Extracting the complex refractive index of an ultrathin layer at terahertz frequencies with no prior knowledge of substrate absorption loss

A method based on complementary transmission and reflection measurements is developed to determine the complex refractive index of an ultrathin layer, despite no knowledge of the substrates absorption loss. Such a technique avoids error introduced by conventional methods in which the extinction coef...

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Bibliographic Details
Published in:IEEE transactions on terahertz science and technology 2022-07, Vol.12 (4), p.1-1
Main Authors: Carnio, Brett N, Attiaoui, Anis, Assali, Simone, Moutanabbir, Oussama, Elezzabi, Abdulhakem Y
Format: Article
Language:English
Subjects:
Absorption
Electric fields
Fresnel equations
germanium tin
Loss measurement
Mathematical models
numerical modelling
Reflection
Refractive index
Refractivity
Silicon
Substrates
Terahertz frequencies
Terahertz time-domain spectroscopy
Thin films
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Summary:A method based on complementary transmission and reflection measurements is developed to determine the complex refractive index of an ultrathin layer, despite no knowledge of the substrates absorption loss. Such a technique avoids error introduced by conventional methods in which the extinction coefficient of the substrate is extracted from a different region of the wafer, or an entirely different sister wafer. This method is implemented to determine the terahertz complex refractive index of highly doped (i.e. >1018 cm-3) thin films from the emerging group IV semiconductor of GeSn, as well as the terahertz extinction coefficient of the underlying substrate region.
ISSN:2156-342X
2156-3446
DOI:10.1109/TTHZ.2021.3140196