Porous Gallium Research Articles

Porous GaP/g‐C3N4 Photoanode for Enhanced Hydrogen Production

AbstractThe g‐C3N4 decorated porous gallium phosphide have been fabricated by a facile electrophoretic deposition (EPD) process. The morphology, element composition and light absorption of the GaP/g‐C3N4 photoanode were observed using field‐emission scanning electron microscopy, X‐ray photoelectron spectroscopy, ultraviolet and visible spectrophotometer, respectively. When acting as photoanode, porous GaP/g‐C3N4 serves as a direct Z‐scheme system, where photogenerated holes in GaP are expended by electrons generated from the g‐C3N4, inhibiting the corrosion of GaP. Therefore, the porous GaP/g‐C3N4 showed a larger photocurrent density, which is 2.1 times as large as that of the porous GaP without g‐C3N4, and a more stable photocurrent density for over 10000 s (at 0 V vs RHE). Thus, this work delivers a practical way to improve the photoelectrochemical stability and property of III–V semiconductor materials, which could be used in solar energy conversion fields.

Investigation of the Impact of Crystalline Arsenolite Oxide Formations on Porous Gallium Arsenide

Herein, the impact of arsenolite oxide (As2O3) crystallites on the structural and optical properties of porous gallium arsenide (GaAs) is examined, focusing on understanding the potential passivation effect and its influence on material stability and safety. Utilizing a comprehensive set of analytical methods, including cathodoluminescence (CL) spectroscopy, Raman scattering spectroscopy, and X‐ray diffraction, the interaction between the GaAs substrate and arsenolite crystallites is characterized. The results indicate that the crystallites do not significantly alter the electronic and optical properties of the underlying GaAs, suggesting a possible passivating effect that could enhance device performance. However, concerns regarding arsenolite's environmental stability and toxicity prompt a cautious approach to its application. Herein, the need for further research into conditions conducive to natural oxide formation, exploration of alternative passivation strategies, and development of safe and stable oxide layers is underscored. Reproducible results are necessary to confirm the differences in CL signals between samples, as the current findings are based on single measurements.

USE OF POROUS LAYERS OF GALLIUM ARSENIDE AS ATOMIC HYDROGEN SENSORS

The modern development of nanotechnologies, gadgets, and robotics is closely related to the use of nanosized particles of metals, dielectrics, and semiconductors. Composite heterosystems based on semiconductors are used in the creation of advanced opto- and nanoelectronic devices. The operation of such devices is based on the phenomena of excitation of the electronic subsystem of the conductor. The paper investigates the occurrence of non-equilibrium chemiconductivity in gallium arsenide (GaAs) samples when the sample surface is in contact with atomic hydrogen. The effect occurs due to the non-thermal generation of electron-hole (e–h) pairs in the semiconductor wafer, thanks to the energy released during the chemical interaction of hydrogen atoms with the GaAs surface (adsorption and recombination of atoms with the formation of H2 molecules). The kinetics of chemiconductivity was studied, as well as the dependence of chemiconductivity on the density of the flow of atoms per sample and temperature. It was found that the process of generation of (e–h) pairs involves both acts of adsorption of atoms and acts of recombination of atoms into a molecule. The revealed effect of the appearance of non-equilibrium conductivity in samples of single-crystal gallium arsenide during recombination on the surface of atomic hydrogen clearly indicates the presence of effective channels for the accommodation of chemical energy by the conductor when a chemical reaction occurs on its surface. To increase the sensitivity of such a sensor by increasing the area of the "active" surface, it is proposed to use a porous layer of GaAs (por-GaAs). The phenomenon of non-equilibrium chemiconductivity in porous gallium arsenide, discovered and investigated for the first time in this paper, opens up wide prospects for the use of this semiconductor for the direct conversion of chemical energy into electrical energy. Semiconductors with a narrow bandgap of this type have prospects in the development of devices for the direct conversion of chemical energy into electrical energy, as well as in the creation of chemical sensors. The possibility of using this material as a detector of hydrogen atoms in the gas phase is substantiated.

