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Epitaxial layers of the solid solution of molecular substitution (Si2)1-x(GaP)x (0 ≤ x ≤ 1) on Si (111) and GaP (111) substrates are grown by liquid-phase epitaxy from an Sn solution-melt. Such graded-gap solid solutions allow the integration of well-established silicon technology with the advantages of III-V semiconductor compounds. The structural features, the distribution of the atoms of the components over the thickness of the epitaxial layer, the photoluminescence spectrum of the (Si2)1-x(GaP)x (0 ≤ x ≤ 1) solid solution, and the electroluminescence of the structure n-GaP-n+-(Si2)x (GaP)1-x (0 ≤ x ≤ 0.01) have been investigated. It is shown that the layers of the solid solution have a perfect single-crystal structure with the crystallographic orientation (111), with the size of subcrystallites ∼ 39 ± 1 nm. The epitaxial layer (Si2)1-x(GaP)x (0 ≤ x ≤ 1) is a graded-gap layer with a smoothly and monotonically varying composition from silicon to 100% GaP. The energy levels of atoms of Si2 molecules which are located 1.47 eV below the bottom of the conduction band of gallium phosphide are revealed. Red emission of n-GaP-n+-(Si2)x(GaP)1-x (0 ≤ x ≤ 0.01) structure which is caused by electron transitions with participation of energy levels of Si2 atoms is detected.

The polytypism of solids has been established as one of the most effective approaches to alter their physical properties. In this first-principles-based study, we practiced the polytypism of galliu...

Photoelectrosynthetic materials provide a bioinspired approach for using the power of the sun to produce fuels and other value-added chemical products. However, there remains an incomplete understanding of the operating principles governing their performance and thereby effective methods for their assembly. Herein we report the application of metalloporphyrins, several of which are known to catalyze the hydrogen evolution reaction, in forming surface coatings to assemble hybrid photoelectrosynthetic materials featuring an underlying gallium phosphide (GaP) semiconductor as a light capture and conversion component. The metalloporphyrin reagents used in this work contain a 4-vinylphenyl surface-attachment group at the β-position of the porphyrin ring and a first-row transition metal ion (Fe, Co, Ni, Cu, or Zn) coordinated at the core of the macrocycle. In addition to describing the synthesis, optical, and electrochemical properties of the homogeneous porphyrin complexes, we also report on the photoelectrochemistry of the heterogeneous metalloporphyrin-modified GaP semiconductor electrodes. These hybrid, heterogeneous-homogeneous electrodes are prepared via UV-induced grafting of the homogeneous metalloporphyrin reagents onto the heterogeneous gallium phosphide surfaces. Three-electrode voltammetry measurements performed under controlled lighting conditions enable determination of the open-circuit photovoltages, fill factors, and overall current–voltage responses associated with these composite materials, setting the stage for better understanding charge-transfer and carrier-recombination kinetics at semiconductor|catalyst|liquid interfaces.

Schottky barriers (SBs) based on gallium phosphide (GaP) attract researchers’ attention as promising structures for the development of various types of radiation-resistant electronic and photovoltaic devices, including high-temperature devices, high-frequency power electronics, ultraviolet (UV) photoelectronics and solar energy. This work studies photoelectric properties of surface-barrier (SB) structures of Au-palladium-n-GaP in the visible spectrum range under the action of both natural and polarized radiation, in order to obtain new data on the barrier height, band structure of GaP and the interface metal semiconductor.In particular, nanostructured Au-palladium-n-GaP structures were examined.The initial material for the structures production - n-GaP plates [n = (0.1-5) · 1017 cm-3, 300 K] with a thickness of 350-400 µm, oriented in the crystallographic plane (100), grown with the Czochralski method. Studying photosensitivity of nanostructured structures of the Au-Pd-n-GaP type in the visible spectrum range gives important information about the parameters of the potential barrier, the band structure of the semiconductor. Thus, the intermediate Pd (palladium) nanolayer between GaP and Au with a thickness of 20-30 A creates specific properties in the Au-Pd-n-GaP nanostructure that are of great scientific and practical importance.

In this paper, the optical and luminescent properties of gallium phosphide (GaP) and spectral characteristics of GaP p-n, m-s structures for studying the energy-band structure of GaP were considered. Based on literature data, the absorption coefficient dependence was constructed near and above the fundamental absorption edge of the photon energy hν=2-6 eV in GaP (300 K) to discuss the obtained experimental results. The results of the photosensitivity spectra study of Au-n-GaP, Au-p-GaP Schottky barriers are presented, which were produced by the chemical deposition of Au nanoscale (~15 nm) on the GaP surface. By comparing the absorption spectrum of GaP with the photocurrent spectra of Au-n-GaP and Au-p-GaP structures in the visible and ultraviolet (UV) region of the spectrum, it has been established that usually the photocurrent (

Resonant metasurfaces are an attractive platform for enhancing the non-linear optical processes, such as second harmonic generation (SHG), since they can generate very large local electromagnetic fields while relaxing the phase-matching requirements. Here, we take this platform a step closer to the practical applications by demonstrating visible range, continuous wave (CW) SHG. We do so by combining the attractive material properties of gallium phosphide with engineered, high quality-factor photonic modes enabled by bound states in the continuum. For the optimum case, we obtain efficiencies around 5e-5 % W$^{-1}$ when the system is pumped at 1200 nm wavelength with CW intensities of 1 kW/cm$^2$. Moreover, we measure external efficiencies as high as 0.1 % W$^{-1}$ with pump intensities of only 10 MW/cm$^2$ for pulsed irradiation. This efficiency is higher than the values previously reported for dielectric metasurfaces, but achieved here with pump intensities that are two orders of magnitude lower.

