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A GaInAsP/GaAs/GaAsP Al-free laser with asymmetric potential barriers is designed theoretically to prevent carrier leakage. The band alignment demonstrates that a high height of the potential barrier decreases the leakage current. The internal quantum efficiency increases by increasing the injection efficiency, which is attributed to the decreasing electron potential barrier heights. Moreover, the threshold current and operating voltage decrease by adopting a novel barrier so that the output power and power conversion efficiency (PCE) increase. When the injection current is 5 kA/cm

A GaInAsP/GaAs/GaAsP Al-free laser with asymmetric potential barriers is designed theoretically to prevent carrier leakage. The band alignment demonstrates that a high height of the potential barrier decreases the leakage current. The internal quantum efficiency increases by increasing the injection efficiency, which is attributed to the decreasing electron potential barrier heights. Moreover, the threshold current and operating voltage decrease by adopting a novel barrier so that the output power and power conversion efficiency (PCE) increase. When the injection current is 5 kA/cm2, the PCE is 77.82% and the output power is 13.21 W. The physical mechanism of potential barrier heights affecting carrier transport is investigated, which will provide a theoretical basis for optimizing laser diodes.

Ag/AgCl nanoparticles were immobilized onto the as-prepared CoFe2O4 fibers by a facile synthesis method. The amount of Ag/AgCl nanoparticles immobilized onto CoFe2O4 fibers could be tuned. The as-synthesized Ag/AgCl@CoFe2O4 composite fibers were characterized by XRD, FESEM and EM, and employed to degradate MO (methyl orange) dye in wastewater under visible light. The results show that AAC-4 fiber exhibits higher efficiency for the degradation of the MO dye under visible light illumination than other Ag/AgCl@CoFe2O4 composite fibers or pure Ag/AgCl sample, and the decolorizing efficiency of MO can research 98.2%. The immobilization of Ag/AgCl nanoparticles onto CoFe2O4 fiber promotes the enhancement of photocatalytic efficiency and stability.

Multi-layer optimization strategy plays a key role on solving multi-discipline optimization design (MDO) on the turbine. The main principle of MDO firstly extends to component autonomy from disciplinary autonomy. Based on component and discipline autonomy, this paper designs four kinds of MDO framework which are applied on the turbine design combining with present MDO strategies including BLISS2000, CO and ATC. Both the two-layer including double-subsystem and two-layer including triple-subsystem are built by BLISS2000 strategy as the two-layer framework for turbine design, while the threelayer including triple-subsystem strategy takes full advantage of BLISS2000 and CO stra tegies. Additionally, due to introduction of auxiliary variables and associated variables, the ATC optimization strategy requires huge extra optimization cost, so it is not suitable for triple-layer MDO strategy on turbine. Finally, the integrated MDO of disk and blade tests the former three kinds of MDO strategies. The preponderance of the MDO strategies including three subsystems is higher efficiency, while complex interactions between layers always lead to worse optimization accuracy and efficiency on three layers strategy comparing with two layers strategy.

In this paper, the influences of the growth time of low-temperature (LT) GaN nucleation layer on the crystal quality and optical properties of GaN film are investigated. It is found that the optimal LT nucleation layer growth time can effectively reduce the crystal defects and is favorable to forming the annihilation of dislocations. GaN films are grown on c-plane sapphire substrates by metal-organic chemical vapor deposition. Crystal quality and optical properties are characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution X-ray diffraction (HRXRD), and photoluminescence spectra, respectively. In the AFM images, the island density decreases as growth time increases, while the size of island becomes larger and the uniformity of island size deteriorates as growth time increases, leading to the phenomenon that the number of interfaces formed during the nucleation island coalescence, first decrease and then increase as detected by SEM, which also induces the screw dislocation density and edge dislocation density to first decrease and then increase as measured by HRXRD. This first-decrease-and-then-increase variation trend is consistent with the first-increase-and-then-decrease variation trend of the ratio of the band edge emission peak intensity to the yellow luminescence peak intensity tested by photoluminescence, which is confirmed by HRXRD. It is shown that GaN islands with different sizes and densities could lead to different mechanisms of dislocation evolution, thereby forming GaN epitaxial layers with different dislocation densities and optical properties. Through controlling the nucleation time, GaN films with the smallest dislocation density could be obtained.

To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.