Nanoporous GaN Photoanode Decorated with Plasmonic Au Nanoparticles for Enhanced Solar Water Splitting

Photoelectrochemical (PEC) water splitting is a promising approach to generating eco‐friendly hydrogen energy from water. Despite long‐lasting efforts, the existing methods still suffer limitations in the design of photoelectrodes with optimal structures for efficient operation. Herein, a novel porous gallium nitride (PGaN) photoanode decorated with plasmonic Au nanoparticles (AuNPs) is fabricated. After microstructural optimization, this composite photoanode improves the water‐splitting efficiency from 0.036% to 0.30% and exhibits a 2.7 times improvement of the photocurrent density in comparison with the planar GaN photoanode. The significant improvement of the water‐splitting efficiency is attributed to the synergistic combination of the porous structure with the plasmonic AuNPs that greatly benefits electron–hole pairs generation, separation, and charge‐carrier transport. The photoanode is robust and easy to fabricate, and this work provides an idea for future exploration of durable and efficient GaN‐based photoelectrodes.

Biophotonic sensor design for the detection of reproductive hormones in females by using a 1D defective annular photonic crystal

Abstract In this research work, we have proposed a one-dimensional (1D) defective annular photonic crystal (DAPC) (AB)5 CDC(AB)5 to identify the presence of reproductive progesterone and estradiol hormones in women. The periodicity of the proposed biosensing design made up of 1D annular photonic crystal (APC) has been broken by introducing a cylindrical cavity D of porous gallium nitride (GaN) material. The inner and outer faces of cylindrical cavity D are surrounded by concentric cylindrical buffer layers of magnesium fluoride (MgF2) material. We have used a modified transfer matrix method with the help of MATLAB software to carry out investigations pertaining to the proposed theoretical work. The two distinct categories of blood samples containing reproductive hormones of different concentrations have been used in this work. The sensitivity of proposed 1D DAPC varies between 159.673 nm nmol−1 L−1 to 170.1525 nm nmol−1 L−1 when a cavity is infiltrated with a blood sample having progesterone hormone whose concentration varies between 0 and 200 nmol L−1. Moreover, the sensitivity of the structure varies between 158.7816 nm nmol−1 L−1 to 170 nm nmol−1 L−1 under the influence of blood samples having estradiol hormones of different concentrations. In order to evaluate the performance of the proposed biosensor in the true sense we have also computed quality factor (Q) and figure of merit (FoM) values of the biosensor corresponding to both categories of blood samples of different concentrations. Our study shows that biosensors made up of 1D annular photonic structures are more efficient in comparison to the biosensors made up of planar 1D photonic crystals. Apart from detecting the reproductive hormones in females such kind of APC-based specialized biosensing devices may be very useful in the field of medical engineering and technology.

Synthesis of porous γ-gallium oxide films using refrigerator aging oxidation from gallium nanoparticles

Porous gallium oxide films were tried to synthesize at low temperatures. Ga nanoparticle dispersions were synthesized using ultrasound irradiation in 2-propanol and two films methods were considered. In the case of the spray coating of Ga nanoparticle dispersions and treatment with hydrazine vapor, Ga films were obtained. In the case of depositing Ga nanoparticles on a cover glass and aging them in hydrazine solution at a refrigerator temperature, porous γ-Ga2O3 film was synthesized. This new process of low-temperature aging in a refrigerator using hydrazine solution allows synthesizing porous γ-Ga2O3 film. Generally, the synthesis of oxide ceramics requires high-temperature processing, but this method allows oxidation at low temperatures, such as refrigerator temperatures, making it an energy-efficient process.

Obtaining gallium nitride cluster for information transmission in optoelectronic communication lines

The paper proposes a method for obtaining light-emitting clusters of gallium nitride (GaN) on porous gallium arsenide (GaAs) substrates by treating the substrate with nitrogen atoms from a nitrogen RF plasma. The morphological and luminescent properties of the obtained structures were studied. Reasons for the possibility of using light-emitting GaN clusters for the manufacture of LEDs and their use in optoelectronic communication lines are provided. It was established that the photoluminescent properties of GaN clusters depend on the porosity of the GaAs substrate and the geometric dimensions of the formed clusters.

Electrical conductivity through π-π stacking in a two-dimensional porous gallium catecholate metal-organic framework.

