Surface-barrier Structures Research Articles

The influence of manufacturing modes on the electrical and energy parameters of graphene/p-CdTe Schottky diodes

The paper investigated the electrical properties of graphene/p-CdTe structures, which were distinguished by different durations of graphene films application on p-CdTe crystalline substrates: t1 = 5 min, t2 = 10 min and t3 = 15 min. The temperature of the substrates did not exceed TS = 523 K. The formation of graphene layers was confirmed by the study of Raman scattering spectra in the frequency range of 1000–3250 cm−1, in which the G and 2D bands with features characteristic of few-layer graphene appear. The established dependence of the electrical properties of the studied surface-barrier structures of graphene/p-CdTe on the duration of graphene films sputtering is well explained by the thermally stimulated change in the equilibrium characteristics of the base material and the formation of a near-surface layer with an increased concentration of acceptor-type defects (VCd), which is caused by the processes of the substrate components evaporation at its heating.

Photosensitivity of Nanostructured Schottky Barriers Based on GaP for Solar Energy Applications

This work investigates the surface-barrier photoelectric properties of Au-palladium-n-GaP structures. Research into the visible spectrum region, under the action of both linearly polarized and natural radiation, provides us with new information about the height of the barrier, the interface m-s section, and the GaP band structure. SBs based on GaP (p- and n-type) are helpful for researchers in developing advantageous structures for creating various photovoltaic devices—photodetectors for fiber-optic control of energy systems or possible structures for solar energy. Despite many years of research, issues concerning the band structure of semiconductors based on the phenomenon of photoelectroactive absorption in such surface-barrier structures’ m-s remain urgent in the creation of new high-performance devices. Such structures may also be interesting for creating solar energy systems. They create a thin insulating dielectric layer (usually an oxide layer) in solar cells on SBs between the m and the semiconductor substrate. The advantage of solar cells based on m dielectric semiconductor structures is the strong electric field near the surface of the semiconductor that usually has a direction favoring the collection of carriers created by short-wavelength light. Diffusion of impurities usually results in crystal defects in the active region. There are no such defects in the studied elements. This is also the difference between solar cells on m dielectric structures and elements with diffusion in p-n junctions. We studied the PS of Au-Pd-n-GaP nanostructures to determine the height of the potential barrier qφBo and obtained accurate data on the zone structure of the n-GaP. The PS of nanostructured Au-Pd-n-GaP structures was studied in the visible region of the spectrum. Essential information about the semiconductor’s potential barrier parameters and band structure was obtained. The intermediate Pd nanolayer between Au and GaP has specific effects on the Au-Pd-n-GaP nanostructure, which are of considerable practical and scientific significance for future needs.

Electric voltage redistribution effect in Schottky barrier structures based on Si under hydrostatic pressure

The paper presents the results of strain-effect studies in diode structures with Schottky barrier made on the basis of n-Si<P> and n-Si<P,Ni> with resistivities 102 - 105 Ohm·cm under all-round hydrostatic pressure. It is shown that as the resistivity of the base area of the structures increases, its rectifying properties worsens. It was found that the worse of the rectifying property of the surface barrier structures is not due to the presence of compensating impurities, but depends only on the resistance of the base area. In the Schottky barrier structures based on n - Si<P,Ni> with resistivities ~104 and 105 Ohm·cm the potential barrier is almost not formed. For the first time it was found that in structures with Schottky barrier under all-round hydrostatic pressure there is high strain sensitivity due to redistributions of electric voltage between the contact and the base area.

Model of the Kinetics of Photoconductivity Excitation in Surface-Barrier Structures

Model of the Kinetics of Photoconductivity Excitation in Surface-Barrier Structures

