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GaAs solar cells can be grown with a fast growth rate without sacrificing the device performance. This paper investigates the effect of fast growth rate with metalorganic chemical vapor deposition (MOCVD) on GaAs single-junction solar cell crystal quality and device performance. The minority carrier lifetime of the samples grown with a fast growth rate (~56 µm/hr) was investigated. The growth parameters including growth temperature, V/III, and doping densities were varied to study the lifetime degradation mechanisms in the GaAs solar cell. In addition, Bi, as a surfactant, was used during the fast growth to improve the surface roughness compared to the standard growth methods with the growth rate of ~ 14 urn/hr. An epitaxial lift-off process was also designed to investigate the GaAs epitaxial quality on reused substrate. The goal of this work was to achieve a high quality GaAs solar cell with a fast growth on a reused GaAs substrate.

In this work, we investigate the effect of using bismuth as a surfactant during the growth of GaNAsSb solar cells lattice-matched to GaAs. First, we present a detailed analysis of the device characteristics grown without Bi. Low current collection, which was attributed to high acceptor background doping and hence, short depletion width, was found to be the main factor limiting the device performance. Bi surfactant was then introduced with relatively high fluxes during the growth of GaNxAsl-x-ySb y films. Preliminary investigation of material quality are presented. Upon tuning of the growth conditions, it is hoped that Bi will reduce the unintentional high p-type background doping and hence, improve the performance of these dilute nitride devices.

This work focuses on exploring the ways to integrate III-V nanostructures on silicon to enhance the current silicon cell's efficiency by effective absorption and possibly using quantum mechanical phenomena such as MEG (multiple exciton generation) and effective absorption of light above the band gap in the nanostructures' confined states. The gallium phosphide (GaP) is integrated with silicon wafers in the form of nanostructures. GaP is epitaxially grown on silicon, and the nanostructures are fabricated by silica nanospheres lithography (SNL) with metal assisted chemical etching (MACE). With optimized MACE condition, we are able to fabricate these nanopillars on GaP with controlled size and aspect ratios. Silica nanospheres are coated on the GaP is on Si by spin-coating, and their size is modified by a reactive ion etching (RIE) process. Palladium (Pd) is deposited on the sample by electron beam deposition for MACE process. In this MACE process, we control the MACE solution by changing the ration of HF and H2O2 concentrations. The GaP nanostructures created from MACE solutions with high HF and H2O2 concentrations is taller and possesses a more well-defined shape. Also, GaP nanostructures created from different metal of MACE such as Pd, Au and Ti/Au. MACE with Pd shows the better shape nanostructure than others.

The influence of Sc microalloying on compressive creep behaviors of Al-0.2Zr and Al-0.2Zr-0.1Sc alloy have been studied. The steady state creep rate of Al-0.2Zr-0.1Sc alloy ranged from 1.124 × 10−9 s−1 to 1.926 × 10−8 s−1 at 90–150 °C /70 MPa. By contrast, the steady state creep rate of Al-0.2Zr alloy ranged from 6.862 × 10−8 s−1 to 8.560 × 10−7 s−1, indicating that Sc addition significantly improve the compressive creep resistance of Al-0.2Zr alloy. According to the TEM micrographs, except for Al3(Zr,Sc) precipitates precipitated during aging, a large number of fine dispersed Al3Sc precipitates precipitated after creep for 70 h, which significantly hinder movements of dislocations and grain boundaries. As a result, the steady-state creep rate of Al-0.2Zr-0.1Sc alloy slightly decreases after 70 h at 150 °C /70 MPa. The critical creep stress value of Al-0.2Zr alloy is 47.2 MPa, and that of Al-0.2Zr-0.1Sc alloy is 68.4 MPa. The higher critical creep stress value indicates the more excellent compressive creep resistance.

