Base Collector Research Articles

Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0mg/L, except DXM (0.8mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120min. After 15min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Characteristics and Degradation Mechanisms under High Reverse Base-Collector Bias Stress in InGaAs/InP Double HBTs.

In this paper, the reliability of InP/InGaAs DHBTs under high reverse base-collector bias stress is analyzed by experiments and simulation. The DC characteristics and S parameters of the devices under different stress times were measured, and the key parameters with high field stress were also extracted to fully understand and analyze the high-field degradation mechanism of devices. The measurements indicate that the high-field stress leads to an increase in base current, an increase in base-collector (B-C) and base-emitter (B-E) junction leakage current, and a decrease in current gain, and different degrees of degradation of key parameters over stress time. The analysis reveals that the degradation caused by reverse high-field stress mainly occurs in the B-C junction, access resistance degradation, and passivation layer. The physical origins of these failure mechanisms have been studied based on TCAD simulation, and a physical model is proposed to explain the experimental results.

Sensible heat thermal energy storage performance of mono and blended nanofluids in a free convective-radiation inclined system

The photothermal conversion performance (PCP) of a nanofluid-based solar energy system is investigated numerically and experimentally. The impacts of particle size, volume concentration, nanoparticle type, base fluid type and collector inclination angle on the PCP are investigated. It is observed that using nanoparticles improves the ability to absorb solar energy. Temperature gain is 2.2, 3.2, 3.8, 4.2, and 9 times better than pure water for water-based Al, Al2O3, Au, Cu, and Graphite mono nanofluids, respectively. Interestingly, blended nanofluids containing the same nanoparticles significantly argument the optical properties, with useful heat enhancement ranging from 62.8 (mono) to 194 kJ/kg (hybrid). However, the collector's inclination angle, which ranges from 0 to 60°, has a negative impact on the PCP by reducing the solar radiation absorption of the nanofluids due to a decrease in the radiation penetrating the collector. Furthermore, as nanoparticle size increases, so does the thermal performance of the nanofluid. An experimental investigation is carried out for pure water and nanofluid at various wind speeds and solar irradiation levels ranging from 1 to 4 m/s and 200–1000 W/m2, respectively, to validate the numerical results.

“Africanness” in the Oeuvre of the Ceramist Esias Bosch (1923–2010)

It has been claimed that the oeuvre of stoneware studio pottery by Esias Bosch (1923–2010), the country’s pioneering figure of that discipline, conveys an Africanness in the look and feel of the works. Such assumed attributes relating to Africa are contestable when considering which and whose values and meanings are assigned to Africa, Africanity, and Africanness. Newly found archival material elaborates on the first-hand engagement by Bosch with an indigenous cultural tradition of pottery in Nigeria and the revisioning of some of its forms by Michael Cardew (1901–1983) at the Abuja Pottery Training Centre. Although the new archival material sheds light on Bosch’s encounter with one of Africa’s indigenous cultural traditions of pottery, it does not support the claims that his stoneware oeuvre can be characterised as being reflective of Africa. The context of such characterisation must be considered against the backdrop of the evolution of South African studio pottery, with practitioners seeking to develop signature styles that would appeal to the consumer and collector base, hitherto prejudiced towards mass-produced ceramics with Western features. This article addresses issues of Western-orientated perspectives of “tradition”, cultural referencing, and identity.

Simulation analyses of carrier dynamics in npn-type GaN-heterojunction bipolar transistors with different hole-concentration p-base layers

In this study, the operation of npn-type GaN-based heterojunction bipolar transistors with different net acceptor concentrations in p-base regions was simulated. It was confirmed that there is a critical net acceptor concentration (NA-ND) depending on the thickness of the base region and that if the NA-ND is lower than the critical value, the collector current may anomalously increase, regardless of base current injection. This phenomenon is caused by the punch-through process via the depletion layer extending from the collector–base junction. The effect of the valence band energy offset at the emitter-base heterojunction (ΔEV) on the current gain (β) was also investigated, and the results showed that β peaks when ΔEV is 0.22–0.30 eV. This is determined by the balance between the hot-electron injection and thermal diffusion processes in the electron transport from the emitter to the base.

