Dielectric function of wurtizite GaN and AlN thin films

Measurements and calculations of the dielectric function of wurtzite GaN and AIN are presented. Spectroscopic ellipsometry was used to determine epsilon(omega) Of thin film samples in the energy range from 3 to 9.8 eV. Calculations of epsilon(omega) for the bulk materials were performed within a first-principles electronic structure scheme that includes the electron-hole interaction. The agreement between experiment and theory is dramatically improved over the previous work, a result of improvements in both experimental technique and theoretical description. The predicted polarization dependence of the dielectric function of these materials exhibits features similar to that in other wurtzite structure materials. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.