Base Doping Research Articles

Design of Fluorescence Enhancing Sensor for Mercury Detection via Bamboo Cellulose-Derived Carbon Dots.

Mercury contamination of the environment is extremely hazardous to human health because of its significant toxicity, especially in water. Biomass-derived fluorophores such as carbon dots (CDs) have emerged as eco-friendly and cost-effective alternative sensors that provide comparable efficacy while mitigating the environmental and economic drawbacks of conventional methods. In this work, we report the fabrication of a selective fluorescence-enhancing sensor based on sulfur-doped carbon dots (SCDs) using waste bamboo-derived cellulose and sodium thiosulfate as the soft base dopant, which actively complexes with mercury ions for detection. SCDs with an average size of 4 nm were synthesized hydrothermally, and the sulfur doping was confirmed quantitatively with an atomic percentage of 6.5%. Optical studies reveal an abnormal fluorescence enhancement of SCD in the presence of mercury due to the aggregation of carbon dots via sulfur-containing functional groups. The fabricated sensor exhibits a low detection limit of 5.16 nM, suggesting its application potential as a reliable mercury sensor. Real-time analyses carried out using tap water samples spiked with mercury and industry samples showed high efficiency for Hg(II) detection. The sensing performance was also demonstrated by using SCD-coated filter paper strips.

Ultrahigh-performance heterojunction bipolar phototransistor enabled by bilateral piezoelectric charge modulation effect

Heterojunction photodiodes based on p-n junction with enhanced piezo-phototronic effect have been extensively studied. However, the photoresponsivity of conventional photodiodes is small due to the natural zero current gain. Heterojunction phototransistor usually has greater photoresponsivity due to the non-zero current gain. More importantly, heterojunction phototransistor owns two interfaces, offering the opportunity to introduce the bilateral piezoelectric charge modulation effect for further performance enhancement compared to the conventional single-interface piezo-phototronic effect in photodiode. In this work, a base-floating heterojunction bipolar phototransistor (FHPT) based on n-ZnO/p-Si/n-ZnO structure with a spectral detection range from ultraviolet (UV)–visible is demonstrated. The positive piezoelectric charge generated at the two interfaces of the collector junction and the emitter junction, combined with the optimal base width and low resistance base doping concentration of the FHPT, leads to an excellent photoresponsivity (18046 A/W, 365 nm), high detectivity (5.7×1012 Jones), and a wider modulation (7120 %). The physical mechanism leading to the ultrahigh performance is attributed to the cooperative positive piezoelectric charge at the two interfaces, simultaneously reducing the effective base width and lowering the emitter junction barrier. This work illustrates the regulation of heterojunction phototransistor performance by the bilateral piezoelectric charge modulation effect, providing insightful guidance to high-performance phototransistor design.

Modeling and simulation of a high power InGaP/GaAs heterojunction alphavoltaic battery irradiated by americium-241

The design of semiconductor-based heterojunction structures can be turned useful to raise the efficiency of nuclear micro-batteries. In this study, we have investigated a micro-power alphavoltaic battery by using a lab-made software. The nuclear battery consists of an In0.49Ga0.51P/GaAs heterostructure irradiated by americium-241 (Am241) alpha particles with an average kinetic energy of 5.485 MeV. The alphavoltaic battery exhibits an overall active area of 1 cm2. Based on a comprehensive analytical model, the device current density-voltage J(V) and output electric power P(V) characteristics are simulated extracting the energy conversion efficiency. The model takes into account the reflection of the incident alpha particles, the ohmic losses, the effect of the boundary between the two layers, and the depletion region borders. Different values of the radioisotope apparent activity density, the emitter and base dopant concentrations, and the surface recombination velocities in both the front and back layers are considered during the simulations to optimize the battery performance. The present study reports that by irradiating by a 2.4 mCi/cm2 Am241 source, the obtained energy conversion efficiency of the battery can reach 10.31% with a maximum output power density of 16.07 µW/cm2. Therefore, In0.49Ga0.51P/GaAs heterostructure coupled with Am241 seems a promising design for long-term energy supply in harsh environments.