Ho3+/Yb3+ co-doped tellurite-germanate glasses with lower phonon energy (779 cm−1) and higher thermal stability were prepared by conventional melt quenching. The mid-infrared fluorescence spectra of the prepared glasses were investigated by 980 nm laser pumping. The full width at half maximum (FWHM) and lifetime of the sample at 2.0 μm were 186 nm and 8.09 ms, respectively. Compared with the reported glasses for this type, these values were effectively improved. In particular, the FWHM and emission lifetime of the prepared glass at 4.1 μm reached 276 nm and 8.17 ms, respectively, which have not been reported yet. Meanwhile, compared to the recently reported tellurite glasses, the ΔT was increased by approximate 22.7%. Strong up-conversion visible emission peaks at 547, 662, and 756 nm and near-infrared emission at 1.20 μm were observed in Ho3+/Yb3+ co-doped glass. Meanwhile, photoluminescence measurements showed that the doping of the appropriate amount of Yb3+ ions significantly enhanced the emission intensity of the samples at 2.0 μm and 4.1 μm. Therefore, the Ho3+/Yb3+ co-doped tellurite-germanate glass is a promising candidate for mid-infrared fiber and laser materials applications.

A laser diode side pump all-solid-state pulse laser at 589 nm with high power and high conversion efficiency and small volume is demonstrated by intracavity sum frequency generation. By optimizing the cavity and adopting etalon techniques, a quasi continuous wave at 589 nm laser source, which has a maximum output power of 11.4 W, a repetition rate of 5 kHz, and a pulse width of 135 ns, is developed. The optical to optical conversion efficiency is up to 6.5% and the power stability is better than 2% in 8 hours.

BACKGROUND A procedure based on headspace solid phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC-MS) was developed for the study of the volatile profile characteristics of turbot during refrigerated storage at 4°C for 20 days in order to find possible markers of freshness or spoilage. RESULTS A total of 61 volatile compounds including aldehydes, ketones, esters, alcohols, alkenes, alkanes, aromatics, amines and others were identified in turbot muscle extracted by the optimised HS-SPME method. The volatile profile characteristics of turbot at different storage periods were specified by principal component analysis (PCA). The concentrations of hexanal, heptanal, (2E,4E)-heptadienal, acetophenone, 2-undecanone and 1-octen-3-ol decreased during storage, whereas benzene acetaldehyde, 6-methyl-5-hepten-2-one, 2-nonanone, acetic acid butyl ester, 3-methyl-1-butanol and trimethylamine increased. CONCLUSION SPME-GC-MS combined with PCA may be a useful method for monitoring the volatile profile characteristics of turbot during storage, which could be potentially used for freshness evaluation. © 2014 Society of Chemical Industry

We prepare three types of triply-doped-telluride glasses using the melting method. Under simultaneous dual-lasers (808 nm and 980 nm) excitation, seamless multiband near-infrared emission covering 1200–2100 nm is observed in the glasses for the first time, to the best of our knowledge. The seamless near-infrared emission has three emission bands, which peak at around 1337 nm, 1540 nm, and 1860 nm, and are assigned to the transitions of Nd3+:4F3/2→4I13/2, Er3+:4I13/2→4I15/2 and Tm3+:3F4→3H6, respectively. The triply-doped glasses are promising for applications in optical fiber communications, broadband fiber sources, and optoelectronics devices.

We report the velocity measurement of microscopic particles flowing at ultrahigh speed with optofluidic time-stretch microscopy at high throughput. This is a study of using optical time-stretch microcopy as a tool for particle velocimetry, where we developed a custom algorithm to process the images acquired from the optofluidic platform for the velocity calculation of individual particles. We experimentally determined the actual flow velocities for polystyrene microspheres with different sizes and traveling through the microchannel at a throughput of ∼10 000 particles/s. We also examined microfluidic channels with different aspect ratios (depth-to-width) for particle velocimetry. The result indicates a measurable flow velocity up to 2.51 m/s. Our method provides a promising tool for label-free and high-throughput particle velocimetry at high velocity magnitudes.We report the velocity measurement of microscopic particles flowing at ultrahigh speed with optofluidic time-stretch microscopy at high throughput. This is a study of using optical time-stretch microcopy as a tool for particle velocimetry, where we developed a custom algorithm to process the images acquired from the optofluidic platform for the velocity calculation of individual particles. We experimentally determined the actual flow velocities for polystyrene microspheres with different sizes and traveling through the microchannel at a throughput of ∼10 000 particles/s. We also examined microfluidic channels with different aspect ratios (depth-to-width) for particle velocimetry. The result indicates a measurable flow velocity up to 2.51 m/s. Our method provides a promising tool for label-free and high-throughput particle velocimetry at high velocity magnitudes.

