engleski

Determination of the optical parameters of semiconductor thin films from optical transmission

The optical transmission spectra are frequently used for the characterization of thin semiconductor films for the determination of the film's thickness, the refractive index, the absorption coefficient and the energy band gap (Eg) of a semiconductor. For that purpose the methods of Manifacier, et all, and particularly of Swanepoel are frequently used in the literature. Here, we reexamine these methods. A probable inaccuracy in Swanepoel 's formula for the transmission is analyzed and pertinent corrections are introduced. Further, both methods use the interference maxima and minima for the evaluation of the refractive index n(lamda). As an alternative, we examine the determination of n(lamda) from the pace of the interference patterns. Further, we propose the use of the substrate’ s transmittance as the base line signal (Io). This is useful for the samples grown on substrates with the unpolished backside as well as for the spectral range in which the absorption of the substrate is not negligible.

thin films; optical transmission; refractive index; semiconductors

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