Behavior Of Carriers Research Articles

Controlled phase distribution of quasi-2D perovskite enables improved electroluminescence

Quasi-two-dimensional (quasi-2D) perovskites are increasingly explored for integration into light-emitting diodes (LEDs) as light-emissive layers. However, the quasi-2D perovskite films likely exhibit non-uniform dimensional phase distribution and irregular internal crystal structures. These characteristics are known to contribute to undesirable effects, including non-radiative recombination losses and radiative recombination in perovskites of various dimensions, impeding the realization of efficient electroluminescence and high color purity in LEDs. In this study, we present an investigation on the correlation between the dimensional distribution of quasi-2D perovskites and charge carrier behavior by modulating anti-solvent dripping during the film fabrication processes. We provide a comprehensive analysis of the impact of controlled dimensional distribution on charge injection and recombination processes associated with the performance of quasi-2D perovskite LEDs. Our work emphasizes the crucial role played by controlled dimensionality in quasi-2D perovskites in realizing efficient and stable perovskite-based LEDs.

Performance of β-carotene-loaded nanostructured lipid carriers under dynamic in vitro digestion system: Influence of the emulsifier type.

A better understanding of how emulsifier type could differently influence the behavior of nanostructured lipid carriers (NLC) under the gastrointestinal digestion process, as well as at the cellular level, is of utmost importance for the NLC-based formulations' optimization and risk assessment in the food field. In this study, NLC composed by fully hydrogenated soybean and high-oleic sunflower oils were prepared using soy lecithin (NLC Lβ) or Tween 80 (NLC Tβ) as an emulsifier. β-Carotene was entrapped within NLC developed as a promising strategy to overcome β-carotene's low bioavailability and stability. The effect of emulsifier type on the digestibility of β-carotene-loaded NLC was evaluated using an in vitro dynamic digestion model mimicking peristalsis motion. The influence of β-carotene-loaded NLC on cell viability was assessed using Caco-2 cells in vitro. NLC Tβ remained stable in the gastric compartment, presenting particle size (PS) similar to the initial NLC (PS: 245.68 and 218.18nm, respectively), while NLC Lβ showed lower stability (PS>1000nm) in stomach and duodenum phases. NLC Tβ also provided high β-carotene protection and delivery capacity (i.e., β-carotene bioaccessibility increased 10-fold). Based on the results of digestion studies, NLC Tβ has shown better physical stability during the passage through the in vitro dynamic gastrointestinal system than NLC Lβ. Moreover, the developed NLC did not compromise cell viability up to 25µg/mL of β-carotene. Thus, the NLC developed proved to be a biocompatible structure and able to incorporate and protect β-carotene for further food applications. PRACTICAL APPLICATION: The findings of this study hold significant implications for industrial applications in terms of developing nanostructured lipid carriers from natural raw materials widely available and used to produce other lipid-based products in the food industry, as an alternative to synthetic ones. In this respect, the β-carotene-loaded NLC developed in this study would find a great industrial application in the food industry, which is in constant search to develop functional foods capable of increasing the bioavailability of bioactive compounds.

Photoexcited Carrier Dynamics in Iodine-Doped CH3NH3PbBr3 Single Crystals.

Iodine-doped bromide perovskite single crystals (IBPSCs) have important applications in optoelectronic fields, such as in solar cells. Currently, much research has aimed to study the phase separation phenomenon and device performance improvements in IBPSCs. However, important intrinsic photoexcited carrier dynamics are often overlooked in IBPSCs. Here, we explored the photoexcited carrier dynamics in typical iodine-doped MAPbBr3 single crystals using the excitation intensity-dependent steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) technique. We found that the trap state density changes with an increase in the amount of doped iodine. Further, we noticed that there is an influence of carrier diffusion on the photoexcited carrier dynamics, and then, we evaluated the carrier diffusion coefficients and recombination constants via numerical simulations of the PL kinetics. Consequently, we found that the electron shallow trap-related carrier behaviors substantially impacted the PL kinetics. Our results greatly facilitate a deeper understanding of the fundamental characteristics of mixed halide perovskite material.