GaN-Based Double-Heterojunction Bipolar Transistors With a Composition Graded p-InGaN Base

The influence of energy band structure on the electrical characteristics of GaN-based double-heterojunction bipolar transistors (DHBTs) has been studied through both simulation and fabrication. According to the simulation result, a novel DHBT structure with a composition graded base was grown and fabricated. A long minority carrier lifetime of 4.08 ns has been achieved for the composition graded p-InGaN base with a greatly improved material quality. The indium composition grading of the p-InGaN base layer combined with Si doping profile tuning for the collector layer was proposed to eliminate the energy barrier usually formed at the conventional GaN/InGaN/GaN base–collector (B–C) junction interface due to the band discontinuity and polarization effect. As a result, the as-fabricated DHBT presents a high intercept voltage of 225 V extracted from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{I}_{\textit{C}}$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{CE}}$</tex-math> </inline-formula> curves and a high current gain of 49.

Применение компаундных нефтесодержащих собирателей в процессе пенной сепарации алмазов

The object of this study is the process of diamond-containing kimberlites’ enrichment by foam separation. The subject of research is compound collectors for diamond flotation. The purpose of the study is to substantiate the possibility and choice of conditions for the use of Machchobin oil as a component of the base collector in the foam separation of diamonds. The objectives of the research are to establish the physico-chemical characteristics of Machchobin oil, fuel oil and their mixtures; assess their collecting ability; select the optimal composition of the collector; determine the effectiveness of a compound collector use in the technological process. The methods of rectification analysis of fractional composition, visiometric analysis of structure and phase composition, vibrational viscometry have been used to establish the physical and chemical characteristics of Machchobin oil, fuel oils and their mixtures. To estimate the collecting ability of the compound collector the methods of flotation and foam separation of diamonds and minerals of kimberlite on the laboratory installations of foamless flotation and foam separation have been applied. To determine the efficiency of the compound collector an automated foam separation unit has been used. Conducted physico-chemical studies have shown that when mixing fuel oil F-5 and degassed Machchobin oil, the dissolution of asphaltenes of fuel oil in low–molecular fractions of oil, and paraffins of oil – in medium-molecular fractions of fuel oil is observed. The formation of finely dispersed and colloidal solutions of high-molecular components of oil increases the adhesive activity and leads to an increase in the collecting capacity of the compound collector. The flotation studies have shown that the greatest extraction of diamonds into concentrate is achieved when using a mixture of fuel oil F-5 and Machchobin oil as a base collector at a ratio from 3:1 to 1:1. The tests carried out during the enrichment of the ore of the Aihal tube by foam separation have established an increase in diamond extraction using a compound collector by 1.1–2.1 %. By replacing the fuel oil fraction with oil, a reduction in reagent costs has also been achieved.

The Flotation and Adsorption Characteristics of Albite and Quartz with Oleic Acid Base Collector

The Flotation and Adsorption Characteristics of Albite and Quartz with Oleic Acid Base Collector

A 5.9 mW E-/W-Band SiGe-HBT LNA With 48 GHz 3-dB Bandwidth and 4.5-dB Noise Figure

The theory, design, and implementation of a millimeter-wave (mm-wave) two-stage common-emitter (CE) low noise amplifier (LNA) using a 130-nm silicon-germanium (SiGe):C Bipolar CMOS technology is presented. The LNA was optimized for wideband performance from 62 to 110 GHz for both mm-wave radar/sensing and wireless communication applications. A two-stage broadband noise and impedance matching technique is used to obtain a relativity flat gain (13.5 dB) and noise figure (NF) (4.5 dB) across the E-/W-band. Low-voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(V_{\text {CC}}=0.7\,\,\text {V})$ </tex-math></inline-formula> and low-power (5.9 mW) operation is achieved by forward biasing the base–collector junction, while the wideband capability is further improved by a T-type input matching network utilizing constant quality factor curves. To the best of authors’ knowledge, the presented LNA has the widest 3-dB bandwidth with the lowest power consumption in the literature for silicon-based E-/W-band LNAs.