Metal-organic frameworks (MOFs) are hybrid materials known for their nanoscale pores, which give them high surface areas but generally lead to poor electrical conductivity. Recently, MOFs with high electrical conductivity were established as promising materials for a variety of applications in energy storage and catalysis. Many recent reports investigating the fundamentals of charge transport in these materials focus on the role of the organic ligands. Less consideration, however, is given to the metal ion forming the MOF, which is almost exclusively a late first-row transition metal. Here, we report a moderately conductive porous MOF based on trivalent gallium and 2,3,6,7,10,11-hexahydroxytriphenylene. Gallium, a metal that has not been featured in electrically conductive MOFs so far, has a closed-shell electronic configuration and is present in its trivalent state-in contrast to most conductive MOFs, which are formed by open-shell, divalent transition metals. Our material, made without using any harmful solvents, displays conductivities on the level of 3 mS/cm and a surface area of 196 m2 /g, comparable to transition metal analogs.

Hierarchically porous GaN thin films fabricated using high fluence Ar ion implantation of epitaxial GaN on sapphire

• We show the fabrication of hierarchical pores in GaN by means of Ar ion implantation. • This approach is free of the limitations of anodic etching of porous GaN. • There is no need for uniform current spreading to obtain uniform porosity. • The submission focuses on the material properties not on the implantation process. • We demonstrate different damage behavior for single and double ionized Ar. We show a method to fabricate porous gallium nitride (GaN) films without the need for wet chemical etching nor high donor concentrations in the starting material. The pores in epitaxial GaN films were formed using 200 keV Ar + ion implantation at fluences ranging from 2.5∙10 16 Ar + ∙cm −2 to 10 17 Ar + ∙cm −2 . The properties of the created nanostructures are discussed by means of complementary structural, optical and electrical studies. Electrochemical capacitance of the samples in an aqueous electrolyte is studied to deconvolute information about the surface area available after the implantation. Single and double ionized implantation is compared in the discussion and different damage in the two cases is shown. The results show information complementary to the current models of damage buildup in gallium nitride films upon high fluence irradiation as well as present a means of fabricating on-wafer porous areas for future GaN-based devices. The method overcomes the drawbacks of the commonly applied anodic etching: it does not require a high GaN donor concentrations nor difficult setups for achieving uniform etching. Furthermore, it can be applied locally using appropriate masking of the selected areas with a thick photoresist or other strippable inorganic ion stopping film.

Fabrication of porous gallium nitride (GaN) utilizing two-step etching method and control of its optical properties

Fabrication of porous gallium nitride (GaN) utilizing two-step etching method and control of its optical properties

РОЗРОБКА ПРОГРАМНОГО ЗАБЕЗПЕЧЕННЯ ДЛЯ ІНФОРМАЦІЙНО-УПРАВЛЯЮЧОЇ СИСТЕМИ ВИРОЩУВАННЯМ АРСЕНІДУ ГАЛІЮ ДЛЯ ПОРУВАТИХ ПІДКЛАДОК

Purpose. The article discusses the features of improving the technology of growing gallium arsenide ingots for the production of substrates that are intended for applying a porous film. Such porous gallium arsenide is used to manufacture gas sensors with improved technical parameters. Such sensors are highly sensitive and can operate at room temperature without the use of heating systems. To improve the technology of growing gallium arsenide ingots, the paper proposes the development of software for an information-control system for growing ingots. The features of the technological process of growing gallium arsenide ingots are considered in detail and the main parameters that directly affect the process are analyzed. Based on the analysis, the requirements for the operation algorithm of the information and control system have been developed. Methodology. The developed algorithm allows organizing the system operation in three modes; Technologist mode, operator mode, adjuster mode. Each mode has its own privileges and its own limitations. In addition, the algorithm allows organizing control and output of information from the following subsystems: heater control subsystem, crucible control subsystem, seed control subsystem, weight sensor control subsystem, as well as storing information in the database. Results. Software has been developed that implements this algorithm. The technologist mode is designed to form the growth profile of ingots. The technologist can choose one of the existing profiles previously recorded with reference to the ingot brand, or create a new profile in case of launching a new batch of products. The profile allows you to bind changes in technological parameters to the length of the ingot. In the "Operator" mode, the system displays current information about the technological process and allows you to organize work in automatic or manual mode. Manual mode is designed to adjust the process parameters in case of emergency situations. In the “Adjuster” mode, it is possible to configure the control system depending on specific requirements, change the PID controller coefficients, and configure input and output signals. Originality. The proposed program differs from the existing ones in that it allows you to freely configure the control system for the growth of gallium arsenide ingots, in particular, to change the parameters with reference to the length of the grown ingot or to the diameter of the ingot. Change the parameters of the inputs and outputs of the controllers. Practical value. The developed system makes it possible to improve the quality of gallium arsenide ingots by eliminating the human factor, which often leads to process parameters going beyond acceptable values, to increase the repeatability of ingot parameters, and to obtain better substrates for manufacturing gas sensors. The proposed software can be used for the system of growing silicon ingots in the electronics industry. Figures 4, references 14.

