Phosphorus Diffusion Research Articles

Oxygen precipitation behavior and its influence on phosphorus gettering in Czochralski silicon

This study investigates the effects of single-step and two-step annealing processes on the formation of oxygen precipitates and their impact on metal impurity gettering in gallium-doped monocrystalline silicon. The research focuses on the competitive relationship between internal gettering by oxygen precipitates and external gettering through phosphorus diffusion. Experimental results show that two-step annealing generates larger and more abundant oxygen precipitates, enhancing the internal gettering effect and reducing the recovery of minority carrier lifetime after phosphorus gettering. Despite this, phosphorus diffusion gettering remains effective in improving minority carrier lifetime, although the degree of improvement depends on the size and quantity of oxygen precipitates. These findings offer valuable insights for optimizing the fabrication process of silicon-based solar cells.

Re-evaluating the diffusivity of phosphorus in olivine: Implications of low diffusive mobility for thermochronology

Heterogeneities in the phosphorus (P) content of olivine are relatively resistant to diffusive homogenization when compared with other compositional heterogeneities. Thus, heterogeneities in the spatial distribution of P can preserve petrological information about olivine crystals from the earliest stages of crystallization which have been otherwise eliminated. However, compared to independent determinations of protracted cooling timescales in slowly cooled rocks, P enrichments are so sharp as to suggest a rate of diffusive mobility that is many orders of magnitude slower than previously suggested. Here, we heat single natural olivine crystals with sharply defined P heterogeneities (0.02–0.15 wt% P2O5 over 0.5 μm spatial scale) in a 1-atmosphere gas-mixing furnace for durations of 10–20 days at 1400°C, thus exposing them to conditions that should be sufficient for complete diffusive relaxation according to published P diffusivity values. However, high-precision chemical analysis of the same interior section before and after heating reveals no discernable difference in the sharpness of phosphorus concentration patterns. Therefore, diffusion chronometry applied to skeletal P enrichments in olivine currently provides erroneously short diffusive timescales. We discuss several possible causes for these discrepancies and the implications for diffusion chronometry as applied to phosphorus in olivine.

Improving the performance of industrial TOPCon solar cells through the insertion of intrinsic a-Si layer

Passivating contact solar cells have gradually become the mainstream cell technology due to their excellent performance, and further improving the conversion efficiency has become a focus of subsequent research. Typically, achieving excellent field-effect passivation and low contact resistivity in doped polycrystalline silicon (poly-Si) requires heavy phosphorus doping. However, this approach can lead to a predicament wherein excessive phosphorus diffuses into the silicon (Si) substrate during annealing, consequently causing recombination losses. In response to this challenge, a structure incorporating an intrinsic amorphous silicon (a-Si (i)) layer within the passivation layers has been introduced. The primary objective of this structure is to retard the diffusion of phosphorus into the Si substrate. This study entails comprehensive characterizations to delve into the underlying mechanisms of films with the integrated a-Si (i) layer, including surface microscopy, active dopants profile, crystallographic structure, elemental distribution, and electrical properties. Finally, we have fabricated the industrial-sized TOPCon solar cells with an average efficiency of 23.83 %, which is 0.25 % higher than that of Baseline counterparts (23.58 %) on the production line. The above results have demonstrated the introduction of a-Si (i) film can be a buffer layer, retarding the diffusion of phosphorus into the Si substrate and obtaining a better passivation effect, enabling us to further tailor the doping profile for high-efficiency solar cells. Our work highlights a promising strategy to improve the performance of TOPCon solar cells, showcasing the substantial potential for implementation in industrial manufacturing.

A novel phosphorus diffusion process for front-side P–N junction fabrication in PERC solar cells

P–N junction technology underlies photovoltaic conversion in passive emitter and rear cell (PERC) solar cells. Although the front-side phosphorus diffusion method for creating P-type PERC cells is well researched, avenues for innovation persist. We introduce a P–N junction fabrication technique for PERC solar cells via precisely controlling the surface doping concentration and junction depth. Through pressure modulation and carefully selected annealing duration at a defined temperature, the technique yields a P–N junction with a surface doping concentration of 2.37 × 1020 cm−3 and a junction depth of 0.29 μm on the front surface of PERC cells. Compared to conventional diffusion processes, our approach results in an average increase of 1.3 mV in open-circuit voltage, 20 mA in short-circuit current, and an efficiency gain of 0.05 %. The maximum efficiency achieved is 23.68 %, representing an improvement of 0.16 %.