Investigation of manganese doped BaSe for energy harvesting and spintronics devices

Abstract The incorporation of magnetism to a solid material may drastically alter its electrical transport behavior, providing a way to modify the magneto-optoelectronic and thermoelectric features that have recently drawn a lot of scientific attention. In this regard, we utilized density function theory (DFT) based full potential linearized augmented plane wave (FP-LAPW) approach to study doping effect of Mn on physical characteristics of barium selenide (BaSe). Pristine BaSe is nonmagnetic semiconductor with indirect bandgap of 2.11 eV. Concentration dependent Mn doping in BaSe introduces spin polarized intermediate bands in the vicinity of Fermi level primarily composed of Mn-3d orbitals. Asymmetric band profiles indicate the ferromagnetic semiconductor nature of of Mn doped BaSe compounds. Total magnetic moment value of 5.0 μ B, 10.0 μ B, and 20.0 μ B are obtained for corresponding Ba1−xMnxSe (x = 6.25%, 12.5%, 25%) systems. Furthermore, the analysis of optical and thermoelectric characteristics reveals the importance of studied alloy for application in advanced technologies including low energy light absorbers and thermoelectric generators.

Exploring the Potential of Pure Germanium Kesterite for a 2T Kesterite/Silicon Tandem Solar Cell: A Simulation Study.

Recently, the development of tandem devices has become one of the main strategies for further improving the efficiency of photovoltaic modules. In this regard, combining well-established Si technology with thin film technology is one of the most promising approaches. However, this imposes several limitations on such thin film technology, such as low prices, the absence of scarce or toxic elements, the possibility to tune optical properties and long lifetime stability. Therefore, to show the potential of kesterite/silicon tandems, in this work, a 2 terminal (2T) structure using pure germanium kesterite was simulated with combined SCAPS and transfer matrix methods. To explore the impact of individual modifications, a stepwise approach was adopted to improve the kesterite. For the bottom sub cell, a state-of-the-art silicon PERC cell was used with an efficiency of 24%. As a final result, 19.56% efficiency was obtained for the standalone top kesterite solar cell and 28.6% for the tandem device, exceeding standalone silicon efficiency by 4.6% and justifying a new method for improvement. The improvement observed could be attributed primarily to the enhanced effective lifetime, optimized base doping, and mitigated recombination at both the back and top layers of the CZGSSe absorber. Finally, colorimetric analysis showed that color purity for such tandem structure was low, and hues were limited to the predominant colors, which were reddish, yellowish, and purple in an anti-reflective coating (ARC) thickness range of 20-300 nm. The sensitivity of color variation for the whole ARC thickness range to electrical parameters was minimal: efficiency was obtained ranging from 28.05% to 28.63%.

Design and Performance Enhancement of a GaAs-Based Homojunction Solar Cell Using Ga0.5In0.5P as a Back Surface Field (BSF): A Simulation Approach

The GaAs semiconductor is a solar energy promising material for photovoltaic applications due to its good optical and electronic properties. In this work, a homojunction GaAs solar cell with AlxGa1-xAs and GayIn1-yP solar energy materials as window and back surface field (BSF) layers, respectively, was simulated and investigated using SCAPS-1D software. The performance of the GaAs-based solar cell is evaluated for different proportions ofxandy, which allowed us to obtain the values of 0.8 and 0.5 forxandy, respectively, as the best values for high performance. We then continued the optimization by taking into account some parameters of the solar cell, such as thickness, doping, and bulk defect density of the p-GaAs base, n-GaAs emitter, and Ga0.5In0.5P BSF layer. Solar cell efficiency increases with emitter thickness, but the recombination phenomenon is more pronounced than that of electron-hole pair generation in the case of a thicker base. The effect of variation in the work function of the back contact has also been studied, and the best performance is for a platinum (Pt) electrode. The optimized GaAs-based solar cell achieves a power conversion efficiency of 35.44% (JSC=31.52 mA/cm2,VOC=1.26 V,FF=89.14%) and a temperature coefficient of -0.036%/°C. These simulation results provide insight into the various ways to improve the efficiency of GaAs-based solar cells.

MINORITY CARRIERS DENSITY AND RECOMBINATION VELOCITY AT THE BACK FACE OF N+PP+ SILICON SOLAR CELL: EFFECTS OF DOPING RATE AND TEMPERATURE

In this article, we have established the expressions of the density of minority charge carriersand the recombination velocity at the back face of our sample.The effects of the base doping rate combined with the effects of temperature on the latter have been the subject of our study.Thus, we followed the evolution of the density of minority charge carriers and of the recombination velocity at the back face as a function of the thickness of the base for different base doping rate and for different values of the temperature.