Device for Measurements of Ultraviolet’s Power Radiation

The paper presents a technique for developing a device for measurements of power of ultraviolet (UV) radiation. The paper provides a brief analysis of existing approaches in the design of UV dosimeters. The rationale for the design of the dosimeter using an UV photodiode is given. The choice of a photodiode based on cadmium sulfide is made on the basis of the technological equipment existing in Ukraine, the level of development of technological modes that allow, at low technology costs, to obtain photodiodes with parameters not inferior to expensive foreign analogues based on materials of the A3B5 group and silicon carbide. The problems that were solved when developing a photodiode based on CdS and the original solutions found by the authors of the development are shown. The primary transducer is a photodiode based on the surface-barrier structure of p-Cu1.8S/n-CdS with a photosensitive component based on cadmium sulfide CdS. At a wavelength of λ ~ 250 nm, the sensitivity of p-Cu1.8S/n-CdS sensors is two times higher than GaP-based Schottky diodes. The value of the output current depends on the power of the UV radiation and lies within 0.0001-0.2 mA. The advantages of the developed sensor are the simplicity and low cost of the production technology, the ability to produce films of a large area, the characteristics of expensive foreign industrial UV photodiodes. The stages of development of the amplifier circuit for the selected photodiode are given. To design the amplifier circuit, the existing GUVA-S12SD UV Sensor V2 amplifier circuit was analyzed, and a custom circuit was developed with the following advantages: unipolar power; smaller potential difference between input and output compared to analog; different voltages are measured. The developed circuit uses the simplest resistive voltage divider, which is two series resistors connected to a voltage source. The scheme denominations were calculated. The sequence of printed circuit board (PCB) execution in the Sprint-Layout software environment is described. An image of the developed circuit board is shown. An analog-to-digital converter K1108PV1A is selected for signal processing from the amplifier and its technical characteristics are given. The block diagram of the dosimeter of energy illumination is offered: a photodiode, an amplifier of an input signal, an analog-to-digital converter, a microcontroller. As a microprocessor to be connected to the ADC, an electronic stand based on a microcontroller will be used to debug programs using ATmega16A. The obtained circuit solutions for the construction of a UV dosimeter based on a CdS photodiode can be used to quickly create an industrial device that will be an integral part of the complexes for disinfecting the metro and other rooms from viral infections.

Fast-Neutron Detectors Based on Surface-Barrier GaAs Sensors with an Ultrahigh-Molecular-Weight Polyethylene Converter

Surface-barrier structures based on high-purity epitaxial GaAs layers with an ultrahigh-molecular-weight polyethylene converter were tested as fast-neutron detectors. The α-particle spectra and the response to fast neutrons were measured under exposure to a 241Am−Be source. The detectors demonstrated a high neutron-detection efficiency (1.22 × 10−3 counts/neutron) and an acceptable ratio of the signal to γ‑ray background (approximately 40). The possibility of using such detectors at temperatures as high as 120°C was shown.

Электрические и фотоэлектрические свойства поверхностно-барьерных структур МoN/n-Si

Электрические и фотоэлектрические свойства поверхностно-барьерных структур МoN/n-Si

Ultraviolet Sensors Based on ZnxCd1 – xS Solid Solutions

Effective semiconductor ultraviolet sensors on the basis of Zn0.6Cd0.4S and Zn0.7Cd0.3 solid solutions (SSs) are fabricated. The sensors include variband layers and a thin (∼10 nm) stable polycrystalline p-Cu1.8S film as a transparent component of the surface-barrier structure. The n-CdS layers are used as substrates for the epitaxial growing of SSs. The problems of obtaining low-resistive ZnxCd1−xS polycrystalline layers, providing an ohmic contact with them, and matching the lattice parameters in the SS and the substrate material are resolved by applying intermediate variband layers. On the basis of a heterostructure with glass filters, a selective sensor in the UV-A spectral interval is developed, as well as sensors sensitive to the pigmentation interval of solar radiation (the violet-blue section). Energy band diagrams of the multilayer structure are plotted. The results of Auger-spectroscopic researches and the researches of the main electrical and photovoltaic properties of sensors are reported.

Фотоприемники ИК-диапазона на основе изопериодических эпитаксиальных слоев халькогенидов свинца-олова

AbstractIR photodetectors have been made on Pb/δ-layer/ p -Pb_1 –_ x Sn_ x Te_1 –_ y Se_ y / p ^+-Pb_0.8Sn_0.2Te/Au and Au/δ-layer/ n -Pb_1 –_ x Sn_ x Te_1 –_ y Se_ y (BaF_2)/Pb surface-barrier structures prepared by liquid-phase epitaxy and thermal evaporation. At ~170 K, peak wavelength λ_ p ~ 7.9–8.2 μm, and cutoff wavelength λ_ c ~ 8.2–8.5 μm, the former surface-barrier structure has product R _0 A (where R _0 is the zero-bias differential resistance and A is the active surface area) = 0.31–0.97 Ω cm^2, peak quantum efficiency η_λ = 0.32–0.48, and specific detectability $$D_{\lambda }^{*}$$ = (0.72–1.83) × 10^10 cm Hz^1/2 W^–1. For photodiodes made on the latter surface-barrier structure, these parameters measured at ~80 K are R _0 A = 1.71–2.72 Ω cm^2, η_λ = 0.34–0.49, and $$D_{\lambda }^{*}$$ = (3.02–4.51) × 10^10 cm Hz^1/2 W^–1 at λ_ p ~ 8.6–12.3 μm and λ_ c ~ 9.2–12.9 μm.

