Gallium Arsenide Structures Research Articles

Anomaly Detection in the Molecular Structure of Gallium Arsenide Using Convolutional Neural Networks

This paper concerns the development of a machine learning tool to detect anomalies in the molecular structure of Gallium Arsenide. We employ a combination of a CNN and a PCA reconstruction to create the model, using real images taken with an electron microscope in training and testing. The methodology developed allows for the creation of a defect detection model, without any labeled images of defects being required for training. The model performed well on all tests under the established assumptions, allowing for reliable anomaly detection. To the best of our knowledge, such methods are not currently available in the open literature; thus, this work fills a gap in current capabilities.

The physical mechanism underpinning superfast switching of GaAs S-diode

Recently a physical phenomenon termed “collapsing field domains” (CFDs) was discovered, which manifests itself in several avalanching gallium arsenide (GaAs) structures. The phenomenon consists of the formation of a comb of ultra-high-amplitude field domains, which generate a dense electron-hole (e-h) plasma. Each domain surrounded by the plasma shrinks down to a nanometre scale in width, followed by collapse. Those domains cause different peculiar transient features from superfast (picosecond range) high-current avalanche switching in the voltage-blocking layers to sub-THz pulsed electromagnetic emission, filaments with extreme (∼10 MA/cm2) current density, hot-photon radiation, etc. The physics of those moving domains differs drastically from the Gunn effect having in common only a requirement of negative differential mobility (NDM) of the electrons and the fact that both phenomena have so far been observed in n-type GaAs layers. Here we demonstrate the CFD phenomenon in a p-layer formed by a deep acceptor. This finding contributes to the interpretation of superfast switching in so-called S-diodes. Besides proving the CFD nature underpinning superfast switching, we show the unique parameters of a simple, S-diode-based optical transmitter that achieves high-power (∼160 W) sub-nanosecond output. This performance is relevant to automotive and flight guidance applications of lidar. A brief review of alternative solutions presenting previous state-of-the-art for miniature lidar transmitters is given for comparison.

Формирование вертикального графена на поверхности арсенид-галлиевых структур

The properties of carbon layers (C- layers) formed by thermal decomposition of CCl4 at temperatures of 600–700°C on the surface of gallium arsenide structures fabricated by MOС-hydride epitaxy on n+-GaAs (100) wafers have been studied. The surface morphology of the carbon layers was studied using atomic force microscopy. The structural and optical properties were studied using Raman spectroscopy and reflection spectroscopy. It has been found that in the case of a C layer fabricated at a temperature of 650–700°C, the atomic force microscopy image demonstrates the presence of vertical carbon nanowalls (vertical graphene) located parallel to one of the [110] directions of the GaAs crystal lattice. The characteristics of the bands observed in the Raman spectra correspond to the parameters of the spectra of vertical graphene. The reflection coefficient of such carbon layers significantly decreases (diffuse reflection does not exceed 25% for a layer fabricated at 700°C) in the wavelength range from 0.19 to 1.8 μm. The presence of a significant "absorbing" ability makes the obtained carbon layers promising as a conducting contact in photosensitive semiconductor device structures, which is confirmed by preliminary results of studies of the current-voltage characteristics and spectral dependences of the photocurrent.

Formation of vertical graphene on surface of the gallium-arsenide structures

Formation of vertical graphene on surface of the gallium-arsenide structures

Studies of Be, Si doping regulated GaAs nanowires for phase transition and optical properties

GaAs-based semiconductor doping technology, in which impurity energy levels are introduced into the band gap, can give rise to a decisive effect on its electrical and optical properties. When GaAs material is reduced to one-dimensional nanoscale, due to the increase of specific surface area, wurtzite- zinc blende coexisting structure is prone to appearing. GaAs nanowire doping can not only adjust its electro-optical properties, but also have a significant regulatory effect on its structural phase transition. The effects of beryllium (Be) and silicon (Si) doping on crystal structure and optical properties of gallium arsenide (GaAs) nanowires (NWs) are studied in this paper. Primitive, Si-doped and Be-doped GaAs NWs are grown on Si(111) substrates by molecular beam epitaxy in virtue of the self-catalyzed growth mechanism. The Raman spectra of primitive, Si-doped and Be-doped GaAs NWs are measured. The E2 mode peak unique to the WZ structure of primitive GaAs NWs is found in the Raman spectrum, and the E2 mode peak in the Raman spectrum of Si-doped GaAs NWs weakens or even disappears. Moreover, The E2 mode peak is not found in the Raman spectrum of Be-doped GaAs NWs. Furthermore, the structural changes of GaAs NWs are observed more intuitively by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The PL spectra show that the wurtzite (WZ)-zinc blende (ZB) mixed phase II-type luminescence exists in primitive GaAs NWs, then the luminescence disappears due to Si or Be doping and turns into impurity defect related luminescence.