Wintertime diffusion of sedimentary phosphorus – implications for under-ice phosphorus removal from eutrophic lakes

PurposeMany eutrophic lakes are located in regions where lakes become ice-covered during the winter. This study aimed to find out if phosphorus (P) could be withdrawn from such lakes by utilizing the wintertime accumulation of P to the near-bottom water.MethodsData for water quality and sediment characteristics were collected from two eutrophic boreal lakes with tube samplers and sediment corers. Diffusion rates of P across the sediment-water interface (SWI) and within the active sediment layers, and potential export of P via wintertime withdrawal were calculated.ResultsIn the stratifying Lake Kymijärvi, P concentration in the near-bottom water reached 66 µg L−1 and P diffusion across SWI in the hypoxic area 5.4 mg m−2 d−1. In the shallow Lake Savijärvi, maximum P concentration was 78 µg L−1 but P diffusion rate only 0.34 mg m−2 d−1. In Kymijärvi, the concentrations of Fe and Mn in the sediment were high relative to P. In Savijärvi, sediment P was bound to clay minerals and calcium carbonates, while Fe was bound in sulfides.ConclusionIn Kymijärvi, a theoretical14.3% reduction in epilimnetic TP concentration could be achieved in 20 years with 20 L s−1 winter withdrawal. In Savijärvi, 10 L s−1 withdrawal could theoretically cause a 5.8% reduction in TP concentration in 5 years, but the low P diffusion rate across SWI, and the low discharge of the lake may limit P removal. In Kymijärvi, where summertime withdrawal is already applied, additional winter withdrawal could accelerate lake recovery.

Humidity Diode Sensors Based on 1D Nanosized Silicon Structures

Introduction. Humidity measurement is essential in microelectronics, aerospace, biomedical, and food industries, as well as in households for climate control. Currently, various types of devices have been used as humidity sensors: capacitive, resistive, diode, gravimetric, optical structures, field-effect transistors and devices based on surface acoustic waves.Problem Statement. Today, there is a need to develop IC-compatible humidity sensors that have high sensitivityand low cost. To this end, silicon nanowires have been successfully used in resistive and capacitive humidity sensors. However, there is a lack of research on the nanowire effect on device parameters of diode-type humidity sensors.Purpose. To develop diode sensors based on silicon nanowires and to determine the effect of process parameters of synthesis and structural features of nanowires on the performance of humidity sensors.Materials and Methods. The process of sensor fabrication includes several steps: chemical cleaning of silicon wafer, synthesis of silicon nanowires using standard or modified metal-assisted chemical etching, phosphorus diffusion to create a p-n junction, front and back metallization. The surface morphology of the nanostructures has been studied by scanning electron microscopy. The humidity-sensitive characteristics have been studied with theuse of salt hygrostats.Results. It has been shown that the addition of one-dimensional silicon nanostructures to the diode-type sensor signifi cantly improves its characteristics. The rectification ratio increases from 161 to 1807, the response ups from 4.5 to 25, the sensitivity grows from 1.6 to 4.02 (%RH)–1, while the response time and recovery time are reduced from 85/90 to 25/30 s, the hysteresis value goes down from 75 to 16%, the signal deviation after cycling drops from 15to 3%, and the signal fluctuation during continuous device operation decreases from 17 to 15%.Conclusions. The results have shown that the use of a simple and cheap nanowire synthesis technology is effective to produce humidity sensors.

