We report on the growth and opto-electronic characterization of type-II InAs/GaSb superlattice (SL) mid-wavelength infrared pin photodetector grown on a GaAs substrate. AlSb interfacial misfit array was employed at the GaAs buffer/GaSb epilayer interface to reduce the dislocation density of the SL structure grown on the lattice mismatched GaAs substrate. Optical and electrical performance of this sample (SL-GaAs) were then compared with the reference sample of the same structure grown on a GaSb substrate (SL-GaSb). At 80 K, the dark current density and the detectivity values of the pin photodetectors were recorded as 5.40×10 −3 A cm −2 and 2.34×10 10 cm Hz 0.5 W −1 for the SL-GaAs and 9.50×10 −4 A cm −2 and 4.70×10 10 cm Hz 0.5 W −1 for the SL-GaSb, respectively.
Man–made fibers like carbon or glass are main components for fiber-reinforced polymer composites thanks to their high strength and stiffness values. However, man-made fibers are not eco-friendly and can hardly be recycled in the nature. Using a high amount of man-made fibers threatens our nature and poses a significant risk for the future of world. Natural fiber reinforced composite (NFRC) is considered as a good alternative for traditional composites. Therefore, NFRC has been examined to develop materials, which have comparable mechanical properties with the man-made fiber reinforced composites, for last decades. Although lots of studies were carried out on the mechanics of NFRC, a few of them focused on the structural design of reinforcement and their effects on composites performance. In this study, the number of weft densities of reinforcements were differentiated and their effects on the mechanical properties of composites were investigated. Fabrics were produced from flax yarns and composites were manufactured by vacuum assisted resin infusion molding method. The tensile, compression, shear and impact tests were carried out to characterize the manufactured composites. Results show that while increasing number of weft density of reinforcement improves the tensile and compressive strength of NFRC in the weft direction, the tensile strength and elastic modulus of composites in the warp direction were characterized by the crimp percentage values of warp yarns. Moreover, it was determined that the number of weft density in the reinforcement affect the contact force and energy absorption capacity of NFRC.
We report on the opto-electronic characterization of an InAs/GaSb superlattice (SL) midwave infrared p-i-n photodetector structure (pin-SL) in comparison with the same structure with no intentional doping (i-SL). Both structures were grown on an n-GaSb substrate using molecular beam epitaxy. The nominally undoped structure (i-SL) presented p-i-n like behavior and showed a photovoltaic mode photoresponse due to the residual doping and native defects in this material system. For ∼77 K operation, 0.76 and 0.11 A W -1 responsivity values were obtained at 4 μm from the pin-SL and i-SL structures, respectively. Activation energy analysis showed that the recombination current was dominant in both structures but different recombination centers were involved. The same i-SL structure was also grown on a semi-insulating (SI)-GaAs substrate to study the contribution of the substrate to the carrier density in the SL layers. Temperature dependent Hall effect measurements showed that the nominally undoped structure presented both n-type and p-type conductivities; however, the temperature at which the carrier type switched polarity was observed to be at higher values when the i-SL structure was grown on the SI-GaAs substrate. In addition, a higher carrier density was observed for i-SL on the GaSb substrate than on the GaAs substrate.
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