I measured transmission curve for a semiconductor thin film, it shows a slightly decreasing behavior from 600 nm to 850 nm wavelength. Is this due to the presence of defect states present in the thin film or any other reason?
Very possibly, however you should investigate the matter further. The colour centres F, M and R [1,2] correspond to relatively narrow absorption peaks. Therefore, look at the transmission over a wider frequency range, even though the interval 600-850nm seems narrow enough.
[1] NW Ashcroft, and ND Mermin, Solid State Physics (Thompson Learning, Australia, 1976), pp. 622-626.
[2] RJD Tilley, Defects in Solids (John Wiley & Sons, Hoboken, NJ, 2008).
Dear Muhmmad ,
welcome,
Adding to the above answer, decreased transmission means increased reflection coefficient or increased absorption. The increase absorption may be due to increased scattering on the material defects. You may need more investigations t determine the specific cause of the decreased transmission in the given wavelength range. In general optical absorption depends strongly on the energy band structure.
Best wishes
In addition to what was said above, it could also be the effect of interference fringes. Could you provide the spectrum?
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