High-resistivity Layer Research Articles

Nitrogen-doped β-Ga2O3 vertical transistors with a threshold voltage of ≥1.3 V and a channel mobility of 100 cm2 V−1 s−1

We demonstrate high-performance normally-off multi-fin β-Ga2O3 vertical transistors with a wide fin width from 1.0 to 2.0 μm by using a nitrogen-doped β-Ga2O3 high-resistive layer grown by halide vapor phase epitaxy. Normally-off operation was achieved with a threshold voltage of ≥1.3 V, a specific on-resistance of 2.9 mΩ·cm2 and a current density of 760 A cm−2 at a gate voltage of +10 V. The estimated MOS channel field effect mobility was ∼100 cm2 V−1 s−1. These findings offer important insights on the development of Ga2O3 MOSFETs and show the great promise of Ga2O3 vertical power devices.

Application of geophysical techniques for shallow groundwater investigation using 1D-lateral constrained and 2D inversions in Ras Gara area, southwestern Sinai, Egypt

There is an urgent need for greater water resources to support sustainable development in Ras Gara area of southwestern Sinai. Determining the water-bearing zones of the shallow Quaternary aquifer of the Araba Formation in the study region is therefore the main objective of the research. This will be done by using a variety of geophysical techniques, such as DC resistivity sounding and shallow seismic refraction surveys. Using the Schlumberger array (max. AB = 1200 m), the DC data were gathered at 27 VES locations along five primary profiles. At the same locations, 27 spreads totaling 115 m in length of seismic data were also performed. One-dimensional laterally constrained (1D-LCI) inversion is only applied to the DC data in order to generate a best-fit model, whereas 2D inversion is applied to other datasets. The area is divided up into five geo-electrical layers based on the results of 1D-LCI inversion of DC data, and the aquifer is classified into fresh (third layer) and saline bearing-zones (fourth layer). The resistivity values of the fresh-zone range from 8.7 to 26.7 Ω.m, with only low values (5–7.5 Ω.m) found at some VES sites, while the resistivity values of the saline-zone range between 0.9 and 3 Ω.m, except for (14.4 Ω.m) at VES-04. At depths of (2.4–15.6 m) and (8.7–28.5 m) for the fresh and saline zones, respectively. In this region, the shallow low resistive (about 10–100 Ω.m) and intermediate high conductive (< 10 Ω.m) layers of the 2D-DC inverted model represent the fresh and saline zones of the aquifer, respectively. The basement rocks were represented by a deep, extremely high resistive layer that can reach 40,000 Ω.m. Three subsurface layers are identified from the results of the 2D inversion of seismic data (VP1 = 400–1100 m.s−1, VP2 = 1200–1900 m.s−1 and VP3 = 2400–5400 m.s−1). The saturated zone of this aquifer is represented by the second layer (depth, 3.7–20.5 m). The basement rocks are also reflected in the last layer of high velocity. The inversion results and the previously available hydro-geological map data show a good degree of concordance. In the eastern portion of the study area, additional water wells could be drilled for additional water resources.

Hydrodynamic simulation of hypervelocity generation by multidimensional graded impactors: Planarity enhancement study

Hypervelocity impact in the universe can be generated by a three-stage gas gun. Achieving the desirable planarity of the flyer enlarges the experimentally effective area of the flyer under the hypervelocity condition. The multidimensional graded density impactor (MDGDI) enhances the planarity of the flyer. In this investigation, a one-dimensional Lagrange elastoplastic hydrodynamic method and a Euler grid finite difference method were used to examine the relationship between the structure of graded density impactors (GDIs) and the planarity of flyers. MDGDIs lead to a deviation of the stress wave produced by the one-dimensional graded density impactor (1DGDI), which offsets the stress disturbance effect, changes the velocity at each particle, and enhances the planarity of flyers. The proportion of flat areas of the flyer increases from 52.70% to 95.71% by adopting MDGDIs. The proportion of flat areas is linear with the wave impedance of the high-impedance layer for 1DGDIs and the wave impedance near the barrel of the high-impedance layer for MDGDIs. This investigation guides the design of GDIs and expands the application of gas gun technology in the field of hypervelocity impact.

