Abstract
This work investigates the temperature dependence of electron states at the band-edge
in ZnO and Mg0.07Zn0.93O thin films.
To investigate the band-edge dynamics, we study in-gap states via temperature
dependent absorption spectroscopy in the range 77-500K. The in-gap states at the
band-edge were analyzed via the Urbach energy model, where the Urbach Energy is
a measure of the extent of states into the bandgap. In parallel, we also analyze the
temperature dependent Urbach energy via the Wasim model, which separates the
relative contributions of defect states and temperature dependent phonon modes to
the in-gap states.
It was found that the defect contribution to in-gap states at the band-edge
was significantly higher for Mg0.07Zn0.93O than in ZnO. Additionally, the phonon
contribution to in-gap states was less in Mg0.07Zn0.93O than in ZnO.
The author gratefully acknowledges the National Science Foundation and the U.S.
Department of Energy, Office of Basic Energy Science, Division of Materials Science
and Engineering under Grant No. DE-FG02-07ER46386.