Formation of Selective Emitter from Phosphorus Diffusion By Laser Doping Process

Formation of Selective Emitter from Phosphorus Diffusion By Laser Doping Process

Comprehensive analysis of the corrosion behavior of UG1 phosphate-based ultraviolet glass in water environments

We herein delve into the corrosion dynamics of UG1 in high-temperature water, employing thermal acceleration to expedite reactions. Corrosion-induced changes in spectral properties, optical constants, and morphology are analyzed. The results reveal a phosphorus-poor layer near the surface that affects transmittance, refractive index, and extinction coefficient, with corrosion rates following a parabolic model. This study provides crucial insights for protecting UG1 in humid environments and emphasizes the importance of implementing protective measures against phosphorus diffusion.

Drought accentuates the role of mycorrhiza in phosphorus uptake, part II – The intraradical enzymatic response

Edaphic drought reduces phosphorus (P) diffusivity in soils and arbuscular mycorrhizal fungi (AMF) can compensate for this. We recently showed, along a high-resolution substrate moisture gradient, that AMF effectively deliver P to plants under drought from areas beyond the reach of roots. Here, we investigated how edaphic drought affected the active sites of P exchange between AMF and plants inside the roots using different histochemical stains.Inoculation of dwarf tomato plants (cv. MicroTom) with AMF (Rhizophagus irregularis) slightly increased water retention (decreased the water potential) in substrates, decreased root length, and increased shoot P concentrations compared to non-mycorrhizal plants. Despite their reduced root length, mycorrhizal tomato plants showed a surprisingly congruent physiological drought stress response with their non-mycorrhizal counterparts. However, the activity of alkaline phosphatase (ALP) detected in intraradical fungal structures decreased significantly as soil and xylem water potentials decreased. The decline of ALP activity with increasing drought intensity was accompanied by a reduction of elevated P concentration benefits in shoots of mycorrhizal plants compared to non-mycorrhizal plants.Therefore, we conclude that edaphic drought can restrict the nutritional advantages that plants receive from AMF at the root-fungal interface. This is one of the direct consequences of drought.

Fabrication and characterization of silicon SPADs with doping compensated avalanche region

The features of avalanche region are of importance of SPAD. An ideal broad and rectangular avalanche field may reduce dark count rate but could hardly be realized by actual fabricating technology. We propose a new fabrication process including successive boron and phosphorus diffusions for building special doping compensated avalanche region. A low dark count rate below 10 cps at −20 °C and high photon detection efficiency about 70% at 850 nm are achieved. The afterpulsing probabilities are 2.3% at 20 °C and 3% at 0 °C. FWHM of time resolution is 340ps.

Production of upgraded metallurgical-grade silicon for a low-cost, high-efficiency, and reliable PV technology

Upgraded metallurgical-grade silicon (UMG-Si) has the potential to reduce the cost of photovoltaic (PV) technology and improve its environmental profile. In this contribution, we summarize the extensive work made in the research and development of UMG technology for PV, which has led to the demonstration of UMG-Si as a competitive alternative to polysilicon for the production of high-efficiency multicrystalline solar cells and modules. The tailoring of the processing steps along the complete Ferrosolar’s UMG-Si manufacturing value chain is addressed, commencing with the purification stage that results in a moderately compensated material due to the presence of phosphorous and boron. Gallium is added as a dopant at the crystallization stage to obtain a uniform resistivity profile of ∼1 Ω cm along the ingot height. Defect engineering techniques based on phosphorus diffusion gettering are optimized to improve the bulk electronic quality of UMG-Si wafers. Black silicon texturing, compatible with subsequent gettering and surface passivation, is successfully implemented. Industrial-type aluminum back surface field (Al-BSF) and passivated emitter and rear cell (PERC) solar cells are fabricated, achieving cell efficiencies in the range of those obtained with conventional polysilicon substrates. TOPCon solar cell processing key steps are also tested to further evaluate the potential of the material in advanced device architectures beyond the PERC. Degradation mechanisms related to light exposure and operation temperature are shown to be insignificant in UMG PERC solar cells when a regeneration step is implemented, and PV modules with several years of outdoor operation demonstrated similar performance to reference ones based on poly-Si. Life cycle analysis (LCA) is carried out to evaluate the environmental impact of UMG-based PV technology when compared to poly-Si-based technology, considering different scenarios for both the manufacturing sites and the PV installations.

