Interfacial Structure And Optical Properties Of Strained Inas/In_xGa_1-x Sb Superlattice

InAs/In_xGa_1-xSb strained layer superlattices have shown considerable promise as candidates for application in infrared detectors, particularly at wavelengths of 8¹4μm. The epitaxial growth of thin film heterostructures inevitably involves the formation of interfaces between layers of different materials. Both physical properties and device performance are crucially dependent on the interface structure and composition. The growth by Molecular beam epitaxy (MBE) enables the realization and control of atomically flat and chemically abrupt heterointerfaces. These are two major contributions to interfacial disorder: interfacial roughness due to the formation of steps and islands, and interfacial intermixing that comprises the changes in composition across the interface. Such interfacial disorder can ultimately impact the electrical and optical device characteristics by affecting transport and scattering mechanisms of carriers local deviations in the band offsets.The quality of interfaces depends on numerous growth parameters, substrate misorientation, properties of buffer layer, growth temperature and strain relaxation. This study was characterized quantify the structural properties of SL, and displayed optical properties by HRXRD, FTIR and PL.The interfacial structure of InAs/In_xGa1?xSb superlattices is investigated by high-resolution transmission electron microscopy (HRTEM). We have shown that high-resolution electron microscopy with quantitative image matching can enable the relative orientation of the closely separated atomic species in InAs and In_xGa1?xSb to be resolved. We have then used this capability to determine interfacial composition. The shift in the atomic positions associated with this modulation may lead to distortions of the interfacial structure of In_xGa1?xAs-like. The misfit dislocations in InSb-like interface are the primary mechanism for accommodating the lattice mismatch. The lattice structure of the InAs/In_xGa_1-xSb with GaAs/In_xGa_1-xAs-like interfaces has been studied. The atomic arrangement at the plane of the interface is analyzed based on the image characteristics. Possible bonding configurations are discussed. The results suggest that interface formation is first driven by charge balance. The shift of the interplanar separations associated with this modulation may lead to distortions of the interfacial structure of In_xGa_1-x As-like. The morphological characterization at GaAs-like interface is accompanied by interface misfit dislocations and compositional fluctuations near the interface.Atomic scale positional resolved lattice spacing measurement is used to study the In concentration of alloy layer in InAs/In_xGa_1-xSb superlattices. The unstrained lattice distance along three of [001], [110] and [111] directions were measured and calculated the average lattice constant. The experimental lattice constants of InAs layers are almost equal to the theoretical ones. We have calculated the average lattice constant of In_0.25Ga_0.75Sb alloy layers is in good agreement with previously reported Vegard's values. The results indicate that the In concentration of 0.18 has a same compared with the XRD values.The paper have shown how cross-sectional HRTEM can be used to characterize the lattice-mismatched bonding across the InAs/In_xGa_1-xSb interfaces with atomic scale precision, and described how such measurements advance our understanding of the connection between interfacial structure, interfacial composition, and the growth conditions used to form these complex hetero- structures. The interface type of InSb-like and In_xGa_1-xAs-like interface at InAs/In_xGa_1-xSb SLs was simulated based on kinetic theory of multi-method with the experimental micrographs. The atomic imaging across the interface on the impact of lattice spacing of high-resolution image was analyzed.This paper analyzes the microstructure characterization of InAs/In_xGa_1-xSb strained layer superlattices adapted for long wavelength and very long wavelength infrared photovoltaic thin film, and report on the physical nature and the relationship between interfacial structure and preparation technique. The connection between microstructure and optoeletronic performance has been analyzed based on"the band gap engineering"theoretical. Thus, the material system of the photovoltaic thin film is more attractive in achieving high performance infrared detectors for long wavelength and very long wavelength applications.