Optimisation of extrinsic base doping of a SiGe heterojunction bipolar transistor integrated in a BiCMOS 55 nm technology for high frequency performances

Optimisation of extrinsic base doping of a SiGe heterojunction bipolar transistor integrated in a BiCMOS 55 nm technology for high frequency performances

Current-voltage characteristics of silicon solar cells: Determination of base doping concentration and hysteresis correction

The measurement of the current-voltage ( IV ) characteristics is the most important step for quality control and optimization of the fabrication process in research and industrial production of silicon solar cells. The occurrence of transient errors and hysteresis effects in IV -measurements can hamper the direct analysis of the IV -data of high-capacitance silicon solar cells. We propose a novel procedure to reconstruct a quasi-steady-state (qss) IV -characteristics from hysteretic measurements by aligning the generalized current density of forward and backward sweeps. In the process, the base doping concentration N B and the cell thickness d are used as optimization parameters and calculated alongside the qss- IV -curve. We summarize the theory behind the method, describe the experimental implementation and verify the applicability of the approach by comparing the extracted doping concentration to multiple alternative methods. For a test set of more than 100 silicon heterojunction solar cells with doping concentrations between 3 and 7∙10 15 cm -3 a RMSD <3.4∙10 14 cm -3 is achieved. Basic parameter extraction from the qss- IV -curve closely match reference values with a RMSD <0.1 % abs in efficiency and fill factor. • Procedure for hysteresis correction proposed and analyzed. • Successful alignment of hysteretic forward and backward IV -curves. • Base doping concentration, resistivity and cell thickness extracted from hysteresis. • Inline capability at high accuracy without additional hardware demonstrated. • Procedure retroactively applicable to existing data to correct transient errors.

Simulation Analyses of High‐Efficiency Monolithic Solar Cells with Reduced Shunt and Lateral Forward Bias Current

Larger solar cells are preferred for higher power output. However, they produce higher current and lead to higher ohmic loss. This loss has prompted manufacturers to laser cut cells into halved cells, resulting in lower current, higher voltage string‐cells. While these techniques reduce ohmic loss, they introduce cutting‐edge recombination. The monolithic solar cell resembles halved cell but without requiring cutting the original cell into strings of cells which saved the cutting‐edge recombination loss. However, we observed that the interconnection of base regions of the string‐cells on the same wafer leads to problems such as lateral forward bias current, resulting in severe degradation of the fill factor (FF) and open‐circuit voltage (VOC). Solutions to these issues are proposed including depassivated surfaces between string‐cells, optimized spacing between the string‐cells, lowered base doping density, thinner wafers, and shading regions between the string‐cells. According to simulation results, these methods could increase the efficiency of the monolithic cell to very close to the baseline cell. With the consideration of the reduced shading, ohmic loss, and module blank areas on the cell‐to‐module process, the efficiency of a module with monolithic cells could exceed that of a module with baseline cells or a module of halved/shingling cells.

Bicyclic-ring base doping induces n-type conduction in carbon nanotubes with outstanding thermal stability in air

The preparation of air and thermally stable n-type carbon nanotubes is desirable for their further implementation in electronic and energy devices that rely on both p- and n-type material. Here, a series of guanidine and amidine bases with bicyclic-ring structures are used as n-doping reagents. Aided by their rigid alkyl functionality and stable conjugate acid structure, these organic superbases can easily reduce carbon nanotubes. n-Type nanotubes doped with guanidine bases show excellent thermal stability in air, lasting for more than 6 months at 100 °C. As an example of energy device, a thermoelectric p/n junction module is constructed with a power output of ca. 4.7 μW from a temperature difference of 40 °C.

In0.3Ga0.7As heterojunction bipolar transistor grown on GeSi substrate for high-frequency application

We report an In0.3Ga0.7As HBT device grown on a 200 mm Si wafer using GeSi as virtual starting substrate and InAlAs as the compositionally graded buffer layer from GaAs to In0.3Ga0.7As lattice constant. A DC gain, emitter-base, and base-collector ideality factors of 10, 1.43, and 1.56, respectively, are obtained for a device with an emitter area of 40 × 50 μm2. Small-signal simulation of an In0.3Ga0.7As HBT device with 2 × 8 μm2 emitter area shows that current gain cutoff frequency (fT) and maximum cut-off frequency (fMax), of 50 GHz and 220 GHz, respectively, can be achieved with base doping and layer thickness of 2 × 1018cm−3 and 30 nm, respectively.