The paper shows the results of the development of a photodiode technology based on gallium phosphide structure n+-n-GaP-Au with high sensitivity. It provides the ion etching of the surface of the gallium phosphide before an application of a leading electrode of gold. The barrier layer of a 20 nm thick gold is applied to the substrate in the magnetic field of GaP. When forming the contact with the reverse side of the indium substrate at 600°C, there occurs the annealing of the gold barrier layer. At the maximum of the spectral characteristics obtained by the photodiode, it has a sensitivity of 0.13 A/W, and at a wavelength of 254 nm – about 0.06 A/W. The dynamic range of the photodiode is not less than 107.

The photovoltaic characteristics of a mechanically and monolithic stacked tandem solar cell of the heterojunction InGaP/GaAs and Ge sub cells, were numerically simulated under 1-sun air mass 1.5 global spectrum (AM1.5G) at ambient temperature (300 K) using the two-dimensional device simulator Silvaco–Atlas. Our tandem structure consists of a thin upper cell with heterojunction of indium and gallium phosphide on gallium arsenide (In0.49Ga0.51P/GaAs), on a relatively thick germanium (Ge) substrate which acts as a lower cell in order to obtain good performances of such a structure. We studied both cells, stacked mechanically (four terminal:4T) and monolithic (two terminal:2T) using Silvaco ATLAS Virtual Wafer FabricationTool. First, we have simulated the single InGaP/GaAs and Ge solar cells with fixed thicknesses at 1.4 µm and 210 µm respectively. They presented a conversion efficiencies (ƞ) of 30.32% and 10.96% respectively. The efficiency of mechanically stacked tandem solar is 30.96% and short current density of 26.16 mA/cm2 which is limited by the lower short current density of both sub-cells. Using the method of current matching, by varying the base thicknesses of the InGaP/GaAs top and Ge bottom sub-cells, the numerical simulation results presented a matched maximum current Jsc value of 29.12 mA/cm2 obtained at base thicknesses of 0.605 and 209.9 μm for the InGaP/GaAs top and Ge bottom sub-cells respectively, leading to a high power conversion efficiency (ƞ) of the mechanically stacked sub cells of 34.77%, the open-circuit voltage and the fill factor are 1.329 V and 88.96%, respectively. Next, the sub-cells were interconnected with tunnel junctions (TJs), p-GaAs/n-GaAs to allow carrier transport, the results of the monolithic stacked sub-cells are converged with results of the mechanically stacked sub-cells, and are represented in the following results of the tandem cell: power conversion efficiency (ƞ) of 32.96%, the open-circuit voltage of 1.343 V, the short current of 29.19 mA/cm2 and the fill factor of 84.05%.

In this work, the effects of x-value on electrical and optical properties was studied for the two dimensional (2D)GaAs1-xPxstructure by applying the density functional theory.We found that the gallium arsenide(GaAs) and gallium phosphide(GaP) monolayers are bound to each other, while the charge transfer between these two materialsleads to tuning the band gap value between 1.5 eV for GaAs to 2.24 eV for GaP. The density of state, band structure, and optical properties are investigated in this paper.

Gallium phosphide (GaP) solar cell structures with improved quantum efficiencies were realized using a modified liquid phase epitaxy (LPE) technique and diodes formed using semi-transparent Schottky contacts. The improvement is due to the addition of a small amount of aluminum to the gallium and phosphorus containing LPE melt. The Al reduces the background concentration of oxygen in the melt, which is known to produce deep trap states in GaP. Additionally, it was found that by depositing an aluminum (Al)-rich AlGaP layer on top of the active GaP and then selectively etching it away, the surface morphology of the active layer was significantly improved. Thus, the modified LPE technique eliminates the major problem of meniscus lines associated with the standard LPE method.

Chloride-hydride epitaxy is the main vapor-phase technique for forming layers of functional homostructures and heterostructures for microelectronics and optoelectronics. At present, nanoheterostructures are obtained by MOS-hydride and molecular epitaxy; the molecular-layering technique is currently being perfected. The occurrence of new materials requires long-term development of the optimal technological conditions for their fabrication and the mathematical, physical, and other principles for modeling these processes. The chloride-hydride method continues to be perfected for forming relatively thick layers of functional heterostructures. The work outlines the fundamentals of physicochemical modeling by the example of chloride-hydride epitaxy. A physicochemical model of the variation in the technological modes of the vapor-phase epitaxy of different compounds under the corresponding conditions, which facilitate the formation of compounds with the same degree of disorder, is discussed. Equations for predicting the conditions for the epitaxy of other materials of the same group by the well-developed technology of a material have been derived. The obtained regularities can be used to optimize the chloride-hydride epitaxy of gallium phosphide and solid solutions based on it. The calculated conditions for gallium-nitride epitaxy are shown to be in good agreement with the conditions of real technological developments made by other authors.

