Terahertz characterization of semiconductor alloy AlInN: negative imaginary conductivity and its meaning: comment.

In a recent article [Opt. Lett.34, 2507 (2009)], the authors concluded that the imaginary part of the complex conductivity sigma of an AlInN film was negative. However, this result was obtained using an approximation that is not applicable in this case. Using the correct equation, the data can be well described with a positive imaginary part of sigma.