UV-VUV spectroscopic ellipsometry of ternary MgxZn1-xO (0 <= x <= 0.53) thin films

The ordinary optical dielectric functions of pulsed-laser-deposition grown wurtzite c-plane MgxZn1yxO (0FxF0.53) thin films have been determined by using spectroscopic ellipsometry in the photon energy range from 4.5 to 9.5 eV. The dielectric functions reveal features which resemble those previously detected in uniaxial AlGaN and identified as E1- and E2-type band-to-band transitions with no remarkable dependence of the transition energy on Mg content x. The E1- and E2-type transitions for ZnO are compared with pseudopotential band-structure calculations.