Gallium phosphide (GaP) is an indirect bandgap semiconductor used widely in solid-state lighting. Despite numerous intriguing optical properties---including large $��^{(2)}$ and $��^{(3)}$ coefficients, a high refractive index ($>3$), and transparency from visible to long-infrared wavelengths ($0.55-11\,��$m)---its application as an integrated photonics material has been little studied. Here we introduce GaP-on-insulator as a platform for nonlinear photonics, exploiting a direct wafer bonding approach to realize integrated waveguides with 1.2 dB/cm loss in the telecommunications C-band (on par with Si-on-insulator). High quality $(Q> 10^5)$, grating-coupled ring resonators are fabricated and studied. Employing a modulation transfer approach, we obtain a direct experimental estimate of the nonlinear index of GaP at telecommunication wavelengths: $n_2=1.2(5)\times 10^{-17}\,\text{m}^2/\text{W}$. We also observe Kerr frequency comb generation in resonators with engineered dispersion. Parametric threshold powers as low as 3 mW are realized, followed by broadband ($>100$ nm) frequency combs with sub-THz spacing, frequency-doubled combs and, in a separate device, efficient Raman lasing. These results signal the emergence of GaP-on-insulator as a novel platform for integrated nonlinear photonics., 13 pages, 10 figures, 1 table; typos corrected, added/fixed references, modified title

Indium gallium phosphide (InGaP) solar cell with a superior high-radiation resistance is expected to be a powerful candidate for a dosimeter under a high-radiation dose rate environment. In...

Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures. Here, we couple monolayer WSe2 to high-refractive-index gallium phosphide dielectric nano-antennas providing both optical enhancement and monolayer deformation. For single photon emitters formed on such nano-antennas, we find very low (femto-Joule) saturation pulse energies and up to 104 times brighter photoluminescence than in WSe2 placed on low-refractive-index SiO2 pillars. We show that the key to these observations is the increase on average by a factor of 5 of the quantum efficiency of the emitters coupled to the nano-antennas. This further allows us to gain new insights into their photoluminescence dynamics, revealing the roles of the dark exciton reservoir and Auger processes. We also find that the coherence time of such emitters is limited by intrinsic dephasing processes. Our work establishes dielectric nano-antennas as a platform for high-efficiency quantum light generation in monolayer semiconductors., Single photon emitters (SPEs) in 2D semiconductors can be deterministically positioned using localized strain induced by underlying nanostructures. Here, the authors show SPE coupling in WSe2 to GaP dielectric nanoantennas, substantially increasing quantum efficiency and photoluminescence brightness.

Tailoring optical properties in photocatalysts by nanostructuring them can help increase solar light harvesting efficiencies in a wide range of materials. Whereas plasmon resonances are widely employed in metallic catalysts for this purpose, latest advances of nonradiative, dielectric nanophotonics also enable light confinement and enhanced visible light absorption in semiconductors. Here, a design procedure for large-scale nanofabrication of semiconductor photoelectrodes using imprint lithography is developed. Anapole excitations and metasurface lattice resonances are combined to enhance the absorption of the model material, amorphous gallium phosphide (a-GaP), over the visible spectrum. It is shown that cost-effective, high sample throughput is achieved while retaining the precise signature of the engineered photonic states. Photoelectrochemical measurements under hydrogen evolution reaction conditions and sunlight illumination reveal the contributions of the respective resonances and demonstrate an overall photocurrent enhancement of 5.7, compared to a planar film. These results are supported by optical and numerical analysis of single nanodisks and of the upscaled metasurface.https://onlinelibrary.wiley.com/doi/10.1002/aenm.202102877

Optical resonances arising from quasi-bound states in the continuum (QBICs) have been recently identified in nanostructured dielectrics, showing ultrahigh quality factors accompanied by very large electromagnetic field enhancements. In this work, we design a periodic array of gallium phosphide (GaP) elliptical cylinders supporting, concurrently, three spectrally separated QBIC resonances with in-plane magnetic dipole, out-of-plane magnetic dipole, and electric quadrupole characters. We numerically explore this system for second-harmonic generation and degenerate four-wave mixing, demonstrating giant per unit cell conversion efficiencies of up to ∼ 2 W−1 and ∼ 60 W−2, respectively, when considering realistic introduced asymmetries in the metasurface, compatible with current fabrication limitations. We find that this configuration outperforms by up to more than four orders of magnitude the response of low-Q Mie or anapole resonances in individual GaP nanoantennas with engineered nonlinear mode-matching conditions. Benefiting from the straight-oriented electric field of one of the examined high-Q resonances, we further propose a novel nanocavity design for enhanced spectroscopies by slotting the meta-atoms of the periodic array. We discover that the optical cavity sustains high-intensity fields homogeneously distributed inside the slot, delivering its best performance when the elliptical cylinders are cut from end to end forming a gap, which represents a convenient model for experimental investigations. When placing an electric point dipole inside the added aperture, we find that the metasurface offers ultrahigh radiative enhancements, exceeding the previously reported slotted dielectric nanodisk at the anapole excitation by more than two orders of magnitude.

Most researchers proposed the surface plasmon resonance (SPR) sensor in the visible light range only. This paper presents performance enhancement of SPR sensor based on molybdenum disulphide (MoS 2 )-Dielectric matertals-MoS 2 -structure in Near Infrared (NIR) region for urea detection. The proposed structure consists of six layers, and the gold (Au) is used as a plasmonic material to improve its performance. The double MoS 2 layers are coated on both surfaces of dielectric materials such as germanium oxide (GeO 2 ) and gallium phosphide (GaP), which are used as protective layers and bio-recognition elements to enhance SPR performance. In this study, we have considered two different urea concentrations of 2.5 and 5gm/dl as a sensing medium, having RIs of 1.339 and 1.342, whereas the normal urea RI is 1.335. The performance is analyzed numerically at 785nm wavelength applying the transfer matrix method. Initially, the performance investigates the optimized thickness of Au using the iteration method. Further, the outcome results are shown in terms of sensitivity and quality factor (QF), and the maximum achieved performances are S of 280°/RIU and QF of 41.36RIU−1 at a change in sensing RI of 0.007. Finally, the proposed structure performance is compared to existed SPR structures done by other researchers.

Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask. Above that, we present the strategy for controlling both GaP NW length and diameter independently in single- or two-staged self-catalyzed growth. The proposed approach can be extended to other III-V NWs.

High harmonic generation (HHG) opens a window on the fundamental science of strong-field light-mater interaction and serves as a key building block for attosecond optics and metrology. Resonantly enhanced HHG from hot spots in nanostructures is an attractive route to overcoming the well-known limitations of gases and bulk solids. Here, we demonstrate a nanoscale platform for highly efficient HHG driven by intense mid-infrared laser pulses: an ultra-thin resonant gallium phosphide (GaP) metasurface. The wide bandgap and the lack of inversion symmetry of the GaP crystal enable the generation of even and odd harmonics covering a wide range of photon energies between 1.3 and 3 eV with minimal reabsorption. The resonantly enhanced conversion efficiency facilitates single-shot measurements that avoid material damage and pave the way to study the controllable transition between perturbative and non-perturbative regimes of light-matter interactions at the nanoscale., Strong nonlinearities, like high harmonic generation in optical systems, can lead to interesting applications in photonics. Here the authors fabricate a thin resonant gallium phosphide metasurface capable of avoiding the laser-induced damage and demonstrate efficient even and odd high harmonic generation from it when driven by mid-infrared laser pulses.

Between two-dimensional (2D) semiconductors, the family of transition metal dichalcogenides (TMDs) exhibits promising optical properties, such as tightly bound excitons and single photon emitting centers, with favourable integration in current nano-photonic architectures. High refractive-index dielectrics have recently gained attention as they exhibit optical Mie resonances, offering a novel platform to engineer light-matter interaction down to sub-wavelength dimensions. In our work, we integrated single and double layer TMDs WSe 2 with Mie-resonant gallium phosphide (GaP) dimer nano-antennas and demonstrate the enhancement of the light-matter interaction of 2D excitons and relative single photon emitters.

Semiconductor nanowires (NW) have received much attention for their unique properties providing exceptional flexibility in device engineering. In particular, gallium phosphide NWs demonstrate effective wave-guiding properties and broadband nonlinear frequency conversion, and find applications in green to amber optical range optoelectronics and photocatalytic devices. They also exhibit one of the broadest transparency range, high values of the nonlinear refractive index and good thermal conductivity that make them perspective for nanophotonics.

Gallium Phosphide (GaP) is a material with outstanding optical properties and a promising candidate for nanophotonic applications. Among comparable materials, it is one with the highest linear refractive indices and due to its wide and indirect bandgap, it has a lossless transparency for wavelengths longer than 450 nm. The bulk crystal was already shown to have a strong ultrafast response [1] and nanostructuring of a GaP wafer led to a record conversion efficiency in second-harmonic generation (SHG) [2] . Nevertheless, such structures are based on a high refractive index substrate and therefore no optical contrast in that direction. This prevents strong optical resonances and therefore naturally limits nonlinear efficiencies.

The paper presents a numerical simulation of novel Indium Nitride and Gallium Phosphide based GaN-BTG (Buffer Trenched Gate) MOSFET. The electrical characteristics such as Transfer characteristics, Transconductance, Electron mobility of InN-GaN-BTG-MOSFET and GaP-GaN-BTG-MOSFET are exhaustively analyzed using the Atlas TCAD tool. A comprehensive study is presented comparing the InN-GaN-BTG-MOSFET with GaN-BTG and GaP-GaN-BTG MOSFETs in terms of their performance characteristics. An improvement of 60.48% in SS and an increment of 47.16% in the electric field is observed which is because of the appliance of GaP and InN in the GaN-BTG structure. InN-GaN-BTG-MOSFET proves to be a promising structure to obtain enhanced performance for sub-20nm transistors and may be used for further scaling up the device.

This article presents results of research work aimed at manufacturing photoconductive semiconductor switches (PCSSs) based on semi-insulating (SI) gallium phosphide (GaP) and gallium nitride (GaN). Currently, the work is in progress to determine the optimal values of PCSS parameters. In this article, the parameters of the selected semiconductor materials used for making PCSSs, the device operation principle, and possible areas of use are presented. The paper demonstrates the construction of test PCSSs based on SI GaP and SI GaN and results of blocking characteristics measurements without the illumination, as well as with illumination with a small photon flux. Further research directions are presented also.

Raman light scattering on phonons and polaritons is measured in a gallium phosphide sample. An unfocused beam of a 532-nm single-mode laser was used for excitation. A scattered radiation was collected using a mobile mirror of a small diameter, which allowed us to measure spectra of scattered light in a 0.6°–8° range of scattering angles with a total angular spread of 0.4°. For different crystallographic directions, intensities of polarized components of the Raman light scattering on longitudinal, transverse phonons and polaritons were measured in the region of a strong dispersion of the polaritonic branch for three fixed axial scattering angles. Components of scattering on longitudinal optical phonons and polaritons have a strong dependence on a crystallographic direction, as predicted by theory, and the component of scattering on transverse optical phonons did not depend on a crystallographic direction. It was found that the intensity of scattering on transverse optical phonons correlates with a width of a spectral line of scattering on polariton. A mechanism explaining this correlation is proposed.