Phosphorus emitter profile control for silicon solar cell using the doss diffusion technique

The Doped Oxide Solid Source (DOSS) diffusion technique is well suited for fine-tuning of the surface concentration. The dopant surface concentration is important during phosphorus emitter diffusion due to the opposite requirements of a lowly doped emitter for good blue response and a sufficiently high surface concentration for a good ohmic contact. The sources are made in the laboratory using the standard POCl3 diffusion technique. DOSS Diffusions were carried out in the temperature range 850-1050°C using sources with different doping levels obtained by varying the POCl3 partial pressure from 0.004 % to 4.28 %. The electrical profiles were measured using the Stripping Hall profiling technique. Phosphorus diffusion profiles with the complete elimination of the dead layer have been obtained over a large range of source concentrations for all investigated diffusion temperatures. The residual diffusion oxide thickness increased with both temperature and source doping level within the range 7.5-30 nm. XPS profiling indicated that the composition of the residual glass was a mixture of P2O5 and SiO2.

Phosphorus dissolution and diffusion from struvite and its impact on phosphorus availability in Acrisol and Cambisol soils

AbstractThere is a growing interest in recovering and recycling phosphorus (P) from waste streams to reduce reliance on finite and non‐renewable phosphate rock in agriculture. Struvite, derived from waste streams, has emerged as a potential alternative P fertilizer. However, its behaviour in soil remains unclear. This study aimed to investigate the behaviour and effectiveness of struvite as a P fertilizer in acidic Acrisol and calcareous Cambisol soils, focusing on the P dissolution from struvite, struvite P diffusion in soil and P availability. Our findings revealed that the P dissolution from struvite in solution is pH‐dependent, with the most dissolution observed at pH 4.5 and significantly less at pH 7.0 and pH 8.5. Consequently, P dissolution from struvite was more rapid in the Acrisol compared with the Cambisol. This was supported by the increased accumulation of water‐soluble P in the Acrisol and acid‐extractable P in the Cambisol within the 0–1 cm concentric soil section surrounding the struvite application site, as demonstrated in the petri dish experiment. However, the Acrisol exhibited a gradual decrease in P diffusion over time, in contrast to the Cambisol, which showed an increasing trend. This can be attributed to the stronger P fixation observed in the Acrisol. The application of struvite resulted in increased soil P availability, as determined by the diffusive gradients in thin films (DGT) technique, particularly in the Acrisol where struvite was concentrated. Furthermore, the presence of organic acids enhanced struvite P availability in both Acrisol and Cambisol soils. These findings contribute to a better understanding of struvite behaviour in different soil environments and provide valuable insights for optimizing its use as a sustainable and efficient P fertilizer.

Influence of silicon characteristics on the parameters of manufactured photonics cells

The paper investigates the influence of the electrophysical characteristics of silicon on the final parameters of photoelectronic elements using p-i-n photodiodes as an example. It has been found that photodiode samples made on the basis of silicon with a higher resistivity are more prone to the formation of inversion channels at the oxide-semiconductor interface. Also, the dark current and responsivity of such photodiodes reach saturation at a lower voltage. It has also been shown that silicon-based photodiodes with a longer lifetime of non-basic charge carriers have lower dark current values. It has been shown that products with crystallographic orientation [111] have a much lower density of surface dislocations after technological operations than in the case of silicon with orientation [100]. It was also found that materials with different crystallographic orientations have different phosphorus diffusion coefficients. It has been experimentally established that a silicon oxide film grows faster on the surface of crystallographic orientation silicon [111] than on the surface of crystallographic orientation silicon [100]. This is due to the difference in the surface density of silicon atoms inherent in different crystallographic planes.