Electrical resistivity structure across the Late Cenozoic Abaga-Dalinor volcanic field, eastern China, from 3-D magnetotelluric imaging and its tectonic implications

The Abaga-Dalinor volcanic field (ADVF) in Inner Mongolia, China, located to the west of the North-South Gravity Lineament (NSGL), is the largest and less known area of Late Cenozoic intraplate volcanism in Northeast China. Knowledge of the subsurface structure beneath the ADVF will improve our understanding of its evolution process and formation mechanisms. New broadband magnetotelluric (MT) data were collected along a profile of about 300 km that crosses the major basaltic areas exposed at the surface in the ADVF and a series of east-north-east (ENE) trending faults. The electrical resistivity structure of the crust and uppermost mantle across the ADVF was generated by 3-D inversion of full impedance tensor and tipper data. This model reveals a thick high-resistivity layer (>1000 Ωm) in the upper crust that may represent the Precambrian basement and Late Paleozoic-Mesozoic granitic plutons. In contrast, high conductivity anomalies dominate the middle-lower crust. The northward-dipping high-conductivity feature at depths of 20–40 km below sea level under the Chagan Obo fault is suggested to be the involvement of the Early Paleozoic subducted oceanic crust. A remarkably high-conductivity zone (1–20 Ωm) exists in the middle-lower crust beneath the Abaga and Dalinor volcanic areas. It is explained to be a saline fluid zone of ∼0.45%–0.48% that exsolved from the partial melts as magma ascent rapidly. The impermeable upper crust traps these fluids in the middle-lower crust. A moderately high-conductivity anomaly in the uppermost mantle below near the Solonker Suture Zone (SSZ) is attributed to a minimum partial melt of ∼3–4% associated with the localized asthenospheric upwelling, which feeds the Abaga and Dalinor volcanos as a common magma source. Integrating our resistivity model with previous geophysical and geochemical studies, we suggest that intraplate volcanism in the ADVF is mainly controlled by the pre-existing tectonic weak zones. The lithosphere within the SSZ is susceptible to thermal perturbation from the upwelling mantle, providing the preconditions for melt generation. A set of ENE trending faults and an inferred NW-SE trending fault jointly dominated the vertical transport of magma and lateral extension along the faults, which may have influenced the spatial distribution of basalts and volcanic cones at the surface in the ADVF. In addition, we tend to suggest that Late Cenozoic intraplate volcanism in the ADVF could be the result of decompressing melting within the localized small-scale asthenospheric upwelling induced by the edge-driven convection near the NSGL, which is indirectly related to the westward subduction and retreat of the (Paleo-)Pacific plate during the Late Mesozoic to Cenozoic.

Boundary detection capability and influencing factors of electromagnetic resistivity while using drilling tools in a horizontal well

With the increase in the scale of mining in horizontal and highly deviated wells, electromagnetic boundary detection while drilling plays an important role in boundary detection. This paper examines three types of antenna structures commonly used in electromagnetic boundary detection and measurement methods and also performs a numerical simulation of the edge detection capability of the three structures in horizontal wells. The simulation experiment analyzes the influence of formation resistivity contrast, frequency, spacing, and other factors on the capability of edge detection and provides data that supports the design of instrument antenna parameters. The numerical simulation shows that the tilted and orthogonal receiving antennas demonstrate improved performance both in detecting the interface when approaching from high-resistance layers and low-resistance layers. In addition, the capability of boundary detection can be improved by decreasing the frequency and increasing the spacing between the transmitter and receiver.

Study of the anisotropy of frozen rocks at the Khanovei test site (Komi Republic) based on the data of controlled source radio-magnetotelluric soundings and electrical resistivity tomography

