The calculated strain is -0.0054 for sample A and -0.0023 for sample B. Increasing the thickness of InSb-like IF layers can reduce the average compression strain. We predicted one-period thickness from the spacing between the satellites. Each period thickness of sample A is 55.9 Å and 56.8 Å for sample B. Figure 2a,b shows the real parts of the relative reflectance difference measured at 300 and 80 K, respectively. The resonances of two samples have the same lineshape. In the spectra, the sharp peak near 2.05 eV(CP1), which is related to
E 1energy of GaSb. The lineshape of real part is almost the derivative of the GANT61 imaginary part. A small feature is observed at this region, which is coincidence that the InAs E 1 and GaSb E 1+Δ 1energies are both near 2.50 eV(CP2). The InAs Transmembrane Transporters inhibitor E 1energy is a little larger than GaSb E 1+Δ 1 energy. Another feature is observed near 2.78 eV(CP3) corresponding to the critical point energy of InAs E 1+Δ 1. Two shoulder-like features were marked in Figure 2b ABT-888 chemical structure on both sides of the sharp peak near 2.05 eV, which may be attributed to InSb-like IFs. The energy positions are near the E 1 and E 1+Δ 1energies of bulk InSb, and it is more clearly shown in the 80-K measurement.
However, the IPOA structures about GaAs are not observed. In comparison with sample A, it is observed SDHB that GaSb E 1 and InAs E 1+Δ 1features show red shift for sample B, which attributes to the compensation of stress by increasing the thickness of InSb-like IF layer. It is anomalous that a blue shift peak is corresponding to InAs E 1 and GaSb E 1+Δ 1. D. Behr et al. reported that it is complicated by inhomogeneity for E 1 and transition of InAs and E 1+Δ 1 of GaSb [14]. Figure 2 Real part of RD spectra of samples A and B measured at 300 and 80 K. (a) At 300 K. (b) At 80 K. The arrows indicate the CP energies. For SL sample, reflectivity can be described by a three-phase model: (4) with (5) where the indices i and j take the value 1, 2, and 3 for the substrate, SL layer,
and air, respectively. is complex refractive index of the ith layer, d 2is the thickness of the SL layer, Λ is the wavelength of light in vacuum [15]. SL layer are treated as uniaxial medium, is the weighted average refractive index of 100 periods of InAs (10 ML)/GaSb (8 ML) SL layer. We chose a simple three-phase model, with no capping layer: (6) ε s is the dielectric function of GaSb substrate, d is the thickness of the superlattice, and Λ is the wavelength of light [16]. The ε s data of GaSb substrate is taken from Aspnes’ measurement [17]. Figure 3a,b shows the real and imaginary parts of anisotropy dielectric function Δ ε by Equation 5, respectively. The peaks and valleys in the imaginary anisotropic dielectric function spectra are corresponding to the CP energies.