HETEROLAYERS OF ANISOTROPIC α-ZnSe FOR PHOTOSENSORS

The optical, luminescence and electrical properties of α-ZnSe heterolayers obtained by the method of isovalent replacement are investigated. The high quantum yield of luminescence η = 10-12% in the short-wave region is established. The dominant role of excitons annihilation and interband transitions of free charge carriers is revealed. The surface-barrier structures of Ni-α-ZnSe, whose spectral region of photosensitivity is ħω = 2.70-3.75 eV, was made. The hexagonal modification of the structure of the obtained heterolayers causes their polarization properties of reflection and photosensitivity.

Influence of Isotropic Pressure on the Current–Voltage Characteristics of Surface-Barrier Diodes Sb–p-Si〈Mn〉–Au

The influence of hydrostatic pressure on the current–voltage characteristics of surface-barrier diode structures of the Sb–p-Si〈Mn〉–Au type are investigated. The potential-barrier height and the baric coefficient of its variation are found to be eϕδ = 0.75 eV and δ =–1.54 × 10–11 eV/Pa, respectively.

Fabrication and photosensitivity of structures based on CdS:Au nano-particles nanocomposite

In order to improve the light trapping in CdS/CdTe thin-film solar cells, the metallic nano-particles embedding can increase the photoabsorption as a result of the enhanced electric field and forward-scattering upon excitation of the surface plasmon resonance (SPR). This paper investigates how chemically deposited gold nano-particles array affects the CdS film optical properties. The surface morphology, and absorption of the CdS thin films decorated on top or inside with Au nano-particles array were studied in subsequent stages of the technological process. The SPR effect, an enhanced light absorption and photosensitivity in the visible range of spectrum for CdS:Au nano-particles nanocomposite films was shown. The spectral responsivity region for the ITO/CdS:Au NPs/Ag surface barrier structures was found to be extended to the long-wavelengths. Using Finite Element Method simulations, the plasmon resonance wavelength for fabricated Au nano-particles geometries was calculated and compared with experimental data. The results of this paper will contribute to the optimization of plasmonic CdS/CdTe solar cell and will pave the way for the development of highly efficient solar cell devices.

Влияние изотропного давления на вольт-амперную характеристику поверхностно-барьерных диодов Sb-p-Si&amp;lt;Mn&amp;gt;-Au

AbstractThe influence of hydrostatic pressure on the current–voltage characteristics of surface-barrier diode structures of the Sb– p -Si〈Mn〉–Au type are investigated. The potential-barrier height and the baric coefficient of its variation are found to be e ϕ_δ = 0.75 eV and δ =–1.54 × 10^–11 eV/Pa, respectively.

Electrical and Photoelectrical Properties of Surface Barrier Structures MoOx/n-Si

Electrical and Photoelectrical Properties of Surface Barrier Structures MoOx/n-Si

The influence of surface barriers on the photoemission characteristics of AlGaN photocathodes

In order to research the photoemission characteristics of AlGaN photocathodes with different surface barrier structures, AlGaN photocathodes with varying Al composition were grown by MOCVD. The atomic composition of the photocathode surface was measured by Ar+ ion sputtering and XPS. We find that the C atoms only exist at the surface, but O atoms are present up to 6nm from its surface. The photocathodes were cleaned and activated with different processing methods, and the result show that the quantum efficiency value of Cs/O activated AlGaN photocathodes were about 42% higher than that of Cs-only activated AlGaN photocathode. Through thermal cleaning at 850°C and Cs/O activation, the maximum quantum efficiency of the AlGaN photocathode was 49.39% at 240nm. Through simulation of the electronic energy distribution, we determined that the surface barrier I structure formed by [AlGaN: Mg-Cs] dipoles at the photocathode surface was mainly affecting the surface electrons escapes probability and determining the photocathode quantum efficiency. The surface barrier II structure formed by [Cs-O] dipoles at the photocathode surface determined the photocathode performance, and also affected the electronic energy distribution concentration.

