Free Carrier Absorption in n‐Type Indium Selenide

Abstract
Infrared absorption of n‐type indium selenide is studied in the 2.5 to 50 μm spectral range at 300 °K. Lattice absorption peaks are observed between 25 and 50 μm. Tin‐doped samples with an electron concentration higher than 1016 cm−3 exhibit free carrier absorption for λ larger than 10 μm. The experimental results are interpreted by the quantum theory of free carrier absorption. Quantitative account of absorption coefficients is given by introducing homopolar optic phonon and ionized impurity scattering.