Investigation of 1.9 μm GINA Simulated as Intrinsic Layer in a GaAs Homojunction: From 25% Towards 32.4% Conversion Yield

Based on a PC1D (Personal Computer One-Dimensional) simulator device, we have investigated three solar prototypes of gallium arsenide structures labeled as SPI, SPII and SPIII, under AM1.5G condition at one sun irradiation. The PC1D simulation predicts 25% and 25.9% efficiency for n-p and n-i-p GaAs unit solar cells, which is comparable to the National Renewable Energy Laboratory (NREL) measurement (27.6% for 1 cm2 GaAs solar cell). An experimental investigation of 1.9 μm GaInNAs (GINA) through the photoluminescence (PL) technique shows that the investigated quaternary is promising for solar application (Eg = 1.2 eV). Therefore, the i-GINA film sandwiched between n-GaAs and p-GaAs semiconductors is numerically simulated for an area of 1 cm2. The insertion of a GINA layer increases the light-to-electricity yield to 32.4%. The other solar parameters of the cell prototypes are estimated as the following: $$ V_{\rm{oc}}^{{{\rm{SP}}_{\rm{I}} }} = 1.024\;{\hbox{V}} $$ , $$ J_{\rm{sc}}^{{{\rm{SP}}_{\rm{I}} }} = 32.04\;{\hbox{mA}}/{\hbox{cm}}^{2} $$ , FF = 70.7%, $$ V_{\rm{oc}}^{{{\rm{SP}}_{\rm{II}} }} = 1.004\;V $$ , $$ J_{\rm{sc}}^{{{\rm{SP}}_{\rm{II}} }} = 32.11\;{\hbox{mA}}/{\hbox{cm}}^{2} $$ and FF = 66.3% and $$ V_{\rm{oc}}^{{{\rm{SP}}_{\rm{III}} }} = 0.818\;{\hbox{V}} $$ , $$ J_{\rm{sc}}^{{{\rm{SP}}_{\rm{III}} }} = 32.42\;{\hbox{mA}}/{\hbox{cm}}^{2} $$ and FF = 70.2%. An optimization of GINA thickness for a 0.3 μm n-GaAs/4 μm p-GaAs junction consists of a 2.2 μm layer to achieve the highest photovoltaic yield η = 32.6%.

Phase-Matched Mid-Infrared Difference Frequency Generation Using a Nanostructured Gallium Arsenide Metamaterial With Nanoholes

Phase-matched wavelength conversion is achieved in difference frequency generation (DFG) in a structure of gallium arsenide (GaAs) with periodic arrays of nanoholes. Linear properties (refractive indices) of the structure are determined from the S -parameters of the structure. Finite difference time domain (FDTD) simulation is used to calculate the S -parameters. The longest wavelength achieved is 16.2229 μm and the shortest is 3.2961 μm. The results of the FDTD simulation are compared with results obtained from the effective medium theory by using the Maxwell Garnett model. The comparison shows excellent agreement.

Нелинейность вольт-амперных характеристик однородных компенсированных детекторных структур из GaAs

The paper presents the results of the study of charge carrier transport and deep level recharging in semiconductor structures for ionizing radiation detectors. The resistive gallium arsenide structures with Schottky barriers and a uniform distribution of the deep chromium acceptor and the deep EL2 donor centers were studied. The effect of depletion of the volume of detector structures with electrons has been found by solving the continuity and Poisson equations with the use of a commercial software. It is found that the nonlinearity of the current-voltage characteristics of the structures is associated with change in the conductivity type under transition from an equilibrium to a nonequilibrium state. In this case, the structures with the initial equilibrium p-type conductivity have current-voltage characteristics close to linear.

The Effect of the Composition of a Carrier Gas during the Growth of a Mn delta-Layer on the Electrical and Magnetic Properties of GaAs Structures

The effect of the arsine content (from 0 to 8 μmol), supplied to a reactor together with hydrogen, on the formation of delta-doped gallium-arsenide structures by the pulsed laser sputtering of a Mn target is investigated. It is found that an arsine molar fraction of ~2.5 μmol in the reactor atmosphere during the formation of a Mn delta-doped GaAs layer allows one to obtain single-crystal epitaxial structures with the lowest layer resistance and a ferromagnetic-paramagnetic phase transition temperature of about 40 K. Increasing the arsine content to 8 μmol or the absence of arsine in a hydrogen flow leads to a significant increase in the layer resistance in the temperature range below 150 K and a decrease in the Curie temperature. In the first case, this may be due to partial compensation of the hole conductivity by donor-type defects formed as a result of an excess of arsenic on the growing surface (arsenic atoms in Ga positions or in interstitial positions). In the second case, when no arsine is supplied to the reactor, the growth surface is likely to be enriched with gallium atoms, which makes the incorporation of Mn into the Ga sublattice difficult.