Heterojunction bipolar transistor featuring a stressed implanted collector: Defects formation and impact on functionality

Optimization of Heterojunction Bipolar Transistors is crucial for improving RF capabilities of modern BiCMOS technologies. Fully-implanted collectors are meant to reduce fabrication complexity and Super Shallow Trench Isolation (SSTI) structures are used to reduce the consequent high base–collector capacitance. Ion implantation can induce lattice defects in silicon and carbon plus phosphorus co-implantation helps reducing them, even if it cannot avoid formation of dislocations generated by bad recrystallization of the implantation-induced amorphous silicon layer. Defects within the device are known to impact functionality and must be avoided. Understanding of the interaction between implantation-induced amorphization and substrate stress due to isolation structures is required for ensuring a reliable integration. Amorphous layer positioning with respect to substrate surface is investigated as the main defect-generation mechanism. Incomplete surface amorphization is shown to induce multiple types of dislocations affecting device functionality. Total surface amorphization ensures almost ideal current characteristics. Silicon clusters appear at high phosphorus/carbon ratios with no impact on functionality. Stress induced by isolation structures is not responsible for dislocations generation but modulates speed of the recrystallization fronts, impacting defects placement.

Heterojunction bipolar transistors with a planar‐type extended base as a hydrogen‐sensitive sensor

A hydrogen sensing transistor fabricated by a heterojunction bipolar transistor (HBT) with an extended base (EB) formed by a metal–semiconductor–metal (MSM) hydrogen sensor is reported. The power consumption in stand-by mode is smaller than 2 µW. Common-emitter characteristics show that the sensing base (collector) current gains at 25°C in 0.01%, 0.1%, and 1% H2/N2 are as high as 75 (512), 134, (977), and 233 (2.89 × 103), respectively. Low-power consumption and high-sensitive gains are indicative that our HBT together with planar-type MSM sensor is very promising for applications to hydrogen sensing transistors using one voltage source.

X-ray diffraction imaging of fully packaged n-p-n transistors under accelerated ageing conditions.

X-ray diffraction imaging was used to monitor the local strains that developed around individual n-p-n bipolar transistors within fully encapsulated packages under conditions of extremely high forward bias to simulate accelerated ageing. Die warpage associated with the packaging was observed to relax systematically as the polymer became viscous due to the temperature rise associated with the dissipation of heat in the transistor. The direct image size and intensity from the individual transistors were interpreted in terms of a model in which local thermal expansion is treated as a cylindrical inclusion of distorted material, contrast arising principally from lattice tilt. The extension of the thermal strain image along the emitter with increasing power dissipation was ascribed to the effect of current crowding in the emitter region. Weaker large-area contrast associated with the base-collector region was interpreted as arising from the smaller change in effective misorientation at the high X-ray energy of thermal lattice dilation in the base region.

Temperature-dependent DC and small signal performance of InGaAs/InP DHBT

Temperature-dependent DC and small-signal analysis have been carried out on 0.7 μm × 15 μm InGaAs/InP double heterojunction bipolar transistors over a temperature range of 25 °C–125 °C by on-wafer S-parameter measurements up to 50 GHz. The thermal behavior of DC and equivalent circuit parameters along with their temperature coefficients were analyzed and reported for the first time using the same InP-based DHBT. Most of the DC parameters show a negative with temperature, for example the temperature coefficients of the VBE,on and VBC,on are −1.4 and −1.48 mV/°C, respectively. And the peak current gain declined from 44.04 to 36.09 with the temperature increased from 25 °C to 125 °C. On the other hand, most of the small-signal parameters show a positive trend with temperature, except for the intrinsic base resistance Rbi, intrinsic base–collector capacitance Cbc, intrinsic base–emitter capacitance Cbe, and common-base current transport factor α0. The results will provide valuable references and insights for future design optimizations of temperature susceptible circuits.