Thin films of gallium-phosphorus-titanium (Ga-P-Ti) alloys were prepared on glass substrates at 573 K by an asymmetric bipolar pulsed direct current sputtering technique using an argon atmosphere and targets made from gallium phosphide (GaP) powder and metallic titanium (Ti), at the surface ratios of 8:1, 5:1, 2:1 and 1:1 GaP to Ti (GaP:Ti) on the sputtered area. Examination by X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscope indicated that the as-deposited films from the sputtering targets having GaP:Ti ratios of 8:1, 5:1, and 2:1 were polycrystalline with the cubic zinc-blende crystal structure having GaP as the host material, i.e., Ti-doped GaP. Elemental compositions of the film obtained from the target at a GaP:Ti ratio of 5:1 closely resembled the theoretically predicted intermediate band compound Ga4P3Ti. It was projected that the Ga4P3Ti compound could be fabricated by co-sputtering of GaP and Ti from a single target having the surface area ratio GaP:Ti of 3.5:1. Optical transmission and reflection spectra, temperature dependence of electrical resistivity, and light response of the electrical resistivity showed semiconductor-like behavior for the films obtained from the targets with the GaP:Ti of 8:1 and 5:1, and were metal-like for those deposited from the other targets. Optical band gaps determined from the transmission spectrum of the semiconducting films by Tauc's expression for indirect transition were 1.2–1.5 eV. The results of the study could provide an alternative route for fabricating the intermediate band material based on the Ga-P-Ti system.

Light-matter interactions with two-dimensional materials gained significant attention in recent years, leading to the reporting of weak and strong coupling regimes and effective nanolaser operation with various structures. Particularly, future applications involving monolayer materials in waveguide-coupled on-chip-integrated circuitry and valleytronic nanophotonics require controlling, directing, and optimizing photoluminescence. In this context, photoluminescence enhancement from monolayer transition-metal dichalcogenides on patterned semiconducting substrates becomes attractive. It is demonstrated in our work using focused-ion-beam-etched GaP and monolayer WS2 suspended on hexagonal boron nitride buffer sheets. We present an optical microcavity approach capable of efficient in-plane and out-of-plane confinement of light, which results in a WS2 photoluminescence enhancement by a factor of 10 compared to that of the unstructured substrate at room temperature. The key concept is the combination of interference effects in both the horizontal direction using a bull's-eye-shaped circular Bragg grating and in the vertical direction by means of a multiple-reflection model with optimized etch depth of circular air-GaP structures for maximum constructive interference effects of the applied pump and expected emission light.

A design approach for flat metasurface devices is proposed and applied to design the broadband reflectors in the visible regime. Firstly, the geometry parameters of metasurfaces which comprise a monolayer amorphous titanium dioxide nanorod array in the air are optimized to achieve a broadband perfect reflector whose bandwidth is about 90 nm. Further, for practical application, the geometry parameters of a metasurface which is composed with a monolayer gallium phosphide nanoparticle (rod or cuboid) array on a glass substrate are optimized to achieve excellent reflection performance. Such all-dielectric metasurface near perfect reflectors can be used to protect surfaces against high power irradiation and create low loss mirrors in laser cavities. The design approach presented in this work is based on utilizing genetic optimization algorithm in order to determine the scatterers dimensions and lattice period within a unit-cell of the metasurface. The approach exhibits great superiority on the design of perfect reflectors and can be extended to design more complex flat components such as metalenses, holograms and deflectors. This approach is expected to provide a guideline for designing multifunctional photonic metamaterial devices.

One-dimensional semiconductor nanowires often contain polytypic structures, owing to the co-existence of different crystal phases. Therefore, understanding the properties of polytypic structures is of paramount importance for many promising applications in high-performance nanodevices. Herein, we synthesized nanowires of typical III–V semiconductors, namely, gallium phosphide and gallium arsenide by using the chemical vapor transport method. The growth directions ([111] and [211]) could be switched by changing the experimental conditions, such as H2 gas flow; thus, various polytypic structures were produced simultaneously in a controlled manner. The nanobeam electron diffraction technique was employed to obtain strain mapping of the nanowires by visualizing the polytypic structures along the [111] direction. Micro-Raman spectra for individual nanowires were collected, confirming the presence of wurtzite phase in the polytypic nanowires. Further, we fabricated the photodetectors using the single nanowires, and the polytypic structures are shown to decrease the photosensitivity. Our systematic analysis provides important insight into the polytypic structures of nanowires.

A novel design of Hexa Sectored Photonic Crystal Fiber (HS-PCF) with high nonlinearity and high birefringence has been revealed in this paper where core is slotted and filled with Gallium Phosphide (GaP). Finite Element Method has been used for numerical investigation of the proposed PCF along with finer mesh. Different optical parameters like nonlinearity, effective area, power fraction, birefringence, confinement loss and Numerical Aperture (NA) have been explored by proper tuning of Geometrical variables. The investigation shows that, proposed PCF exhibits high nonlinearity of 9.47 × 104 W−1Km−1 at the operating wavelength of 1.4 µm along with high birefringence of 0.259, Numerical aperture of 0.8774 and very low confinement loss of 5.78 × 10−9 dB/m at the optical wavelength of 2.0 µm. Therefore, it is expected that this proposed PCF could be a strong candidate in biomedical imaging, super continuum generation and sensing applications considering polarized light. Keywords: Photonic crystal fiber, Birefringence, Low confinement loss, Nonlinearity, GaP strips, Slotted core

This contribution brings novel concept of Ag islands formation in 2D periodic arrangement with square symmetry on special 3D surfaces – gallium phosphide (GaP) nanocones, for surface-enhanced Raman spectroscopy application. 2D periodic structure in square symmetry with period of app. 470 nm is patterned in photoresist layer by interference lithography using double exposure of a two-beam interference optical field. Two different techniques for photoresist deposition on 3D surface are compared: spin-coating and photoresist deposition from water level. After Ag sputtering and lift-off, GaP nanocones are decorated with Ag islands in 2D periodical arrangement. Detectable enhancement in Raman signal for Rhodamine 6G adsorbed on prepared samples is demonstrated.