Infrared reflectance characterization of porous GaN thin films on sapphire substrate using factorized-Rayleigh model

The surface morphology dependence of porous gallium nitride (PGaN) thin film on infrared (IR) dielectric response was investigated using s-polarized IR reflectance technique. Porosity-induced resonances, namely, Fröhlich modes, were observed in the reststrahlen region of PGaN. Several phenomenological effective medium theories (EMTs), i.e., Maxwell Garnett, Bruggeman, Looyenga, Lichtenecker, and Rayleigh (Ra) models, were used to simulate the dielectric function and Fröhlich modes of PGaN. Among the EMTs, only the Ra model successfully predicts all resonant features that originated from Fröhlich modes. Finally, the Ra model is reformulated in factorized form to take into account the damping of Fröhlich modes and Fröhlich-plasmon coupling. Given the good fitness of experimental and simulated spectra and with the reasonable prediction of Fröhlich modes, factorized-Ra model is determined to be the most appropriate EMT to describe the IR dielectric response of PGaN with cylindrical air hole.

Electrodeposition of Pd-Pt Nanocomposites on Porous GaN for Electrochemical Nitrite Sensing.

In recent years, nitrite pollution has become a subject of great concern for human lives, involving a number of fields, such as environment, food industry and biological process. However, the effective detection of nitrite is an instant demand as well as an unprecedented challenge. Here, a novel nitrite sensor was fabricated by electrochemical deposition of palladium and platinum (Pd-Pt) nanocomposites on porous gallium nitride (PGaN). The obtained Pd-Pt/PGaN sensor provides abundant electrocatalytic sites, endowing it with excellent performances for nitrite detection. The sensor also shows a low detection limit of 0.95 µM, superior linear ampere response and high sensitivity (150 µA/mM for 1 to 300 µM and 73 µA/mM for 300 to 3000 µM) for nitrite. In addition, the Pd-Pt/PGaN sensor was applied and evaluated in the determination of nitrite from the real environmental samples. The experimental results demonstrate that the sensor has good reproducibility and long-term stability. It provides a practical way for rapidly and effectively monitoring nitrite content in the practical application.

Photodeposition of palladium nanoparticles on a porous gallium nitride electrode for nonenzymatic electrochemical sensing of glucose.

A nonenzymatic electrochemical glucose sensor is described that was obtained by in situ photodeposition of high-density and uniformly distributed palladium nanoparticles (PdNPs) on a porous gallium nitride (PGaN) electrode. Cyclic voltammetric and chronoamperometric techniques were used to characterize the performance of the modified electrode toward glucose. In 0.1 M NaOH solution, it has two linear detection ranges, one from 1μM to 1mM, and another from 1 to 10mM, and the detection limit is 1μM. The electrode is repeatable, highly sensitive, fast and long-term stable. It was applied to the quantitation of serum glucose where it displayed accurate current responses. Graphical abstract A novel nonenzymatic electrochemical glucose sensor was developed by in situ photodeposition of palladium nanoparticles on the porous gallium nitride electrode.

Communication—Anisotropic Electrochemical Etching of Porous Gallium Nitride by Sub-Bandgap Absorption Due to Franz-Keldysh Effect

Anisotropic electrochemical etching of porous GaN structures by utilizing charge carriers generated by sub-bandgap absorption has been developed. Sub-bandgap light with a photon energy below the bandgap energy was transmitted through bulk GaN, but a certain type of photo-absorption additively occurred at the pore tip due to the Franz-Keldysh effect. The photocurrents observed when the reverse bias was applied to n-GaN were well reproduced by calculation taking into account the Frantz-Keldysh effect. The pore diameter was not changed that much, but the pore depth could be successfully controlled by the intensity and irradiation time of the sub-bandgap light.