Characterization and simulation of fast neutron detectors based on surface-barrier VPE GaAs structures with polyethylene converter

Fast neutron detectors with an active area of 80 mm2 based on surface-barrier VPE GaAs structures were fabricated and tested. Polyethylene with density of 0.90 g/cm3 was used as a converter layer. The recoil-proton surface-barrier sensor was fabricated on high purity VPE GaAs epilayers with a thickness of 50 μm. The neutron detection efficiency measured with a 241Am-Be source was 1.30 · 10−3 puls./neutr. for the PE converter thickness of 670 μm. The signal-to-gamma-background ratio was at the level of 50. Simulation of the detector characteristics with Geant4 toolkit has showed good correlation with the experimental data and allowed to estimate the maximal theoretical detection efficiency of the detector which is determined by the PE converter and equals to 1.37 · 10−3 puls./neutr. The difference between the measured and simulated values of the detection efficiency is due to the fact that the events with energies below 0.5 MeV were not taken into account during the measurements.

CONTROL OF CURRENT TRANSPORT IN SCHOTTKY DIODE USING THE QUANTUM DOTS

SummaryPurpose. In the framework of the drift-deformation-diffusion approximation considering the self-consistent boundary conditions, investigate the current-voltage characteristic (CVC) of surface-barrier structure of type Schottky with built layer of quantum dots and establish the criteria for the technological parameters of surface-barrier structure of type Schottky with built layer of quantum dots at which current-voltage characteristic has S-shaped character. Research methods. Method of self-consistent boundary conditions. Research results. As seen from the numerical calculations, the current-voltage characteristic (CVC) of low barrier (åV5.0≤Δ) Schottky diode with built layer of quantum dots in the space charge region is S-shaped nature. With increasing barrier height Δ to 0.9 eV the area of negative differential resistance on CVC is disappears, and in the interval of voltages 0.5V - 1V has exponential character. Variation of thickness i- layer (0d0RLL−=) of  toA150 leads to changing the character of CVC, i.e. the instability current of S-type is disappears. In this work the results of numerical calculations of CVC for the direct direction of displacement at two values of temperature (T = 77 K, 300K) is given. As seen from the graphs CVC in the range of the voltages Â52.0VÂ24.0&lt;&lt; the value of the current density of voltage at T=77 K is smaller than at T=300K.Conclusions1. It is established that current-voltage characteristic (CVC) of low barrier (åÂ5.0≤Δ) Schottky diode with built layer of quantum dots in the space charge region is S-shaped nature, when the layer of quantum dots is located at distances from the boundary of the contact metal-semiconductor of the order of (10-30)0a, where 0a is the period lattice of the semiconductor.2. It is shown that both the increasing barrier height Δof 0.5 eV to 0.9eV, and the distance from the metal to layer of QD (dL) of A50 to A150, the area of negative differential resistance on CVC is disappears.3. At high potential barrier (0.9eV) the contact effects is dominate and the site of the exponential dependence on voltage (0.5V-1V) on CVC is present, and the lower potential barrier the dependence of current on voltage is approximates to a quadratic (V&gt; 0.6B).

Surface-barrier photoconverters with graded-gap layers in the space-charge region

A novel possibility of controlling the parameters of p-Cu1.8S-n-II-VI surface-barrier structures by embedding a thin graded-gap layer into a photoconverter space-charge region (SCR) is implemented. The feature of quasi-electric fields built in the SCR, i.e., the fact that an increase in the drift field for minority carriers can be accompanied by a decrease in the potential barrier for majority carriers, is considered. The proper choice of the parameters of the Cd x Zn1 − x S graded-gap layer embedded in the Cu1.8S-ZnS structure SCR made it possible to double the quantum efficiency in the ultraviolet spectral region. For Cu1.8S-CdS photoconverters with a (CdS) x (ZnSe)1 − x intermediate layer, dark diode currents are decreased by three orders of magnitude while retaining a high quantum efficiency.

Thin-film solar converters based on the p-Cu1.8S/n-CdTe surface-barrier structure

Thin-film solar converters based on the p-Cu1.8S/n-CdTe surface-barrier structure

Effects of surface barrier layer in AlGaAs/GaAs solar cells

In this paper, we report the effects of surface barrier layers on the characteristics of AlGaAs/GaAs solar cells. The external quantum efficiency (EQE) spectra for AlGaAs barrier samples with different barrier layer AlAs fractions and thickness of the surface barrier layer were measured to increase the solar cell efficiency. The results show that the surface barrier layer is effective to block diffusing photoexcited electrons to the surface while the thicker barrier layer absorbs higher energy photons to generate carriers which recombine at the surface. The optimal surface barrier structure is a 50nm thick Al0.7Ga0.3As.