The results of a joint inversion of the data of controlled source radio-magnetotelluric soundings (CSRMT) and electrical resistivity tomography (ERT), obtained at the Khanovei permafrost test site near Vorkuta, are presented. The geological section in the work area is composed of Quaternary fluvio-glacial, lacustrine-glacial and alluvial deposits up to 60 m thick, overlying a sequence of sandstones, siltstones and mudstones of Permian age. The CSRMT survey was carried out using a grounded electrical line 480 m long as a source in the frequency range 1-1000 kHz. The results of various inversion options were compared: 1) isotropic one-dimensional (1D) inversion of CSRMT data; 2) isotropic separate two-dimensional (2D) inversion of CSRMT and ERT data; 3) joint anisotropic 1D inversion of CSRMT and ERT data. Based on the results of a joint anisotropic inversion of CSRMT data in the far and intermediate zones of the source and ERT data, a vertical anisotropy associated with horizontal layering of frozen Quaternary clay deposits in the depth range from 2 to 15-20 m was revealed and its parameters (horizontal and vertical resistivity and anisotropy coefficient) were determined. On the geoelectric section obtained from the ERT data, the thickness of the anisotropic layer of frozen clayey deposits is significantly overestimated. The middle part of the section, in the depth range from 15-20 to 60-70 m, is characterized by relatively low resistivity values (tens of ohmmeters). This is consistent with the results of previous studies, which established that the upper part of the Permian sediments is in a thawed state and is fractured and water-saturated. A high-resistivity layer (hundreds of ohmmeters) was revealed at the base of the geoelecric section according to CSRMT data. A significant increase in the resistivity of Permian rocks with depth is confirmed by the data of vertical electrical soundings previously performed in the Khanovey area.

Design of Tunable Liquid Crystal Lenses with a Parabolic Phase Profile

An electrode pattern design generating a parabolic voltage distribution, in combination with usage of the linear response range of the liquid crystal (LC) material, has been recently proposed to obtain nearly ideal phase profiles for LC lenses. This technique features low driving voltages, simple structure, compact design, and the absence of high-resistivity (HR) layers. In this work, the universal design principle is discussed in detail, which is applicable not only to LC lens design, but also to other LC devices with any phase profile. Several electrode patterns are presented to form a parabolic voltage distribution. An equivalent electric circuit of the LC lens based on the design principle is developed, and the simulation results are given. In the experiments, an LC lens using the feasible parameters is prepared, and its high-quality performance is demonstrated.

Synthesis and electrophysical properties of CdS/ZnTe heterojunctions

In this paper results of studying CdS/ZnTe heterostructures synthesized by the quasi-closed space sublimation method on glass substrates coated with an ITO layer are described. The electrical and photoelectric properties of the structures are studied using current–voltage and capacitance–voltage characteristics in a temperature range of 30–100 °C. Analysis of the experimental data shows that the main specific feature of CdS/ZnTe structures is the formation of a high-resistance transition layer, which affects the separation of carriers at the barrier contact. The current carrier concentration in the space charge region, which is determined from the capacitance–voltage characteristics, is 1 x 1015 cm-3; this fact suggests that one of the contacting materials—ZnTe—exhibits a high resistivity. Measurements of current–voltage characteristics in the solar cell mode give the following photoelectric parameters: open circuit voltage (UOC = 0.53 V, JSC = 27–30 A/cm2, and FF = 0.25.

Ga2O3/GaN-based solar-blind phototransistors fabricated using a thermal oxidation process performed on the GaN p-n junction layers

In this article, β-Ga2O3/GaN-based solar-blind phototransistors are fabricated using a thermal oxidation process performed on the p-GaN layer of a p-GaN/n-GaN junction to form the β-Ga2O3/p-GaN/n-GaN heterostructure. The thermal-oxidized β-Ga2O3 films exhibit a (2̅01)-orientated crystal phase and high-resistivity property. The high-resistivity β-Ga2O3 layer can be converted into an n-type β-Ga2O3 layer through Si ion implantation and a subsequent thermal annealing process. The typical electron concentration and mobility of the Si-implanted β-Ga2O3 are as high as 3.2 × 1020 cm−3 and 177 cm2v−1s−1, respectively. The n-type β-Ga2O3 and unimplanted β-Ga2O3 layers serve as the collector associating with the p-GaN and n-GaN layers, which function as the base and emitter, respectively, to construct the heterojunction phototransistors (HPTs). The HPTs exhibit a distinct cut-off wavelength at around 260 nm, indicating that the photocurrents result from the β-Ga2O3 layers rather than the p-GaN and n-GaN layers. The HPTs also show a significant bias-dependent responsivity in the deep UV (λ < 260 nm) region. This increased responsivity can be attributed to band discontinuity, resulting in the accumulation of photogenerated carriers at the β-Ga2O3/p-GaN interface. The preliminary results suggest that the β-Ga2O3/GaN-based HPTs can be achieved through the thermal oxidation of a p-GaN/n-GaN epitaxial structure.

