Investigations on optical properties of InAs_0.96Sb_0.04 infrared thin films

InAs_0.96Sb_0.04 infrared thin films were grown by liquid phase epitaxy on n-type (100) InAs substrate by using horizontally sliding multi-wells graphite boats. The dielectric function ε(E) was measured by using spectroscopic ellipsometry at room temperature within 1.5-5.5 eV. Based on the theory of the electronic interband transition and joint state density, the ε(E) spectra were analyzed by S. Adachi's MDF model and the individual contribution from each critical point (CP) was also calculated. The results show that excellent agreement between the model calculation and the experimental data is achieved over the entire energy range studied. E₁ and E₁ + Δ_s transitions are assigned to M₁-type Λ₅^v→ Λ₆^c (or L_4.5^v→L₆^c) and Λ₆^v→ Λ₆^c (or L₆^v→L₆^c), respectively, which are along the Λ symmetry axis (or near the L point) in the first Brillouin zone (BZ). E₂ transition, which is due to the degenerate of M₁-type and M₂-type CPs, is expected to take place along ∑ or Δ axis.