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InAs/GaSb type-Ⅱ superlattices (T2SLs) are considered as high-quality material for the third-generation infrared detectors due to the special energy band structure and mature material growth technology. This paper introduces the optical properties of InAs/GaSb T2SLs for long-wave and short-wave infrared detection. The Raman vibration modes in the superlattice detector structure are obtained by Raman spectra at different layers, and the sub-band photoluminescence spectrum reveals that the device has dual band characteristics of near-infrared and far-infrared. The obvious absorption characteristics of short wave infrared and long wave infrared are characterized by reflection spectrum, photocurrent spectrum and wide band infrared transmission spectrum. The detection mechanism in the near, middle and far infrared bands is reasonably interpreted. The investigation can provide reference for the structural design and mechanism analysis of the development of dual/multi/broadband infrared detectors based on InAs/GaSb T2SLs.

InAs0.9Sb0.1-based nBn structures for mid-wave infrared detection are designed and prepared by molecular beam epitaxy. The structural, electrical, and optical properties are characterized, based on which the density-functional theory calculation is carried out by combining with the hybrid HSE06 exchange-correlation function. The results demonstrate that (i) the calculated bandgap for InAs0.9Sb0.1 is well consistent with that of optical spectroscopies (∼266 meV, or a cutoff wavelength of ∼4.66 μm), suggesting the practical effectivity of the theoretical model; (ii) the valence band offset of the unbiased InAs0.9Sb0.1/AlAs0.1Sb0.9 nBn structure is determined as ∼105 meV, with ignorable influence on the hole transport of the devices by considering the rather low dark current when working at a high temperature of ∼150 K; and (iii) the conduction band offset of InAs0.9Sb0.1/GaSb is roughly ∼0.6 eV. This work not only provides a strategy for effectively evaluating the InAs1−xSbx bandgap both theoretically and experimentally but also offers a more reliable basis for fabricating high-performance mid-infrared detectors with high operating temperatures. [ABSTRACT FROM AUTHOR]

Layered van der Waals (vdw) materials have been proposed as light-absorbing materials for photovoltaic applications. InSe is a layered vdw semiconductor with ultra-high carrier mobility, strong charge transfer ability, super deformability, thermoelectricity, and optoelectronic properties. Its γ phase, or γ-InSe, was greatly stabilized by doping recently, which also exhibits sliding ferroelectricity. In this study, we propose that γ-phase InSe (γ-InSe), which was recently synthesized in a high-quality bulk phase, could be an excellent light-absorbing material candidate. Based on the first-principles simulations, bulk γ-InSe is found to possess suitable bandgap, decent absorption, and low effective mass. The investigation of defect properties reveals the major defect types, defect levels, and deep-level defects that could possibly harm the efficiency, and the deep-level defects can be significantly suppressed under Se-rich conditions. In addition, γ-InSe is intrinsically n-type, which can be tuned into weak p-type by Zn and Cd doping. We also identify the defect types of Y and Bi doping, which have been experimentally used to adjust the mechanical property of γ-InSe, and find that Y interstices could play an important role in improving the stiffness of γ-InSe. Our study provides theoretical insights for photovoltaic and other photoelectronic applications based on this interesting ferroelectric layered vdw material. [ABSTRACT FROM AUTHOR]

Ferroic compounds Fe2O(SeO3)2 (FSO) and Fe2(SeO3)3·3H2O (FSOH) prepared by the hydrothermal method are characterized and their optical properties are investigated by combining with first-principles calculations. The results show that (i) FSO is antiferromagnetic below ∼110 K and becomes ferromagnetic at elevated temperatures, while FSOH is antiferromagnetic at low temperatures probably due to a change in the spin state from Fe3+ (S = 5/2) to Fe2+ (S = 2); (ii) the optical bandgap is determined to be ∼2.83 eV for FSO and ∼2.15 eV for FSOH, consistent with the theoretical calculation; and (iii) the angle-resolved polarized Raman spectroscopy results of both crystals demonstrate the strong anisotropic light absorption and birefringence effects, and the unconventional symmetricity of some Raman modes is observed, which can be interpreted from the variation of Raman scattering elements. This work can provide not only an understanding of the structure and physical properties of iron selenites, but also a strategy for exploring the anomalous Raman behaviors in anisotropic crystals, facilitating the design and engineering of novel functional devices with low-symmetry ferroic materials. [ABSTRACT FROM AUTHOR]