Effect of Conditions of Electrochemical Etching on the Morphological, Structural, and Optical Properties of Porous Gallium Arsenide

Effect of Conditions of Electrochemical Etching on the Morphological, Structural, and Optical Properties of Porous Gallium Arsenide

(Invited) Electrochemical Formation and Application of Porous Gallium Nitride

Gallium nitride (GaN), which is a III-V compound semiconductor, has wide direct bandgap (3.4 eV), high breakdown electric field (3.3x106 V/cm) and high saturation electron velocity (2.7 x107 cm/sec). On the basis of excellent optical and electrical properties, significant progress has been achieved in the GaN-based devices, such as ultraviolet laser diodes, white light-emitting diodes, high electron mobility transistors (HEMTs), and high-power FETs. In addition, GaN and its alloys are getting much attention as building block materials for electrochemical (EC) energy conversion systems such as chemical sensors, water splitting, and artificial photosynthesis due to their superior chemical stability, direct transition, and widely tunable bandgap by alloying. Among the various techniques for improving their conversion efficiency, porosification utilizing EC reactions is one of the most powerful because a high-density array of pores exhibits high specific surface area, low reflectance, and high absorptance properties. In addition, this technique is performed at room temperature and does not require any complicated process such as lithography, indicating lower damage and higher productivity than other nanostructure fabrication techniques such as reactive ion etching and selective-area growth. In this presentation, we review our recent work on the fabrication of porous GaN utilizing various EC techniques and their applications [1-3]. One example is the two-step process combining EC etching process with conventional chemical etching process. EC etching was first performed in the dark condition using an aqueous electrolyte consisting of H2SO4 and H3PO4. Wet chemical etching was subsequently conducted in 25 % tetramethylammonium hydroxide (TMAH) at 90°C. The porous structure formed by the first EC etching has straight pores oriented perpendicular to the top surface. Pore depth linearly increased with EC etching time, indicating that superior depth control was achieved. This behavior can be explained as resulting from anisotropy of the EC etching. Namely, the etching reaction proceeded only to the direction belong to the high-electric field induced by the anodic voltage. On the other hand, the pore diameter kept a constant value throughout the EC etching and could not be controlled by the EC etching time. However, the pore diameter could be changed by wet chemical etching utilizing TMAH as subsequent treatment after the EC etching. By applying TMAH etching, pore shape changed from a round to a hexagonal shape surrounded with 6 facets of {1−100}. In addition, the pore diameter estimated from SEM observation increased linearly with the TMAH etching time, whereas the pore depth was unchanged. These results indicate that TMAH etching proceeds anisotropically in the horizontal direction, but not in the vertical direction of the substrate. The optical and photoelectrochemical properties of porous GaN were very sensitive to the structural properties. From the photoluminescence (PL) measurements, the intensity of yellow luminescence (YL) related to high-density point defects was drastically decreased by the formation of porous structures, suggesting that gallium vacancy (V Ga) related defects were preferentially removed by EC etching. Photoreflectance measurement revealed that porous sample had an effective refractive index that could be controlled by TMAH etching time. In photoelectrochemical measurement, the incident-photon-to-current conversion efficiency (IPCE) was dramatically enhanced by the formation of porous structures. A series of experimental results were consistently explained by the change of thickness of pore wall with a width of space charge region. These results suggest that precise structural controlling is crucially important to obtain superior capability for EC energy conversion systems, and the two-step process utilizing anisotropic EC etching and TMAH etching is very promising as a nanostructure fabrication technique. Acknowledgement: This work was supported by JSPS KAKENHI - JP15K13937，JP16H06421，JP17H03224. A. Watanabe et al., ECS Electrochem. Lett., 4, H11 (2015).Y. Kumazaki et al., J. Electrochem. Soc., 164, H477 (2017).M. Toguchi et al., 233rd ECS Meeting, Z01-2550, Seattle, WA, 15 May (2018).

