descripti on of the real part of the complex index. In the middle infrared range, opt ical properties are dominated by phonon behaviour, and the measurements an well described by a two oscillator simulation. (C) 1998 Elsevier Science S. A. All rights reserved.