Design, realization and loss analysis of efficient low-cost large-area bifacial interdigitated-back-contact solar cells with front floating emitter

Large-area (251.96 cm 2 ) bifacial interdigitated-back-contact (IBC) solar cells are presented in this work. We employ front floating emitter (FFE) to replace the front surface field (FSF) to simplify the process sequences. A simplified process flow is exploited to fabricate the IBC solar cells through industrial equipment and compatible processes. Double side boron diffusion followed by etch-back to form the emitter and lightly doped front surface, reducing high-temperature influence on the bulk lifetime and fabrication complexity. Ion implantation and anneal process is applied for base doping. The cell conversion efficiency reaches 22.92%, independently certificated by Fraunhofer Institute for Solar Energy System CalLab (Fraunhofer ISE). The IBC solar cells feature an open metallization grid, which offers a bifacial response with the bifaciality reaches to 72%. Only one-step mask and opening procedure was used, which greatly simplified the process. These results demonstrate the feasibility of this simplified process for manufacturing low-cost high-efficiency of IBC cells. Key parameters such as surface recombination J 0 , metal contact recombination J 0-metal , contact resistivity of the cells are extracted by specially designed structures. Loss analysis shows that further efficiency improvement can be attained though reducing the contact resistance and metal contact recombination. The results in this work indicates the potential of this novel process for producing low-cost high-efficient IBC solar cells. Large-area efficient IBC solar cells are fabricated by using front floating emitter (FFE), which reducing the process complex and save cost. With the simplified process, the conversion efficiency of 22.92% and bifaciality of 72% are attained. Through special structures and patterns designing, the performance parameters ( J 0 , J 0-metal , and ρ c ) are investigated, and the losses of the IBC cell are analyzed by numerical simulation. • Large-area bifacial interdigitated back contact (IBC) solar cell are fabricated through industrial equipment. • Front floating emitter (FFE) replace of FSF reduce electrical shading effect increase the process tolerance. • Front side etch back to from FFE, ion-implantation to from BSF simplified the process of IBC cell. • Extract key parameters ( J 0 , J 0-metal , ρ c ), Quokka 3D simulator was performed to estimate the performance of solar cell. • The front efficiency is 22.92% and 16.54% on the back, the bifaciality is 72%.

GeSn (0.524 eV) single-junction thermophotovoltaic cells based on the device transport model

Based on the transport equation of the semiconductor device model for 0.524 eV GeSn alloy and the experimental parameters of the material, the thermal–electricity conversion performance governed by a GeSn diode has been systematically studied in its normal and inverted structures. For the normal p+/n (n+/p) structure, it is demonstrated here that an optimal base doping N d(a) = 3 (7) × 1018 cm−3 is observed, and the superior p+/n structure can achieve a higher performance. To reduce material consumption, an economical active layer can comprise a 100 nm–300 nm emitter and a 3 μm–6 μm base to attain comparable performance to that for the optimal configuration. Our results offer many useful guidelines for the fabrication of economical GeSn thermophotovoltaic devices.

Influence of base doping level on the npn microstructure solar cell performance: A TCAD study

Silicon industry has a mature learning curve which is the driver for 90% share of the PV market. Yet, the cost/m 2 of the planar crystalline silicon solar cell is still high. To reduce the cost of silicon-based solar cells, heavily doped wafers can be used in a proposed npn microstructure in which photoexcited carries are vertically generated while the collection of carriers is accomplished in the lateral direction. In this work, we report on the influence of the heavily p + base doping concentration, N a , on the performance of the cell for different base widths. All simulations are performed by using SILVACO TCAD under AM1.5 illumination. The results show that for N a extending from 5 × 10 17 cm −3 to 2 × 10 19 cm −3 , the cell could achieve a competitive efficiency, from 15.4% to 9%, respectively. • Device simulation of proposed npn microstructure solar cell was comprehensively performed. • The impact of base high doping on the device performance was fully discussed. • The results show that for N B ranging from 5 × 10 17 cm −3 to 2 × 10 19 cm −3 , the cell could achieve a competitive efficiency, from 15.4% to 9%, respectively. • For base doping ranging from 5×10 17 cm -3 to 2×10 19 cm -3 , a competitive efficiency is 15.4% to 9%, respectively.