Optical modeling of corrugation cavity receiver for large-aperture solar parabolic dish collector

ABSTRACT This article presents an optical investigation of a corrugation cavity receiver for a 100 m2 parabolic dish collector (PDC). The performance of PDC depends on the selection of the receiver and its mounting distance from the collector base (H) to receive a high amount of reflected radiation. This work performs optical modeling for PDC with a designed corrugation cavity receiver using commercial software, ASAP® 2013. The motivation for this study is derived from the fact that the entrapped internal reflection within the receiver optimizes the system’s optical efficiency. The receiver geometry is such that it attributes to increasing internal reflection and average heat flux intensification. The present optical model is validated with the available literature. The influential geometrical and optical parameters of the receiver have been optimized by simulation by varying the aperture diameter (da,r) from 0.504 to 0.604 m, surface absorptivity (α) from 75 to 95%, receiver coil’s outer and inner pitch (Po and Pi) from 0.00667 to 0.00909 m, and angle of taper (θi) from 50° to 56° for H = 5.35–5.65 m. The performance of the optimized receiver is compared with the conical cavity receiver and is found to be excellent among all values of H. This optical modeling can be expected to be helpful for engineers and researchers in designing the optimized optical receiver for solar parabolic dish collector systems.

Analytical Modeling of Tunnel-Junction Transistor Lasers

Compared with transistor lasers (TLs), tunnel-junction transistor lasers (TJTLs) are more easily modulated with the voltage across base-collector (BC) junction. In this work, the charge-control model and modified rate equation of TJTLs which includes the Franz-Keldysh effect and direct tunneling is developed. We conduct DC and AC analysis with our model and show that the doping concentration in the BC junction plays a key role in the capability to voltage modulate TJTLs since it affects the junction field. A trade-off between the optical power and capability of the voltage modulation emerges as a concern for designing the doping concentration. We also study the effect of the quantum well (QW) position. The result shows that the QW closer to the BC junction can obtain a higher confinement factor to achieve better output power and modulation bandwidth.

Investigation of Base Transport Mechanism in Silicon-Germanium Heterojunction Bipolar Transistor Operating over Wide Temperature Range

A high breakdown voltage silicon-germanium heterojunction bipolar transistor operated over a wide temperature range from 300 K to 10 K has been investigated. The measured Gummel characteristics illustrate that the collector current and base current both shift to the higher voltage as the temperature decreases. The fT/fmax are extracted to be 23/40 GHz at 300K, 28/40 GHz at 90 K, and 25/37GHz at 10K, respectively. The effective amplification range becomes narrow as the temperature decreases. And the ideality factor of base current in the low current region is shown to be temperature-dependent and its value is much larger than 2 at cryogenic temperatures. This phenomenon indicates that the base current is not only contributed by drift, diffusion, and Shockley-Read-Hall recombination, but also by trap-assisted tunneling. The Hurkx local trap-assisted tunneling has been used to analyze the non-ideal base transport mechanism. And a calibrated TCAD device model is developed to further verify this non-ideal transport mechanism.

A 25-GSa/s InP DHBT Track-and-Hold Amplifier Using Active Peaking Input Buffer

In this letter, we present a 25-GSa/s wideband track-and-hold amplifier using 0.8- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> indium phosphide (InP) process for high-speed analog sampling front-end. In this design, an active peaking input buffer is first used in the base–collector switching diode sampler. Moreover, it is carefully calculated and analyzed. The dominant pole in the signal path of the circuit is canceled by one zero produced by the active peaking structure; therefore, the bandwidth (BW) is extended. The experimental results show that a total harmonic distortion (THD) of less than −27 dBc and a spurious-free dynamic range (SFDR) of better than 32.5 dB are demonstrated at a 25-GSa/s sampling rate. In the hold mode, the isolation is better than −42 dB. In addition, it has an 0.156 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f_{T}}$ </tex-math></inline-formula> BW from dc to 25 GHz within 160-GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f_{T}}$ </tex-math></inline-formula> , which is a very competitive value compared with other reported track-and-hold amplifiers (THAs) using the InP process.