In order to overcome the limitations of silicon-based electronics, the integration of optically active III-V compounds is a promising approach. Nonetheless, their integration is far from trivial and control as well as understanding of corresponding growth kinetics, and in particular the occurrence and termination of antiphase defects, is of great relevance. In this work, we focus on the three-dimensional reconstruction of such boundaries in gallium phosphide from single scanning transmission electron microscopy images. In the high angle annular dark-field imaging mode, the appearance of these antiphase boundaries is strongly determined by the chemical composition of each atomic column and reflects the ratio of transmitted anti- to mainphase. Therefore it is possible to translate measured intensities to the depth location of these boundaries by utilizing simulation data. The necessary spatial resolution for these column-by-column mappings is achieved via electron optical aberration correction within the microscope. Hence, the complete 3D orientation of these defects can be measured at atomic resolution and correlated to growth parameters. Finally, we present a method to reconstruct large areas from well sampled images and retrieve information about complex embedded nanoscale structures at the atomic scale.

We designed, fabricated and tested gallium phosphide (GaP) nano-waveguides for second harmonic generation (SHG). We demonstrate SHG in the visible range around 655 nm using modal phase matching. We observe phase matched SHG for different combinations of interacting modes by varying the widths of the waveguides and tuning the wavelength of the pump. We achieved a normalized internal SHG conversion efficiency of 0.4% W−1cm−2 for a continuous-wave pump at wavelength of 1283.5 nm, the highest reported in the literature for a GaP waveguide. We also demonstrated temperature tuning of the SHG wavelength with a slope of 0.17 nm/°C. The presented results contribute to the development of integrated photonic platforms with efficient nonlinear wave-mixing processes for classical and quantum applications.

Broadband solar light harvesting plays a crucial role for efficient energy conversion. Anapole excitations and associated absorption engineering in dielectric nanoresonators are a focus of nanophotonic research due to the intricate combination of nonradiating modes and strong electromagnetic field confinement in the underlying material. The arising high field strengths are used for enhanced second-harmonic generation and photocatalysis, where devices require large areas with closely spaced nanoresonators for sizable photonic yields. However, most anapole studies have so far been carried out at the single-particle level, neglecting the influence of anapole–anapole interactions. Here, we present a systematic study of coupling mechanisms in rectangular arrays of amorphous GaP nanodisks that support anapole excitations at 600 nm, which is within the lossy spectral regime of the material. Our experimental findings show that maximum visible light extinction by the array and maximum absorption in the GaP are not achieved by the densest packing of resonators. Counterintuitively, increasing the array periodicities such that collective effects spectrally overlap with the anapole excitation of a single particle leads to an absorption enhancement of up to 300% compared to a single disk. An analysis of coupling in one- and two-dimensional arrays with polarization-dependent measurements and numerical simulations allows us to discriminate between coupling interactions parallel and perpendicular to the polarization axis and evaluate their strengths. Utilizing a multipolar decomposition of excitations in single nanodisks embedded in one-dimensional arrays, we can attribute the coupling to enhanced electric and toroidal dipoles under variation of the interparticle spacing. Our results provide a fundamental understanding of tailored light absorption in coupled anapole resonators and reveal important design guidelines for advanced metasurface approaches in a wide range of energy conversion applications.

Part 1 Phenomenological description: introduction the photovoltaic effect and photoelectric phenomena linear and circular photovoltaic effects polarization aspects of the photovoltaic effect in some crystal types glass coefficients spatially oscillating and steady currents photoinduced fields experiment the magnetophotovoltaic effect conversion efficiency limits to the phenomenological description. Part 2 Principles of the microsopic theory: elementary-process asymmetry basic kinetic-theory formulas for a medium lacking a centre of symmetry the photovoltaic effect in impurity-band transitions band-band transitions shift PVE the scope for nondissipative current flow magnetic-field effects hop mechanism mechanisms related to spatial inhomogeneity. Part 3 The photovoltaic effect in particular materials: gallium arsenide gallium phosphide zinc sulfide tellurium quartz sillenites lithium niobate and tantalate potassium niobate barium titanate lead germanate barium-strontium niobate antimony sulfoiodide other materials. Part 4 Nonlinear optical phenomena due to the photovoltaic effect: the photorefractive effect holographic gratings two-beam coupling photoinduced scattering four-wave mixing. Part 5 Anomalous photoinduced fields: strong fields charge-stransport model hot-electron diffusion charge transfer in a light-induced grating. Part 6 Phenomena related to PVE: the photothermal effect relaxation currents even electrical and thermal conductivities absolute negative photoconductivity the surface photovoltaic effect mirror isomer separation.