ELECTRICAL AND PHOTOELECTRIC PROPERTIES OF P-CDS/P-CDTE/ZNTE/ZNCDS HETEROJUNCTIONS

Studies show that during thermal processing, major changes occur in p-CdS/p-CdTe/ZnTe/ZnCdS heterojunctions. The nature of the change in electrical and photoelectric properties of heterojunctions depending on thermal processing conditions shows that the volume charge layer expands due to the presence of acceptor levels near the surface of the Zn1-xCdxS layer (Fig. 1). Therefore, the capacity of p-n heterojunctions decreases. The increase in photoresponse across all spectra indicates that the compensation of donor-type natural defects with acceptor levels results in the formation of a high-resistivity layer in the near-surface layer and increases the rectification factor. Light absorption is more effective due to the high resistivity layer, which means that the utility of the absorbed beam and the accumulation of carriers with p-n heterojunctions are increased.

Low-voltage driving high-resistance liquid crystal micro-lens with electrically tunable depth of field for the light field imaging system

Light field imaging (LFI) based on Liquid crystal microlens array (LC MLAs) are emerging as a significant area for 3D imaging technology in the field of upcoming Internet of things and artificial intelligence era. However, in scenes of LFI through conventional MLAs, such as biological imaging and medicine imaging, the quality of imaging reconstruction will be severely reduced due to the limited depth of field. Here, we are proposed a low-voltage driving LC MLAs with electrically tunable depth of field (DOF) for the LFI system. An aluminum-doped zinc oxide (AZO) film was deposited on the top of the hole-patterned driven-electrode arrays and used as a high resistance (Hi-R) layer, a uniform gradient electric field was obtained across the sandwiched LC cell. Experimental results confirm that the proposed LC MLAs possess high-quality interference rings and tunable focal length at a lower working voltage. In addition, the focal lengths are tunable from 3.93 to 2.62 mm and the DOF are adjustable from 15.60 to 1.23 mm. The experiments demonstrated that the LFI system based on the proposed structure can clearly capture 3D information of the insets with enlarged depths by changing the working voltage and driving frequency, which indicates that the tunable DOF LC MLAs have a potential application prospects for the biological and medical imaging.

Fabry-Perot resonance-suppressed double-layer metal mesh window for electromagnetic interference shielding.

Traditional electromagnetic interference shielding windows that can simultaneously reflect microwaves and transmit visible light are usually fabricated by depositing one metal mesh layer on the surface of the window. However, such a structure always suffers from strong Fabry-Perot resonance (FPR), which leads to the decline of shielding effectiveness (SE). Here, we analyze the mechanism of FPR from a perspective of the equivalent circuit model and further report a facile approach to minimize the FPR by depositing another high-resistance mesh layer on the back side of the shielding window, which can greatly reduce reflected waves, ensuring that interference cannot be formed. Simulation results prove that FPR can be effectively eliminated by the proposed method, and experiments further show that for a shielding window made with Schott B270 glass plate, the SE can be enhanced by 6.3 dB (76.6% energy attenuation) at declining points, while transmittance is only reduced by 1.6%.

Comparison of different sensor thicknesses and substrate materials for the monolithic small collection-electrode technology demonstrator CLICTD

Small collection-electrode monolithic CMOS sensors profit from a high signal-to-noise ratio and a small power consumption, but have a limited active sensor volume due to the fabrication process based on thin high-resistivity epitaxial layers. In this paper, the active sensor depth is investigated in the monolithic small collection-electrode technology demonstrator CLICTD. Charged particle beams are used to study the charge-collection properties and the performance of devices with different thicknesses both for perpendicular and inclined particle incidence. In CMOS sensors with a high-resistivity Czochralski substrate, the depth of the sensitive volume is found to increase by a factor two in comparison with standard epitaxial material and leads to significant improvements in the hit-detection efficiency and the spatial and time resolution.