Organic Ligand Engineering for Tailoring Electron-Phonon Coupling in 2D Hybrid Perovskites.

In the emerging two-dimensional organic-inorganic hybrid perovskites, the electronic structures and carrier behaviors are strongly impacted by intrinsic electron-phonon interactions, which have received inadequate attention. In this study, we report an intriguing phenomenon of negative carrier diffusion induced by electron-phonon coupling in (2T)2PbI4. Theoretical calculations reveal that the electron-phonon coupling drives the band alignment in (2T)2PbI4 to alternate between type I and type II heterostructures. As a consequence, photoexcited holes undergo transitions between the organic ligands and inorganic layers, resulting in abnormal carrier transport behavior compared to other two-dimensional hybrid perovskites. These findings provide valuable insights into the role of electron-phonon coupling in shaping the band alignments and carrier behaviors in two-dimensional hybrid perovskites. They also open up exciting avenues for designing and fabricating functional semiconductor heterostructures with tailored properties.

Molecular Intercalation‐Induced Two‐Phase Evolution Engineering of 1T and 2H‐MS2 (M = Mo, V, W) for Interface‐Polarization‐Enhanced Electromagnetic Absorbers

AbstractPolarization at interfaces is an important loss mechanism for electromagnetic wave (EMW) attenuation, though the motion behavior of carriers in interfaces composed of different types of conductors has yet to be investigated. Tuning the phase structure of transition metal dichalcogenides (TMDs) MS2 (M = Mo, V, W) by organics small molecule intercalation to achieve the modulation of interfacial types is an effective strategy, where 1T‐MS2 exhibits metallic properties and 2H‐MS2 has semiconducting properties. To exclude the contribution of the intrinsic properties of TMDs materials, three TMDs (MoS2, VS2, and WS2), which also possess phase transitions, are investigated. Among them, the 1T‐MS2 composite exhibits excellent EMW absorption performance under the synergistic effect of interfacial polarization and conduction loss. 1T‐MoS2/MOF‐A exhibits the best EMW absorption performance with an RLmin of −61.07 dB at a thickness of 3.0 mm and an EAB of 7.2 GHz at 2.3 mm. The effectiveness of the modulation of the interfacial polarization using 1T‐phase and 2H‐phase MS2 is demonstrated, which is important for the analysis of the carrier motion behavior during the interfacial loss.

Toward Gigahertz Photodetection with Transition Metal Dichalcogenides.

ConspectusTransition metal dichalcogenides (TMDCs) exhibit favorable properties for optical communication in the gigahertz (GHz) regime, such as large mobilities, high extinction coefficients, cheap fabrication, and silicon compatibility. While impressive improvements in their sensitivity have been realized over the past decade, the bandwidths of these devices have been mostly limited to a few megahertz. We argue that this shortcoming originates in the relatively large RC constants of TMDC-based photodetectors, which suffer from high surface defect densities, inefficient charge carrier injection at the electrode/TMDC interface, and long charging times. However, we show in a series of papers that rather simple adjustments in the device architecture afford TMDC-based photodetectors with bandwidths of several hundreds of megahertz. We rationalize the success of these adjustments in terms of the specific physical-chemical properties of TMDCs, namely their anisotropic in-plane/out-of-plane carrier behavior, large optical absorption, and chalcogenide-dependent surface chemistry. Just one surprisingly simple yet effective pathway to fast TMDC photodetection is the reduction of the photoresistance by using light-focusing optics, which enables bandwidths of 0.23 GHz with an energy consumption of only 27 fJ/bit.By reflecting on the ultrafast intrinsic photoresponse times of a few picoseconds in TMDC heterostructures, we motivate the application of more demanding chemical strategies to exploit such ultrafast intrinsic properties for true GHz operation in real devices. A key aspect in this regard is the management of surface defects, which we discuss in terms of its dependence on the layer thickness, its tunability by molecular adlayers, and the prospects of replacing thermally evaporated metal contacts by laser-printed electrodes fabricated with inks of metalloid clusters. We highlight the benefits of combining TMDCs with graphene to heterostructures that exhibit the ultrafast photoresponse and large spectral range of Dirac materials with the low dark currents and high responsivities of semiconductors. We introduce the bulk photovoltaic effect in TMDC-based materials with broken inversion symmetry as well as a combination of TMDCs with plasmonic nanostructures as means for increasing the bandwidth and responsivity simultaneously. Finally, we describe the prospects of embedding TMDC photodetectors into optical cavities with the objective of tuning the lifetime of the photoexcited state and increasing the carrier mobility in the photoactive layer.The findings and concepts detailed in this Account demonstrate that GHz photodetection with TMDCs is feasible, and we hope that these bright prospects for their application as next-generation optoelectronic materials motivate more chemists and material scientists to actively pursue the development of the more complicated material combinations outlined here.

