Effects of free electrons and quantum confinement in ultrathin ZnO films : a comparison between undoped and Al-doped ZnO
Li, X. D.
Leong, K. C.
Date of Issue2013
School of Electrical and Electronic Engineering
Band gaps and exciton binding energies of undoped and Al-doped ZnO thin films were determined from optical absorption measurement based on the Elliott’s exciton absorption theory. As compared to the undoped films, the doped films exhibit a band gap expansion and a reduction in the exciton binding energies due to the free electron screening effect, which suppresses the excitonic absorption and results in a blue shift of the absorption edge. The undoped and doped films show the same quantum size dependence, i.e. both the exciton binding energies and band gap energies increase with decreasing grain size of the oxides.
DRNTU::Engineering::Electrical and electronic engineering
© 2013 Optical Society of America. This paper was published in Optics Express and is made available as an electronic reprint (preprint) with permission of Optical Society of America. The paper can be found at the following official DOI: [http://dx.doi.org/10.1364/OE.21.014131]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.