Supercontinuum generation in bulk media is not normally observed at the nJ-level pulse energies available from high-repetition-rate femtosecond oscillators. Here, we present results demonstrating how a visible supercontinuum can be produced in bulk orientation-patterned gallium phosphide from 100-MHz 1040-nm femtosecond pulses with energies of up to 32 nJ. High-order parametric gain near 550 nm, seeded by self-phase-modulated spectral sidebands, underpins this new and simple supercontinuum process which yields an output spectrum spanning from the blue/green to the red.

This research is focused on the study and characterization of gallium phosphide based nanowires optical properties. Samples were grown by molecular beam epitaxy on Si (111) substrate and transferred to Menzel’s slide for optical measurements. Two different samples containing core-shell and axially heterostructured nanowires are studied. Analysis of the photoluminescence spectra demonstrate that depending on the NW geometry it can act as a Fabry-Perot cavity and provide good waveguiding properties. Emission spectra of the nanowires demonstrate high resistance to the excitation power. Investigation of the core-shell nanowire Raman spectra demonstrate shift of the TO mode with intense illumination due to possible strain effects induced by the temperature increase.

The nanoscale resistive switching characteristics of gallium phosphide (GaP) thin films directly grown on Si are investigated as a function of incident light. Firstly, as-grown GaP films show a high RON/ROFF (~10^4), shown to arise from the formation of conductive channels along the grain boundaries. It is proposed that point defects (most likely Ga interstitials) and structural disorder at the grain boundaries provide the ideal environment to enable the filamentary switching process. Next, we explored if such defects can give rise to mid-gap states, and if so could they be activated by photonic excitation. Both first-principles calculations as well as UV-vis and photoluminescence spectroscopy strongly point to the possibility of mid-gap electronic states in the polycrystalline GaP film. Photoconductive atomic force microscopy (phAFM), a scanning probe technique, is used to image photocurrents generated as a function of incident photon energy (ranging from sub band-gap to above band-gap) on the GaP film surface. We observe photocurrents even for incident photon energies lower than the band-gap, consistent with the presence of mid-gap electronic states. Moreover the photocurrent magnitude is found to be directly proportional to the incident photon energy with a concomitant decrease in the filament resistance. This demonstrates GaP directly integrated on Si can be a promising photonic resistive switching materials system., Comment: 23 pages, 6 figures

The mechanism of terahertz (THz) energy emission from gallium phosphide (GaP)-based avalanche transit time (ATT) sources has been discussed here. Six double-drift structured ATT devices based on GaP have been designed and optimized for operating at 0.1, 0.15, 0.2, 0.3, 0.5, and 1.0 THz frequencies. The large-signal results show that the THz performance of GaP ATT sources is more promising than the ATT oscillators based on conventional semiconductors.

Gallium phosphide is a nonlinear crystal of growing importance for integrated photonics. We observe and characterize a simultaneous second harmonic generation and third harmonic generation in a gallium phosphide microdisk for the first time.

Orientation-patterned gallium phosphide [1] (OPGaP) is a wide-bandgap material enabling two-photonabsorption-free pumping using 1040-nm Yb-lasers, and such OPGaP optical parametric oscillators (OPOs) have been applied in Fourier-transform [2] and dual-comb [3] spectroscopies across the 5–12-μm molecular fingerprint region. Hetero-epitaxial growth of GaP on orientation-patterned gallium arsenide (OPGaAs) templates has been developed [4] , to mitigate issues with GaP substrates, but no nonlinear frequency conversion has yet been demonstrated. Here we report the first efficient frequency conversion in OPGaP-on-OPGaAs. OPGaP layers up to 1.2-mm thick were grown by hydride vapor-phase epitaxy (HVPE) on a 3-inch MBE-grown OPGaAs template. Several multi-grating and fan-out crystals of lengths 1.1 mm and 2.9 mm were diced from the wafer and polished into plane-parallel chips, and a broadband anti-reflection coating was applied to both faces.

Gallium phosphide (GaP) is an ideal candidate to implement a III-V nucleation layer on a silicon substrate. The optimization of this nucleation has been pursued for decades, since it can form a virtual substrate to grow monolithically III-V devices. In this work we present a GaP nucleation approach using a standard MOVPE reactor with regular precursors. This design simplifies the epitaxial growth in comparison to other routines reported, making the manufacturing process converge to an industrial scale. In short, our approach intends to mimic what is done to grow multijunction solar cells on Ge by MOVPE, namely, to develop a growth process that uses a single reactor to manufacture the complete III-V structure, at common MOVPE process temperatures, using conventional precursors. Here, we present the different steps in such GaP nucleation routine, which include the substrate preparation, the nucleation itself and the creation of a p-n junction for a Si bottom cell. The morphological and structural measurements have been made with AFM, SEM, TEM and Raman spectroscopy. These results show a promising surface for subsequent III-V growth with limited roughness and high crystallographic quality. For its part, the electrical characterization reveals that the routine has also formed a p-n junction that can serve as bottom subcell for the multijunction solar cell. This work was supported by the Spanish Ministerio de Ciencia e Innovación through project VIGNEMALE [grant number RTI2018-094291-B-I00] and DAMAINSOL [grant number RTI2018-101020-B-I00].

There are few materials that are broadly used for fabricating optical metasurfaces for visible light applications. Gallium phosphide (GaP) is a material that, due to its optical properties, has the potential to become a primary choice but due to the difficulties in fabrication, GaP thin films deposited on transparent substrates have never been exploited. In this article we report the design, fabrication, and characterization of three different amorphous GaP metasurfaces obtained through sputtering. Although the material properties can be further optimized, our results show the potential of this material for visible applications making it a viable alternative in the material selection for optical metasurfaces.