(Invited) Electrochemical Formation and Application of Porous Gallium Nitride

This article provides an overview of our recent work on the formation and application of porous GaN. The photo-assisted electrochemical process in back-side-illumination mode, compared with front-side-illumination mode, has been demonstrated to form deeper pores where illumination with photon energy below the bandgap plays an important role. Electrochemical etching by using the avalanche effect in the dark was very effective in controlling the pore depth with an anodization time. Precise control of pore diameter was achieved by subsequent wet chemical etching after the formation of porous GaN. Photoelectrochemical measurements revealed the importance of precise structural controlling of porous GaN for application to energy-conversion systems.

Fabrication and photoluminescence performance of porous gallium nitride luminescent materials using different 1-ethyl-3-methylimidazolium-based ionic liquids

Porous gallium nitride (GaN) luminescent materials were fabricated by photoelectrochemical etching using three different 1-ethyl-3-methylimidazolium ([EMIM])-based ionic liquids as the etchants. The as-etched porous GaN presents honeycomb shape, deep gully with some holes in the surroundings, and overlapping hole structure, which are significantly different from the planar GaN. Moreover, photoluminescence (PL) spectra indicates that the porous GaN has more excellent PL performance than the planar GaN. In general, reducing the etching time to 1 min, the PL intensity of porous GaN etched by [EMIM][OTF] is 9.27 times than that of the planar one. These results suggest that porous GaN etched by ionic liquid can be an outstanding substrate in the field of the luminescent material.

Investigation of the porous GaP layers' chemical composition and the quality of the tests carried out

Purpose: The purpose of this study is to establish the quality of tests for determining the chemical composition of the porous surface obtained by the method of electrochemical etching, based on the indicators of convergence and reproducibility of the results. Design/methodology/approach: The method of electrochemical etching was used to obtain layers of porous gallium phosphide, which can be used as buffer layers for nitrides formation on their basis. Por-GaP was formed in a solution of hydrofluoric acid at a current density of j =100 mA/cm2, etching was carried out for 20 minutes. The resulting structures sulfide passivation was carried out, thus avoiding the formation of an oxide film on the samples surfaces. For this purpose, porous gallium phosphide samples were kept in a sulfide solution for 10 minutes and dried in a stream of nitrogen. The chemical composition of the porous GaP surface layers has been investigated. To do this, the method of electronprobe INCA Energy microanalysis was used. The research was carried out on the entire surface of the sample in order to calculate the total spectrum of the elemental composition of the sample under study. Findings: It was established that during anodizing, the stoichiometry of the crystals investigated did not shift significantly towards the excess of gallium atoms. Oxygen is present at an insignificant concentration of 0.3%. This indicates the effectiveness of conducting the sulfide passivation of the sample surface following the electrochemical treatment. The presence of fluorine atoms that appeared on the surface as a result of the reaction with the electrolyte during etching, is observed in extremely low concentration. Experimental studies have shown that the sample chosen can be used as a standard enterprise sample when analyzing the chemical composition of the surface of porous gallium phosphide due to its convergence, reproducibility, homogeneity. In addition, the given method for determining the standard sample can be applied to other porous semiconductors. Conducting such studies is an important technological task that will allow us to create a series of standard samples of porous semiconductors of A3B5 group. Research limitations/implications: The research was carried out for porous gallium phosphide samples synthesized in the solution of hydrofluoric acid, though, carrying out of similar experiments for por-GaP obtained in other conditions, is necessary. Practical implications: The studies of the reproducibility and convergence of the experiment have an important practical significance, since it is the reproducibility of the experiment results that is the main problem to modern material science, all the more to nanoengineering. Therefore, the technique proposed, will allow the synthesis of por-GaP layers with adjustable properties, will facilitate their widespread implementation in the real sectors of industry. The obtained porous layers can be used as standard samples. Originality/value: The main problem in the nanostructures synthesis is the adjustability of properties. The technique presented allows to form stable layers of the porous gallium phosphide with the surface chemical composition known in advance. In addition, carrying out the sulfide passivation allows to stabilize por-GaP properties, which is an important process task. For the first time, a study of the presented technique as to convergence, reproducibility and homogeneity, was conducted.