Individual Energetic Processes Efficiencies in a Polycrystalline Silicon PV Cell Versus Electromagnetic Field

The Photovoltaic (PV) system is often installed near the telecommunication antenna without takes account the performance degradation that the electromagnetic field can cause. The present work provides the recognition about the greatest losses occur which can cause the overall efficiency drop. In fact, the absorption and the thermodynamic processes are more sensitive to the variation of the electromagnetic field more than FF and thermalization processes in presence of the electromagnetic field. The absorption and thermodynamic mechanism are the main cause of the degradation of the polycrystalline silicon PV cell outputs. The PV cell having height base doping level to get a better resistivity to the electromagnetic field must be chosen to improve theses outputs. Then a low electromagnetic field zones must be searched to install the PV system improving its electrical production performance.

Design and novel turn-off mechanism in transistor lasers

We provide a quantitative analysis of the spontaneous recombination time in the quantum well (QW) of a transistor laser (TL) that shows that owing to the heavy doping in the base of the transistor, Auger recombination is responsible for the short carrier lifetime and low quantum efficiency of the device. By taking advantage of the QW location close to the collector in the TL three-terminal configuration, we devise a new turn-off mechanism that results in quick electron tunneling through the QW barrier by applying a high base-collector reverse bias to deplete the QW and suppress further recombination. For practical base-collector reverse bias, tunneling time from the QW is on the order of 10th of picosecond, which with a lighter base doping density would simultaneously achieve a fast TL turn-off response, while reducing Auger recombination.

Cryogenic Diode Thermometer Insensitive Completely to Magnetic Fields Up to 1 T

The article presents investigation results concerning silicon p-n junction diodes with heightened diode base doping level up to a critical value for the insulator-metal transition. Accent is made on application of such the diodes as temperature sensors in cryogenic region and in the presence of magnetic fields, i.e. under conditions when available commercial silicon diode temperature sensors become inapplicable. The reason is a freezing-out of the free current carriers in their lightly doped bases. In this case the base conduction becomes hopping with large magnetoresistance, and an impact ionization of the frozen-out carriers in the electric field results in electrical instability (hysteretic phenomena in the current-voltage characteristics). It is shown that the diodes investigated are free of the electrical instabilities inherent in the commercial diodes, and can operate with much lower the sensor working currents. The lower the operating current, the smaller is the measurement error connected with magnetic-field influence. At the operating currents of 10 and 1 μA, the sensor proves to be insensitive completely to magnetic fields up to 1 T.

The effect of dopant material to optical properties: energy band gap Tin Oxide thin film

The synthesis of the SnO2 thin film with doped materials of aluminum, fluorin indium, a combination of aluminum and indium, a combination of aluminum and fluorine, an a combination of the three doping agents, namely aluminum, fluorine, and indium have be successfully carried out. The purpose of this synthesis is to determine the effect of the vario doping materials on the resulting bandgap energy value. The thin layer was synthesized usi the sol-gel spin coating technique with the ratio of the base material and doping material us were 95: 5% and 85: 15%. The results showed that the higher the doping materi concentration, the resulting bandgap energy value decreased. In addition, the highest bandg energy value is found in the SnO2 thin film with indium doping, namely for direct 3.62 eV (9 5% percentage) and 3.59 eV (percentage 85: 15%), while the indirect bandgap energy value 3, 92 eV (percentage 95: 5%) and 3.67 eV (percentage 85: 15%). The lowest energy band g value is found in the SnO2 thin film with a combination of the three doping aluminum, fluorin and indium, namely for direct 3.50 eV (95: 5% percentage) and 3.41 eV (percentage 85: 15% while the energy band gap value is indirect. namely 3.81 eV (percentage 95: 5%) and 3.55 e (percentage 85: 15%). All the energy band gap range in semiconductor materials.

Performance analysis of infrared heterojunction phototransistors based on Type-II superlattices

In this study, a comprehensive analysis of the n-p-n infrared heterojunction phototransistors (HPTs) based on Type-II superlattices has been demonstrated. Different kinds of Type-II superlattices were carefully chosen for the emitter, base, and collector to improve the optical performance. The effects of different device parameters include emitter doping concentration, base doping concentration, base thickness and energy bandgap difference between emitter and base on the optical gain of the HPTs have been investigated. By scaling the base thickness to 20 nm, the HPT exhibits an optical gain of 345.3 at 1.6 μm at room temperature. For a 10 μm diameter HPT device, a −3 dB cut-off frequency of 5.1 GHz was achieved under 20 V at 150 K.