Study on Selection of a Suitable Material and The Parameters for Designing a Portable Flat Plate Base-Thermal Cell Absorber (FPBTCA)

Several types of flat plate solar collectors have been designed and developed with various technical parameters involved in the design. The inappropriate flat plate solar collector parameter design and material chosen will affect its performance. Investigation on the effect of flat plate absorber collector material, glass thickness, air gap distance, thermal cell absorber thickness, and flat plate absorber base collector thickness on the performance of solar thermal collectors was conducted in this work. The experiment was performed using the solar simulator with solar radiation of 450 and 750 W/m2. The flat plate absorber collector materials used in this experiment were stainless steel 304 and aluminum. The glass thickness used in this experiment was 2.0, 3.0, 4.0, 5.0, and 10.0 mm. The air gap between the flat plate absorber and glass used in this experiment was 0, 5.0, 10.0, 20.0, and 30.0 mm. The stainless steel thermal cell absorber thickness applied in this experiment was 0.5, 1.0, and 2.0 mm. Meanwhile, the aluminum flat plate base absorber base collector thickness was 0.5, 0.8, and 1.0 mm. The results showed that the 2.0 mm glass thickness has the maximum flat plate absorber temperature (88.1 oC at t = 600 s), high heat gain rate (0.097 oC/s), and the highest total heat gain (1207.33 J). The results also revealed that the air gap distance of 10 mm achieved the maximum flat plate absorber temperature (64.6 oC at t = 600 s), the highest heat gain rate (0.058 oC/s), and the highest total heat gain (4750.92 J). The stainless steel thermal cell absorber thickness of 1.0 mm has the thermal cell absorber temperature of 76.2 oC at t = 600 s and a high heat gain rate at 0.08 oC/s. The aluminum flat plate base absorber achieved the highest flat plate absorber temperature (67.2 oC at t = 600 s) and the highest heat gain rate (0.062 oC/s). By using double glass as glass cover increase the flat plate absorber temperature (76.3 oC at t = 600 s) and the highest heat gain rate (0.077 oC/s). This research aims to produce a flat plate absorber with better energy storage, i.e., the performance of the stainless steel plate absorber is better than aluminum with the same thickness. Although the stainless steel flat plate absorber collector showed a lower temperature than aluminum, it has a higher temperature drop than the latter.

Impact of Work Function Engineering in Charge Plasma Based Bipolar Devices

In this paper, we have explored and justified the reason behind the degradation in the cutoff frequency of the bipolar transistors evolved from the charge plasma concept. It has been observed that if the work function difference present between the emitter metal contact and silicon is greater than or equal to 0.68 eV (ϕm - ϕSI = 4.05 eV - 4.73 eV), it results in increment in the base width which is the inverse of the cutoff frequency. On top of this, two dimensional TCAD simulations of the different bipolar devices also demonstrate the same basewidth widening effect into the intrinsic region which is presentbetween the base region and collector region. Apart from this, if this difference is exactly equal to 0.5 eV (ϕm - ϕSI = 4.23 eV - 4.73 eV) then the base width widening effect can be completely eliminated from the bipolar devices base on the charge plasma.

Verification of a Fabless Device Model Using TCAD Tools: from Bipolar Transistor Formation to I-V Characteristics Extraction

This paper describes the analysis of processes used in microand nanoelectronic device manufacturing. It also presents an exemplary and novel laboratory exercise in which an epitaxial planar n + pn bipolar transistor with junction isolation is illustrated and analyzed stepbystep. Only seven photolithography steps are used to obtain this bipolar transistor structure: for buried layer formation, for junction transistor isolation and collectors regions formation, for base region formation, for emitter and collector n+ region formation, for contact windows, for first aluminum metallization, and, finally, for passivation. Silvaco TCAD software tools are used to implement all of these manufacturing processes and to simulate the resulting IV characteristics of all presented semiconductor structures. This type of laboratory work provides students with basic knowledge and a consistent understanding of bipolar transistor manufacturing, as well as facilitating theoretical understanding, analysis, and simulation of various semiconductor manufacturing processes without the need for costly and lengthy technological manufacturing experiments. This article also presents the conclusions and other benefits of such laboratory work, as well as possible recommendations for further improvement or expansion.