We present the first temperature-dependent refractive index measurements of Gallium Phosphide (GaP) for a broad THz bandwidth extending to 4 THz and a wide temperature range from 77 K to 500 K. Our results show no significant degradation in velocity matching at cryogenic temperatures compared to room temperature. These measurements are critical for future average power and bandwidth scaling of optical rectification in GaP using kW-class excitation.

During the last decade, second harmonic generation (SHG) in III-V semiconductor microdisks has been demonstrated to be an efficient way to achieve frequency conversion with compact devices. Optimized coupling of both wavelengths to these devices still remains challenging. Here we study the impact of the coupling parameters on the SHG with vertical coupling between integrated waveguides and a III-V microdisk resonator.

Nanophotonics based on high refractive index dielectrics relies on appreciable contrast between the indices of designed nanostructures and their immediate surrounding, which can be achieved by the growth of thin films on low-index substrates. Here we propose the use of high index amorphous gallium phosphide (a-GaP), fabricated by radio-frequency sputter deposition, on top of a low refractive index glass substrate and thoroughly examine its nanophotonic properties. Spectral ellipsometry of the amorphous material demonstrates the optical properties to be considerably close to crystalline gallium phosphide (c-GaP), with low-loss transparency for wavelengths longer than 650 nm. When nanostructured into nanopatches, the second harmonic (SH) response of an individual a-GaP patch is characterized to be more than two orders of magnitude larger than the as-deposited unstructured film, with an anapole-like resonant behavior. Numerical simulations are in good agreement with the experimental results over a large spectral and geometrical range. Furthermore, by studying individual a-GaP nanopatches through non-degenerate pump-probe spectroscopy with sub-10 fs pulses, we find a more than 5% ultrafast modulation of the reflectivity that is accompanied by a slower decaying free carrier contribution, caused by absorption. Our investigations reveal a potential for a-GaP as an adequate inexpensive and CMOS-compatible material for nonlinear nanophotonic applications as well as for photocatalysis. Fil: Tilmann, Benjamin. Ludwig Maximilians Universitat; Alemania Fil: Grinblat, Gustavo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Berté, Rodrigo. Ludwig Maximilians Universitat; Alemania Fil: Özcan, Mehmet. Ludwig Maximilians Universitat; Alemania Fil: Kunzelmann, Viktoria F.. Technische Universitat München; Alemania Fil: Nickel, Bert. Ludwig Maximilians Universitat; Alemania Fil: Sharp, Ian D.. Ludwig Maximilians Universitat; Alemania Fil: Cortés, Emiliano. Ludwig Maximilians Universitat; Alemania Fil: Maier, Stefan A.. Ludwig Maximilians Universitat; Alemania Fil: Li, Yi. Southern University Of Science And Technology; China

A crystalline gallium phosphide nanodisk is shown to be the most efficient sub–100-fs nanoscale all-optical switch., High–refractive index nanostructured dielectrics have the ability to locally enhance electromagnetic fields with low losses while presenting high third-order nonlinearities. In this work, we exploit these characteristics to achieve efficient ultrafast all-optical modulation in a crystalline gallium phosphide (GaP) nanoantenna through the optical Kerr effect (OKE) and two-photon absorption (TPA) in the visible/near-infrared range. We show that an individual GaP nanodisk can yield differential reflectivity modulations of up to ~40%, with characteristic modulation times between 14 and 66 fs, when probed at the anapole excitation (AE). Numerical simulations reveal that the AE represents a unique condition where both the OKE and TPA contribute with the same modulation sign, maximizing the response. These findings highly outperform previous reports on sub–100-fs all-optical switching from resonant nanoscale dielectrics, which have demonstrated modulation depths no larger than 0.5%, placing GaP nanoantennas as a promising choice for ultrafast all-optical modulation at the nanometer scale.

Solid-state defect qubit systems with spin-photon interfaces show great promise for quantum information and metrology applications. Photon collection efficiency, however, presents a major challenge for defect qubits in high refractive index host materials. Inverse-design optimization of photonic devices enables unprecedented flexibility in tailoring critical parameters of a spin-photon interface including spectral response, photon polarization, and collection mode. Further, the design process can incorporate additional constraints, such as fabrication tolerance and material processing limitations. Here, we design and demonstrate a compact hybrid gallium phosphide on diamond inverse-design planar dielectric structure coupled to single near-surface nitrogen-vacancy centers formed by implantation and annealing. We observe up to a 14-fold broadband enhancement in photon extraction efficiency, in close agreement with simulations. We expect that such inverse-designed devices will enable realization of scalable arrays of single-photon emitters, rapid characterization of new quantum emitters, efficient sensing, and heralded entanglement schemes.

Long-distance fiber-based quantum communication relies on efficient non-classical light sources operating at telecommunication wavelengths. Semiconductor quantum dots are promising candidates for on-demand generation of single photons and entangled photon pairs for such applications. However, their brightness is strongly limited due to total internal reflection at the semiconductor/vacuum interface. Here we overcome this limitation using a dielectric antenna structure. The non-classical light source consists of a gallium phosphide solid immersion lens in combination with a quantum dot nanomembrane emitting single photons in the telecom O-band. With this device, the photon extraction is strongly increased in a broad spectral range. A brightness of 17 % (numerical aperture of 0.6) is obtained experimentally, with a single photon purity of g ( 2 ) ( 0 ) = 0.049 ± 0.02 at saturation power. This brings the practical implementation of quantum communication networks one step closer.