Improvement of current withstand capacity of high gradient ZnO varistors

The effects of the dispersant and the inorganic high resistance coating on the microstructure and the electrical properties of the ZnO varistors, especially on the current withstand capacity, were studied. The results showed that under the premise of adequate slurry dispersion, when the dispersant content was the minimum, the porosity of the varistor was the minimum, and the current withstand capacity was up to 24 A/cm2 in 2 ms square waveform impulse test. By coating a high resistance layer with high proportion of spinel forming elements, the content of spinel near the side of the varistor ceramic was increased, thus increasing the resistivity and alleviating the current impact near the edge. The current withstand capacity of 2 ms square waveform impulse was upgraded to 32 A/cm2.

Development of the micro-RWELL discs for the CMD-3 detector

The CMD-3 is general purpose detector at the VEPP-2000 electron–positron collider at Budker Institute of Nuclear Physics. CMD-3 is intended to measure parameters of light vector mesons and main hadronic cross sections with accuracy better than 1% and study dynamics of multihadron production. In order to increase geometrical acceptance for charged particles and to improve precision of track polar angle measurements the end-cap discs based on micro-resistive-WELL (μ-RWELL) structures are proposed for the upgrade of the CMD-3 tracking system. Two μ-RWELL discs 50 cm in diameter were assembled and tested. The discs have two-layer readout structure with the top layer of quarter-rings with 2 mm pitch in radius and the bottom layer of sectors with average angular pitch of about 0.3 degrees. The quarter-rings occupy only 50% of the disc surface due to gaps between them, thus, allowing the signal to be induced on the bottom layer. The kapton foil with copper layer on top and high-resistivity DLC layer at the bottom, pierced with 80 micron diameter holes located at 140 micron from each other, is glued on top of the readout structure. With the first disc the manufacturer (CERN advanced PCB Workshop) could not reach proper insulation between the copper layer and the DLC and the copper was etched out leaving the disc with thin Ni–Cr adhesion layer on top. The second disc has copper layer on top of the μ-RWELL structure. The readout structure of the discs is connected to front-end electronics based on VMM3a ASICS. The results of study of the main parameters of the detectors with front-end electronics are reported in the paper.

Lowering the sintering temperature of Li&lt;sub&gt;7&lt;/sub&gt;La&lt;sub&gt;3&lt;/sub&gt;Zr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt; electrolyte for co-fired all-solid-state batteries via partial Bi substitution and precise control of compositional deviation

Li7La3Zr2O12 (LLZ) has great potential as a solid electrolyte for co-fired all-solid-state Li-ion secondary batteries. However, to realise a solid-state battery using LLZ, the sintering temperature of LLZ should be reduced to one that can suppress the formation of a high-resistance reaction layer at the interface between LLZ and the electrode. In this study, we demonstrate an effective method for reducing the sintering temperature of Li6La3ZrTaO12 by combining partial Bi-substitution for Ta and precise control of the compositional deviation. The intentional tuning of the La deficiency in Li6La3ZrTa0.8Bi0.2O12 (LLZTB0.2) promoted the formation of a liquid phase based on Li2O–Bi2O3 at the grain boundary, resulting in its densification at 775 °C. Furthermore, we fabricated a co-fired all-solid-state half-cell based on an LLZTB0.2 electrolyte attached to a LiCoO2 + LLZTB0.2 composite electrode and a half-cell operated at 60 °C. From these results, it was found that the proposed concept is effective in reducing the sintering temperature of LLZ and is applicable for co-firing an all-solid-state battery.

Prospective Evaluation of Geothermal Resources in the Shangqiu Uplift of the Southern North China Basin with Magnetotelluric Detection

