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Measurements of optical properties of bulk and thin film semiconductors using the PDS technique Elouneg-Jamroz, Miryam

Abstract

Photothermal deflection spectroscopy (PDS) was used to measure the bandgap optical parameters and the Urbach energy of semi-insulating (SI) GaAs and a 238nm GaNAs epitaxial thin film in the energy range 800-1l00nm. To do so, a PDS apparatus was setup using a 0.lmW and l0nm bandwidth pump beam obtained with a f/3.8 monochromator and a 150W Tungsten Halogen lamp, a HeNe laser for the probe beam, CCI[superscript omitted] for the deflecting medium and a linear position sensitive detector. The spectra obtained for GaAs and GaNAs were compared with models based on the Rosencwaig-Gersho and the Fernelius theories of ID heat diffusion which consider absorption in respectively one and two sample layers, and also on a model of absorption based on literature results. Preliminary results indicate that more work will be needed on the apparatus/models to qualify the validity of the fitted optical parameters. The PDS apparatus demonstrated an absorbance sensitivity limit of ~10[superscript omitted] with the samples investigated.

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