Findings show nanostructures can withstand high levels of strain while keeping photoluminescence

Dynamic compression experiments reveal that nanoscale gallium arsenide structures are able to suppress strain effects on function at pressures up to 2.6 gigapascals.

Magnetoelectric effect in a sandwich structure of gallium arsenide–nickel–tin–nickel

The results of investigation of the magnetoelectric effect in a nickel-tin-nickel sandwich structure obtained by galvanic deposition of gallium arsenide on a substrate are presented. The technology of constructing such structures is described and the experimental results of the frequency dependence of the effect are presented. It is shown that the use of tin as an intermediate layer reduces the mechanical stresses resulting from the incommensurability of the phases, which permits obtaining qualitative structures with the nickel thickness of about 70 μm. The resulting structures exhibit good adhesion between the layers and have a high quality factor.

Влияние состава газа-носителя в процессе роста дельта-слоя Mn на электрические и магнитные свойства GaAs-структур

AbstractThe effect of the arsine content (from 0 to 8 μmol), supplied to a reactor together with hydrogen, on the formation of delta-doped gallium-arsenide structures by the pulsed laser sputtering of a Mn target is investigated. It is found that an arsine molar fraction of ~2.5 μmol in the reactor atmosphere during the formation of a Mn delta-doped GaAs layer allows one to obtain single-crystal epitaxial structures with the lowest layer resistance and a ferromagnetic-paramagnetic phase transition temperature of about 40 K. Increasing the arsine content to 8 μmol or the absence of arsine in a hydrogen flow leads to a significant increase in the layer resistance in the temperature range below 150 K and a decrease in the Curie temperature. In the first case, this may be due to partial compensation of the hole conductivity by donor-type defects formed as a result of an excess of arsenic on the growing surface (arsenic atoms in Ga positions or in interstitial positions). In the second case, when no arsine is supplied to the reactor, the growth surface is likely to be enriched with gallium atoms, which makes the incorporation of Mn into the Ga sublattice difficult.

Capacitance spectroscopy of hole traps in high-resistance gallium-arsenide structures grown by liquid-phase epitaxy

Three deep acceptor levels with activation energies of ~0.7, ~0.41, and ~0.16 eV are found in GaAs structures, which have the hole type of conductivity and are grown by liquid-phase epitaxy, by the methods of capacitance spectroscopy (admittance spectroscopy and deep-level transient spectroscopy). The first two levels are known as HL2 and HL5 and are related to the features of GaAs-layer growth by liquid-phase epitaxy. They are effective recombination centers determining reverse currents in p–i–n diodes, which is confirmed by studying the temperature dependences of reverse currents. The level with the energy Ev + 0.16 eV can be related to the two-charge acceptor level of the inherent antisite defect in GaAs, which also determines the doping concentration of structures in the singly charged state.

Reflectivity modulator based on GaSb/GaAs heterostructure

A structure of gallium antimonide (GaSb) and gallium arsenide (GaAs) wafers is built to modulate light reflectivity at CO2 laser wavelength. A quantum well composed of GaSb/GaAs heterojunction with highly doped GaAs up to 3×1018 cm-3 is inserted inside a layer structure. A grating of periodic structure of GaAs and gold layer is added just below the substrate. Gsolver software is used to determine the reflectivity of incident light with the existence of free carriers. A voltage is applied to the doped layer to deplete the free electrons and the reflectivity is determined again. The significant difference in reflectivity between the two cases can be used to build a light reflectivity modulator device.

Research into constructive and technological features of epitaxial gallium-arsenide structures formation on silicon substrates

The technology of formation of LSI structures on GaAs epitaxial layers, formed on Si-substrates of large diameter, is developed, which makes it possible at least by an order of magnitude to reduce the production cost of crystals due to epitaxial growth of GaAs layers and the use of technological equipment of silicon technology. This technology also enables the useof heterostructures to increase the speed of the LSI. An analysis of complex structures of different architecture of IC/LSI on GaAs epitaxial layers, formed on Si-substrates, is carried out. The influence of the scattering processes of charge carriers on the potential fluctuations on the magnitude and profile of the mobility of electrons along the thickness of the epitaxial structure is investigated. When using epitaxial technology in structures, there are no isoconcentric impurities of oxygen and carbon, which are the factors of scattering of charge carriers, which makes it possible to achieve high values of mobility of charge carriers. It is shown that the use of epitaxial layers of gallium arsenide eliminates the effects of isoconcentration impurities of oxygen and carbon in gallium arsenide layers that increases their purity. A test element was implemented that allows non-destructive measurement of the mobility of charge carriers in the technological cycle of the formation of LSI structures. This allows us to realise the electrophysical diagnosis of the reliability of the LSI at the stage of crystal manufacturing