A goal for concentrating photovoltaics is to realize efficiencies over 50%. Recent 4J bonded solar cells show a path to such high efficiency devices by separately growing the top and bottom solar cells. Present experimental devices use InP-based materials for the bottom junctions. III-Sb solar cells can be good candidates for bottom solar cells. Sb-containing III-V alloys have shown high electron mobility, wide band gap range including small band gaps, flexible band alignment, and small effective electron mass [1]. In addition, GaSb alloys can be grown with low defect densities on GaAs. This paper investigates GaSb-based solar cells. We show AlGaSb based solar cells grown directly on semi-insulator GaAs (001) substrates by Molecular Beam Epitaxy (MBE). Device and structural investigations have been performed to assess the electrical properties and material quality. Devices in the GaSb material system show Woc of 0.30, a very high value for a low band gap solar cell. To control the device properties, GaSb based solar cells grown on GaAs (100) substrates were compared to the devices grown on GaSb substrates.

A major hindrance to the development of devices integrating III-V materials on silicon is the preservation of its electronic quality. In this contribution, we report on the severe decrease in silicon bulk minority-carrier lifetime after heteroepitaxial growth of gallium phosphide, in our molecular beam epitaxy (MBE) system. The drop in lifetime occurs after annealing silicon above 500°C; we assign the increased recombination rate to extrinsic defect originating from highly mobile impurities diffusing from the MBE chamber. We show that the contaminant can be gettered by phosphorous diffusion. We investigate two approaches to protect the Si bulk lifetime by containing the contaminant to a part of the silicon that can be removed by etching. This provides a path to successful III-V growth on silicon.

III-V/silicon solar cells which have an active silicon bottom solar cell are promising for multi-junction solar cell applications. In such solar cell structures, a high minority carrier lifetime in the bulk silicon substrate is necessary. Annealing silicon wafers at high temperature (> 500oC) in the molecular beam epitaxy (MBE) high-vacuum chamber revealed significant lifetime degradation. In this work, we developed a practical method to maintain high Si bulk lifetime. SiN x layer deposited on Si back side helps maintain millisecond level minority carrier lifetime. By this procedure high minority carrier lifetime in the Si substrate is preserved while high quality thin GaP layer is achieved. We demonstrate GaP as a hetero-emitter layer with high Si bulk lifetime in GaP/Si structure solar cell with 524mV open circuit voltage.

We design an in-plan hetero-photonic crystal (IP-HPC) structure which can dynamically control the quality (Q) factor of the nanocavity by using Kerr effect. In both theoretical derivation and numerical simulation, the Q factor could be dynamically turned with a larger scale than reported before. We study the effect of distance between the cavity and the hetero-photonic crystal on the Q factor. With optimal parameters, the Q factor of the nanocavity can be changed from ∼130,000 to ∼880,000 in the IP-HPC system.

Output nonlocality and nonclassicality for the two modes are investigated in an entanglement laser system. Within the framework of a quantum theory of multiwave mixing, nonlocality and nonclassicality are discussed according to the violations of Bell inequality and Cauchy-Schwarz inequality. It is found that both nonlocality and nonclassicality can be fulfilled in the outside cavity fields under certain conditions. It is also shown that there are some nonclassical states that do not show nonlocality.

