Near-bandgap infrared absorption properties of HgCdTe

We report temperature-dependent absorption measurements from 300 K to 4.2 K for molecular beam epitaxy (MBE)-grown Hg1−xCdxTe samples with different alloy compositions. The infrared absorption coefficients near the energy gap were obtained using an interference matrix method. Photoconductive spectra were simultaneously measured at the same points on the samples to precisely determine the energy gaps. The Urbach tail energies are extracted from the absorption coefficients, and their temperature dependence is analyzed using a theoretical model. The contribution from static disorder, including structural and alloy disorder, is found to be much larger than the phonon-related dynamic disorder.

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