Reduction of phosphorus diffusion in bulk germanium via argon/phosphorus co-implantation and RTA annealing

Germanium has received increased research interest for use in next-generation CMOS technology as its high carrier mobilities allow for enhanced device performance without further device scaling. Fabrication of high-performance NMOS Ge devices is hindered by high diffusivity and low activation of n-type implanted dopants. While the high solid solubility of P in Ge makes it an ideal dopant, its diffusion mechanism is poorly understood and results in heavy tradeoffs between implanted dopant diffusion and electrical activation. In this study, we demonstrate the suppression of in-diffusion of implanted P via a co-implantation with Ar. Diffusivity of implanted P species and their activation is investigated over a wide range of annealing temperatures and times. P diffusion was explored by secondary-ion-mass-spectrometry and the diffusivity of P was extracted by solving the 2D diffusion equation using the Crank–Nicolson method, and the dopant electrical activation was extracted from the Hall effect measurements. The co-implantation of P with Ar entirely suppresses P in-diffusion up to annealing temperatures as high as 700 °C but at the cost of its reduced electrical activation. Extracted diffusivity reveals a highly correlated exponential relationship with annealing. P activation energy was extracted from Arrhenius behavior. A 450 °C/10 min annealing of P implant shows negligible in-diffusion of P with the activation as high as 70%. RTA processing of the Ar/P co-implanted sample at 750 °C for 1 min results in a negligible P in-diffusion and an electrical activation of 20%.

Geochemical dynamics of phosphorus and metals in sediments of a shallow coastal lake (Xuño Lake, Galicia-NW Iberian Peninsula)

The shallow lakes are important freshwater ecosystems, since they support much of biodiversity and ecosystem services of life on land. Shallow lakes are highly dynamic ecological entities that can exist in several alternative stable states through regime shift caused by a natural or human disturbance that exceeds ecological thresholds for biological communities composition and structure equilibria. The sediment as a reservoir has a key role in the limnological regulation of wetlands linked to the fluxes of nutrients and elements in the biogeochemical interplay with the water and macrophytes. For this reason, the role of sediment in the limnology of the shallow coastal lake of Xuño (NW Iberian Peninsula) was explored by seasonally monitoring the chemical composition of water and sediments, also according to macrophyte species. The shallow depth determines the high availability of light in the bottom and a well-mixed water column maintain the surface of the water–sediment interface oxygenated. The oxic conditions of the bottom implies a top-down regulation of the water column in the Xuño shallow lake that limits the diffusion of phosphorus and trace metals (Fe, Mn, Cu, and Co) to the water, buffering eutrophication or contamination levels by immobilization in the sediments. In fact, the concentration of Hg in the lake water in spring, and also its bioavailability, are high due to its release from the sediment in suboxic conditions. The cover of helophyte species Phragmites Australis and Schoenoplectus Lacustris showed differences in the assimilation of organic monoester and diester phosphorus forms in the sediment. However, the water of the Xuño Lake shows an eutrophic status by the nutrient input associated with the birds populations as indicated by microbiological data.

Atomically Resolved Interfacial Analysis of Bone‐Like Hydroxyapatite Nanoparticles on Titanium

Titanium is commonly used for medical devices, including osseointegrating implants, owing to its biocompatibility and mechanical properties. Nanostructuring titanium implants is known to enhance the healing process by promoting bone growth on the implant surface. Hydroxyapatite nanoparticles, resembling natural bone mineral, have been used to further improve osseointegration. While previous studies have investigated the osseointegration of titanium implants using atom probe tomography, limited research has focused on the attachment of synthetic hydroxyapatite to titanium. Herein, electron microscopy and atom probe tomography are used to reveal the assembly of synthetic hydroxyapatite nanoparticles in the titanium oxide surface. By sputter coating with chromium, a suitable matrix is formed for detailed interfacial analysis. The results demonstrate the diffusion of calcium, phosphorus, and carbon from hydroxyapatite nanoparticles into the titanium oxide surface.

High-efficiency n-TOPCon bifacial solar cells with selective poly-Si based passivating contacts

