## 3 Optical Characterization  
The photoconductors structures of the grown T2 SLs InAs/InAsSb were processed with standard photolithography technique and wet etching. The intent T2 SLs active layer thickness (\(l\)) was assumed at the level of 3 \(\upmu\)m (Table 1). For Set 1, the number of periods (intentional number) was assumed at the level of 317. For Set 2 (intentional number), the number of periods was assumed at the level of 288. Period (\(P\)) and Sb composition were estimated based on XRD simulation. As presented in Table 1, thickness \(l\) varies within the range of 2.95-3.04 \(\upmu\)m.  
The spectral characteristics were presented by normalized responsivities (\(R_{in}\)) according to the following relation: \(R_{in}=R_{i}\cdot\frac{l}{E}=\frac{\lambda\eta\eta}{\hbar c}\cdot\tau\mu_{e}\), where \(\eta\) is the quantum efficiency, \(q\) is the electron charge, \(l\) is the length between contacts, \(E\) is the electric field, and \(\mu_{e}\) is the electron mobility. \(R_{in}\) enables the determination of responsivity (\(R_{i}\)) normalized versus electric field and device length. The spectrophotometer's incident beam (which was used in experiments) illuminated all active areas of the photoconductor with the same incident power density. That minimized the device's geometry contribution to the \(R_{in}\). Figures 4 and 5 show the spectral characteristic versus temperature and wavelength (\(\lambda\)), respectively. \(\lambda_{50\%\textit{scut-off}}\) correlated strongly versus growth temperature, with a marked redshift at 400 \({}^{\circ}\)C and blueshift at 450 \({}^{\circ}\)C. In addition to the blueshift, Set I samples grown at 450 \({}^{\circ}\)C showed broadening due to higher-order satellite peaks. Only Set I samples 1, 2, and 3 (Figure 4a) did not follow the trend in terms of the \(\lambda_{50\%\textit{scut-off}}\) versus \(T_{growth}\). Figure 4: \(\lambda_{50\%\textit{scut-off}}\) versus \(T_{growth}\) and T2 SLs’ period: (**a**) samples 1, 2, 3; (**b**) samples 4, 5, 6; (**c**) samples 7, 8, 9; (**d**) samples 10, 11, 12. Investigation of the observed behavior was more complicated. The T2 SLs InAs/InAsSb energy bandgap (\(E_{g}\)) is defined as a distance between valence and conduction minibands. The main factors contributing to the location of minibands are strain, InAsSb Sb composition (\(x_{Sb}\)), and T2 SLs period (\(P\)) [16; 17; 18]. According to the measured structure properties, variations in the T2 SLs period and Sb composition were small within each sample and assumed negligible in our analysis. The only interfaces regions within T2 SLs InAs/InAsSb could affect the location of minibands. At the interfaces between InAs and InAsSb, the strain could be changed due to InAsSb Sb composition distribution within InAsSb and InAs layers, which will be discussed later. Our research identified only two papers on the growth temperature influence on the T2 SLs cut-off wavelength. [PERSON] et al. changed the \(T_{growth}\) of T2 SLs InAs/InAsSb from 400 \({}^{\circ}\)C to 450 \({}^{\circ}\)C. Unfortunately, the presented samples prepared for each temperature also differed in period and \(x_{Sb}\), and no direct comparison was possible [19]. The Sb cross-incorporation into InAs layers was observed but also not explained. The same situation could be found in a paper by [PERSON] et al. [20]. The samples were grown in selected temperatures without compensation of the As and Sb beams. The higher growth temperature lowers Sb composition in the InAsSb layer and changes the T2 SL InAs/InAsSb bandgap. The detailed investigation of epitaxial T2 SL InAs/InAsSb was carried out first by [PERSON] et al. and later by [PERSON] et al. [21; 22]. In both papers, the authors measured interfaces of the same sample by scanning tunneling microscope (STM) and scanning transmission electron microscope (STEM), respectively. [PERSON] et al. provided information on the interfaces inside the structure, where Sb segregation was observed and fitted to a standard segregation model formulated by [PERSON] et al. [23].