Optical properties of narrow-gap semiconductors have been widely investigated. The absorption at the band edge is essential to determine the performance of IR photodetectors. However, there still appears to be considerable disagreement among the reported results concerning absorption coefficients at wavelengths close to those corresponding with the bandgap. In most compound semiconductors, the band structure closely resembles the parabolic energy versus the momentum dispersion relation. The optical absorption coefficient would then have a square-root dependence on energy that follows the electronic density of states, often referred to as the Kane model. The above bandgap absorption coefficient can be calculated for InSb-like band structure semiconductors such as Hg1âxCdxTe, including the Moss-Burstein shift effect. Corresponding expressions were derived by Anderson.
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