engleski

On the evaluation of optical parameters of a thin semiconductor film from transmission spectra, and application to GaN films

The analysis of the optical transmission spectra of semiconductor thin films on a transparent substrate is revisited. The equation for the optical transmission is re-derived and applied for the evaluation of optical parameters. A method based on the pace of the interference pattern is analyzed in detail. It can be used for the determination of the film-thickness, refractive index and absorption coefficient. Small values of the absorption coefficient can be determined as a fitting parameter at all wavelengths, regardless of strong interference. The method is compared to the frequently encountered envelope-method of Manifacier et al. and Swanepoel. The suitability of the method is illustrated on two GaN thin films grown on sapphire. Below the band-gap, the index of refraction of GaN can be described by the equation n(lamda[nm])=2.19+2.57(lamda-345)^( 1/2).

thin films ; semiconductors ; optical transmission

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