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[摘要]：This paper reports on the optical and transport properties of undoped and In-doped CdO films prepared by pulsed laser deposition. Film thickness (around 150 nm) was chosen to allow for an accurate measurement of the absorption coefficient spectrum up to 2-3 eV above the direct bandgap. The imaginary part of the dielectric function, as determined from absorption spectra, is consistent with ellipsometry results in the literature. The optical gap and transition width are determined from a gaussian fit to the first derivative of the absorption spectrum. CdO optical gap so determined increases from 2.3 to 3.4 eV for electron concentrations increasing from 1.8 x 10(19) to 1.1 x 10(21) cm(-3) with a Burstein-Moss shift of 1.1 eV, much larger than those currently found in the literature for similar or larger carrier concentration ranges. We discuss this discrepancy and show that the origin of the current underestimation is related to an extended misuse of alpha(2)-versus-h nu plots to determine the optical gap. A clear correlation between the optical transition width and electron mobility is also shown and discussed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3651338] |
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