Measurements of electrophysical characteristics of semiconductor structures with the use of microwave photonic crystals

A method is proposed for the measurement of the electrophysical characteristics of semiconductor structures: the electrical conductivity of the n layer, which plays the role of substrate for a semiconductor structure, and the thickness and electrical conductivity of the strongly doped epitaxial n+ layer. The method is based on the use of a one-dimensional microwave photonic crystal with a violation of periodicity containing the semiconductor structure under investigation. The characteristics of epitaxial gallium-arsenide structures consisting of an epitaxial layer and the semi-insulating substrate measured by this method are presented.

Magnetoelectric effect in layered structures of amorphous ferromagnetic alloy and gallium arsenide

A paper devotes to theoretical and experimental studying the magnetoelectric interaction in layered structures of amorphous ferromagnetic alloy and single- crystal gallium arsenide.The authors investigated the magnetoelectric effect in the (100) plane of gallium arsenide in the electromechanical resonance range of 200–240kHz and obtained maximal ME voltage coefficient of 120V/A at bias field equaled 3.6kA/m for the direction parallel to the [011] axis. Also the magnetoelectric effect in the (110) and (111) planes is discussed. The results can be used for design of new electronic devices based on the magnetostrictive-semiconductor materials.

Determination of Band Structure of Gallium-Arsenide and Aluminium-Arsenide Using Density Functional Theory

This research paper is on Density Functional Theory (DFT) within Local Density Approximation. The calculation was performed using Fritz Haber Institute Ab-initio Molecular Simulations (FHIAIMS) code based on numerical atomic-centered orbital basis sets. The electronic band structure, total density of state (DOS) and band gap energy were calculated for Gallium-Arsenide and Aluminium-Arsenide in diamond structures. The result of minimum total energy and computational time obtained from the experimental lattice constant 5.63 A for both Gallium Arsenide and Aluminium Arsenide is -114,915.7903 eV and 64.989 s, respectively. The electronic band structure analysis shows that Aluminium-Arsenide is an indirect band gap semiconductor while Gallium-Arsenide is a direct band gap semiconductor. The energy gap results obtained for GaAs is 0.37 eV and AlAs is 1.42 eV. The band gap in GaAs observed is very small when compared to AlAs. This indicates that GaAs can exhibit high transport property of the electron in the semiconductor which makes it suitable for optoelectronics devices while the wider band gap of AlAs indicates their potentials can be used in high temperature and strong electric fields device applications. The results reveal a good agreement within reasonable acceptable errors when compared with the theoretical and experimental values obtained in the work of Federico and Yin wang [1] [2].

Implementation plasma chemical etching in submicron technology wsi structure

With the development of a range of sub–micron devices elements inthralnyh large schemes, a number of problems, which either did not exist in the development of technology of integrated circuits with minimum dimensions of elements, or they did not identify significant. Thus reducing the geometric dimensions topology structures LSI, accompanied by a decrease in the thickness of the functional layers of multilayer structures used to represent a theoretical requirements for selectivity and anisotropy etching layers introduced defects and radiation damage to the surface of the processed wafers of silicon or gallium arsenide structures of integrated circuits. To determine the optimal technological regimes digestion ranged basic operating parameters of the process – the composition and working gas pressure, bias voltage and holder, holder distance to the source plasma. This article reveals the same perspective and alternative use of submicron technology of plasma chemical etching.

First-principles study on the electronic structure and optical properties of GaAs nanowires

The electronic structure and optical properties of wurtzite gallium arsenide (GaAs) nanowires (NWs) are investigated within the first-principles plane-wave pseudo-potential method based on the density functional theory (DFT). The calculated results show that GaAs NWs are direct band gap semiconductor and demonstrate the achievement of p-type behavior. These NWs of the electronic behavior transitions from semiconductor to metal after hydrogen-passivated. The complex dielectric function, absorption coefficient and optical reflectivity are calculated and the peak position distributions of imaginary parts of the complex dielectric function have been explained. We may conclude GaAs NWs belongs to what crystal system through the dielectric tensors. Optical reflectivity is obtained and the peak position distributions of imaginary parts of the complex dielectric function have been explained, and their absorption spectra are sensitive to the large radius of GaAs NWs.