The magnetotelluric sounding (MT) method is used to detect and study the deep stratigraphic structure and hidden faults in the Shangqiu Uplift. A total of 4 MT profiles are arranged, and 97 stations are collected. The nonlinear conjugate gradient (NLCG) two-dimensional inversion method is used to jointly invert data from both the TE and TM modes after a dimensionality analysis and impedance tensor decomposition; reliable two-dimensional resistivity models are produced since the data quality is excellent. Three-dimensional inversion is carried out to full impedance tensor as well to produce a three-dimensional resistivity model of the study area, which shows good consistency with the two-dimensional models. The results show that the electrical structure of the Shangqiu Uplift has typical layered characteristics, which can be divided into three layers from top to bottom, namely low-, medium-to-high-, and high-resistivity layers. According to the resistivity models and in combination with the gravity, aeromagnetic, seismic, and regional geological data of the study area, a geological map of the basement rock of the Shangqiu Uplift is produced. Two prospective geothermal anomaly areas are proposed according to the distribution of the high-resistivity anomaly formed by the basement uplift, which has a good corresponding relationship with the high-value area of the regional geothermal field. A geothermal exploration well (SR-1) is constructed in one of the inferred prospective geothermal anomaly areas. The well is 1702 m deep, with a water output of 1500 m3/day and a wellhead water temperature of 51.5 °C. This is the geothermal well with the largest water yield in the Shangqiu area at present, which provides a new basis for future geothermal exploration, development, and utilization.

EFFECT OF RAPID THERMAL ANNEALING TEMPERATURE ON THE ELECTROPHYSICAL PROPERTIES OF THE OHMIC CONTACT OF Ti/Al /Ni METALLIZATION TO THE GaN/AlGaN HETEROSTRUCTURE

Effect of rapid thermal annealing temperature on the electrophysical properties of the ohmic contact of Ti/Al/Ni metallization with layer thicknesses of 20/120/40 nm to the GaN/AlGaN heterostructure with a two-dimensional electron gas on a sapphire substrate has been discovered by transmission line measurement and secondary ion mass spectroscopy methods. Rapid thermal annealing of the samples was carried out in a nitrogen atmosphere at the temperature ranging from 850 to 900 °C for 60 s. It has been discovered that a high-resistance heterostructure layer with a thickness of about 25 nm is located on the initial samples between metallization and the two-dimensional electron gas, which prevents the formation of ohmic contact. After rapid thermal annealing at the temperature of less than 862,5 °C, the metallization components interact with each other and with the heterostructure, which leads to the decrease in the thickness of the high-resistance heterostructure layer to 15–20 nm and to the nonlinearity of the I – V characteristic. At rapid thermal annealing temperatures in the range from 862,5 to 875 °C, the thickness of the high-resistance heterostructure layer decreases to several nanometers due to the interaction of Ti/Al/Ni metallization components with the heterostructure, which promotes the tunneling effect of charge carriers and formation of a high-quality ohmic contact with a resistivity of about 1⸱10 –4 Ohm∙cm 2 . With an increase of the rapid thermal annealing temperature over 875 °C, the interaction of the metallization and heterostructure components occurs throughout the entire depth, the two-dimensional electron gas degrades, and the I – V characteristic of the contact becomes nonlinear. The results obtained can be used in the technology for creating GaN-based products with a two-dimensional electron gas.

Born approximation imaging technique for electrical source multi-component TEM

Abstract In this study, to obtain higher-resolution geoinformation in the electrical source transient electromagnetic method (TEM) interpretation, the pseudo-seismic Born approximation imaging method is applied to the vertical magnetic induction intensity ${B_z}$ and the horizontal electric field ${E_y}$, which is paralleled to the source. First, the differences between the two components are compared, and the results reveal that different components can reflect varied geological information. ${E_y}$ has a stronger signal and is more sensitive to the high-resistivity layer at a long offset, whereas ${B_z}$ has a greater relative difference in the low-resistivity layer at a short offset. The TEM field is then transformed into the pseudo-wavefield using the wavefield transformation method and the Born approximation pseudo-seismic imaging method is adopted to locate the electrical interface. After calculating the 3D model, the results indicate that the multi-component Born approximate imaging can intuitively and effectively locate the depth of the geological interface. Furthermore, the imaging results of a coal mine located in Gansu Province, China, proves that the proposed method can pinpoint the buried location of the coal goaf as well as the stratum trend. In general, the multi-component pseudo-seismic imaging technique plays a significant role in interpreting the electrical source TEM data.

Influence of sputtered gallium oxide as buffer or high-resistive layer on performance of Cu(In,Ga)Se2-based solar cells

Influence of sputtered gallium oxide as buffer or high-resistive layer on performance of Cu(In,Ga)Se2-based solar cells