Highly doped GaN p–n tunnel junction (TJ) contacts to InGaN solar cells are demonstrated, in which the TJs were grown by molecular beam epitaxy on top of active solar cell regions grown by metalorganic chemical vapor deposition. The effects of Si and Mg doping concentrations on solar cell characteristics are studied and used to improve turn-on voltage and series resistance. The highest doped cell with a TJ has an open-circuit voltage of 2.2 V, similar to that of the control cell fabricated using indium tin oxide (ITO), and a far less short-circuit current density loss from unwanted photogeneration in the TJ contact than in the ITO contact.

La2O3 and ZrO2 co-doped silicate glasses were fabricated using melt-quenching method. The network structure, Vickers hardness and elastic modulus of the glasses were measured to investigate their mechanical properties. Our results indicated that the prepared samples exhibited high strength network structures with excellent mechanical performance. The Vickers hardness exceeded 858[Formula: see text]HV, and the elastic modulus reaches 100[Formula: see text]GPa. They increased approximate 37% and 18.6%, respectively, more than the most hardness and modulus reported for this type of glasses, while their transmittance in visible spectrum range was over 90%.

Single-junction GaAs-based solar cell structures are grown by metalorganic chemical vapor deposition system at the growth rates of 14 µm/hr and 56 µm/hr. The X-ray diffraction study reveals that the crystal quality of the structures with varying the growth rates is comparable. From the external quantum efficiency spectra, it is observed that different behaviors exist in the short wavelengths ( 500 nm) as the growth rate increases. The short-circuit current densities of the standard and fast grown cells are comparable. However, the open-circuit voltage of the fast grown cell is lower by above 40 mV as a result of the reduced minority carrier lifetime in the base layer, which is estimated by PC1D simulation.

The structural characteristics and device performance of strain-compensated InAs/GaAsSb quantum dot solar cells (QDSCs) with different GaP coverages have been studied. The in-plane (out-of-plane) compressive strain of the QD stacks is reduced from −1.24 (+1.06) to −0.39 (+0.33)% by increasing the GaP coverage from 0 to 4 ML. This strain compensation decreases strain-induced dislocation density and hence enhances the overall crystal quality of the QDSCs. The external quantum efficiency spectra reveal that the increase in the GaP coverage increases the photocurrent from wavelengths shorter than GaAs bandedge of 880 nm, while it decreases the photocurrent from near infrared wavelengths beyond the bandedge. The conversion efficiency of the QDSCs is significantly improved from 7.22 to 9.67% as the GaP coverage is increased from 0 to 4 ML.

By coating with a carbon film and graphene sheet (GS) on position-sensitive detectors based on the metal–oxide–semiconductor structure, sensitivity, linearity, and saturation power are significantly improved. We attribute this enhancement of absorptivity to lasers. The improvement effect of carbon film is more obvious than that of GS coating because of GS’s high conductivity.

We have studied the material and photovoltaic characteristics of InAs/GaAsSb sub-monolayer quantum dot solar cells (QDSCs) with different Sb contents of 0%, 5%, 15%, and 20%. All QDSCs exhibit an extended external quantum efficiency (EQE) response in the wavelength range of 960–1000 nm that corresponds to sub-bandgap photon absorption. As Sb content increases from 5% to 20%, the cutoff wavelength in the EQE extends towards longer wavelength whilst the EQE in the wavelength region of 300–880 nm is lowered due to increased defect density. Compared to the QDSC (Sb 0%), an Sb incorporation of 5% enhances the short-circuit current density from 20.65 to 22.15 mA/cm2 induced by Sb surfactant effect. Since the open-circuit voltage and fill factor of the QDSC (Sb 5%) are comparable to those of the QDSC (Sb 0%), an enhancement in solar cell efficiency (10.5%) of the QDSC (Sb 5%) is observed. Further increasing Sb content to 15% and 20% results in the degradation of solar cell performance due to increased nonradiati...

The continuous-variable (CV) entanglement of the output fields is investigated in a four-level correlated emission laser system. The atomic coherence is introduced using two external classical driving fields. Based on the input–output theory, it is shown that the output entanglement and the entangled photons of the system can be achievable under certain conditions. Moreover, it is found that the two-mode entanglement has a close relation with the intensities of two external driving fields.