Improving the conversion efficiency of n-TOPCon solar cell is still a hot topic. The selective poly-Si based passivating contacts (Poly-SEs) are ideal candidates for reducing the parasitic absorption and contact resistivity of n-type silicon solar cells and for providing better current collection. In this work, we used LPCVD and the POCl3 tube furnace diffusion methods to fabricate the selective poly-Si based passivating contacts, and studied the influences of key process parameters of the SiOx layer formation process (the oxidation duration (toxidation) and the constant pressure duration (tpressure)), and POCl3 tube diffusion process parameters (the POCl3-N2 carrier gas flow rate at the deposition, deposition temperature, drive-in temperature) on the n+-poly-Si profiles, recombination current density (J0), contact resistivity (ρc) of n-TOPCon solar cells. The results showed that the toxidation and tpressure had a significant impact on J0 and ρc which were mainly related to the distribution number of O and Si4+ content on the growth of the SiOx layer. And the influence of the drive-in temperature of phosphorus (P) diffusion process on J0 value is stronger than that of the deposition temperature, which was mainly related to the chemical passivation of SiOx layer induced by P-indiffusion into Si at high temperature. The reduction in the thickness of poly-Si from 110 nm to 30 nm led to an increase in the short-circuit current density (Jsc) per nanometer of ∼0.0093 mA/cm2 per nm. The Poly-SEs were fabricated by 3D printing mask technology and secondary LPCVD/phosphorus diffusion with J0, n+ ≈ 5 fA/cm2 (n+-poly-Si layer ≈ 50 nm) and J0, metal,n++ ≈ 73.8 fA/cm2 (n++-poly-Si layer ≈ 110 nm), and the efficiency was improved by 0.12% owing to the increase in Jsc value of 0.28 mA/cm2. After optimizing the passivation process, the industrial-grade TOPCon bifacial cells reached an efficiency (Eff), Voc, Jsc, and FF values as high as 25.4%, 721 mV, 42.2 mA/cm2, and 83.5%, respectively.

Influence of Structural Defects on the Electrophysical Parameters of pin-Photodiodes

The results of studies of electrophysical parameters of pin-silicon-based photodiodes, depending on their operating modes (external bias and temperature), manufactured on single-crystal silicon wafers of p-type conduction orientation (100) with ρ = 1000 ohm cm, are presented. The p+-type region (isotype junction) is created by the implantation of boron ions; the n+-type region, by the diffusion of phosphorus from the gas phase. It is established that on the voltage-current characteristics under reverse bias, three regions of dark cur-rent variation depending on the applied voltage can be distinguished, sublinear, superlinear, and linear, caused by various mechanisms of the generation-recombination processes in the depletion region of the pn-junction. A noticeable dependence of the barrier capacitance value (at a frequency of 1 kHz) and the size of the depletion region on temperature is observed only when the applied reverse voltages do not exceed the contact potential difference (V ≤ 1 V).

Технологія кремнієвих p-i-n фотодіодів зі зменшеною кількістю термічних операцій

The main parameters of the p-i-n photodiodes (PD) are responsivity, dark current and capacity of responsive elements (RE). To ensure the maximum values of the specified parameters, it is necessary to use defect-free silicon with the maximum values of resistivity and life time of minor charge carriers. These characteristics of the starting material degrade during high-temperature thermal operations. Therefore, it is worth using a technology that allows you to avoid the degradation of silicon characteristics. This can be implemented by reducing the temperature of diffusion and oxidation operations, as well as by reducing the number of actual thermal operations. The samples were made according to two versions of the technology: diffusion-planar using two-stage diffusion of phosphorus from planar sources, and mesotechnology using one-stage diffusion of phosphorus using liquid PCl3 diffusant. After manufacturing, the PD parameters were compared. The use of mesotechnology with one-stage diffusion of phosphorus made it possible to reduce the number of thermal operations by two times compared to serial technology. The experimental samples had a pulse responsivity at a wavelength of 1.064 μm of 0.47-0.50 A/W, and the serial ones had a responsivity of 0.45-0.48 A/W. The difference in responsivity is caused by the difference in the life time of minor charge carriers, since in the case of the proposed technology, the degree of degradation of the life time of minor charge carriers during the manufacturing process is smaller. After selective etching, it was seen that when using a liquid diffusant, the density of dislocations on the crystal surface is much higher than when using planar sources of phosphorus. Due to the higher density of dislocations, the experimental samples had higher dark currents, but when using a low bias voltage, the difference in dark currents is insignificant. The RE capacity of the experimental samples was slightly lower than that of the serial ones. This can be explained by the difference in the resistivity of the i-region of the final crystals.