Scavenging Energy and Information through Dynamically Regulating the Electrical Double Layer

AbstractThe electrical double layer (EDL) between solids and liquids serves as the primary interface for ionic‐electronic coupling and is pivotal in nanoscale phenomena, governing electric field effects, ion transport, surface interactions, etc. Dynamically regulating the EDL through mechanical or electrostatic methods can influence charge carrier behavior, thereby impacting energy scavenging and storage processes. This regulation enabled efficient energy scavenging by governing ionic migration and optimizing charge carrier concentration at the interface, presenting a novel avenue to achieve efficient energy and information flow. Here, various scavenging energy and information devices through dynamically regulating the EDL are systematically reviewed. They are classified into three groups by regulating the distribution and movement of charge carriers throughout the entire EDL, diffuse layer, and Debye length range. The review provided a comprehensive overview of the operating principles, influencing factors, output characteristics, and typical applications, along with a discussion on future challenges. This holistic examination offers researchers valuable insights for evaluating their applicability in various scenarios.

Investigation of AC and DC Electrical Conductivity in Ethyl Cellulose (EC) and Poly Methyl Methacrylate (PMMA) Polyblends

The study of AC and DC electrical conductivity is crucial for understanding the behavior of charge carriers within materials and their mobility. Ethyl cellulose (EC) stands out among cellulose ethers due to its favorable electrical, mechanical, and weathering properties. Poly Methyl Methacrylate (PMMA) is a thermoplastic known for its rigidity, transparency, and outdoor durability, making it a valuable material. Despite being insulating materials, both EC and PMMA exhibit limited free charge carriers and low mobility. In this research, AC and DC electrical properties of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blends doped with tetrahydrofuran (THF) film were investigated using isothermal evaporation techniques. The investigation focused on the effects of temperature, electric field, and frequency on electrical conduction mechanisms. Measurements were conducted across frequencies ranging from 1 KHz to 1 MHz at temperatures between 323 K and 373 K. Results indicate that AC electrical conductivity of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blend (EC/PMMA) increases with higher frequencies of the applied electric field. Meanwhile, DC electrical conductivity of Ethyl Cellulose (EC), Poly Methyl Methacrylate (PMMA), and their blend (EC/PMMA) rises with increasing temperature. X-ray diffraction (XRD) analysis further supports these conductivity changes in the blend.

A nonlocal photoacoustic effect with variable thermal conductivity of semiconductor material subjected to laser heat source

This study explores the behavior of laser-exposed photo-excited carriers, investigating the propagation of photoacoustic waves in the thermoelastic domain. It also delves into the theoretical generation of surface acoustic waves in semiconductors through photo-thermoelastic processes. The research considers the interaction between thermomechanical and acoustic waves in a nonlocal medium with temperature-dependent thermal conductivity. Unlike relying on electron–phonon or electron-hole thermalization processes, photoacoustic waves here result from thermoelastic stress induced by the laser-induced temperature increase. The investigation accounts for the optical, mechanical, and thermoelastic properties of nanoscale semiconductor materials. Predictions of photoacoustic signals are derived by solving a combined thermal diffusion issue and a thermoelastic problem, using Laplace and Fourier transforms in the mathematical model. Numerical solutions encompass various physical fields within the time domain using the inversion technique of Laplace and Fourier transforms, such as thermal, acoustic, mechanical, and carrier density diffusion. The study evaluates and compares the influences of thermal memory and thermal conductivity presenting visual representations.

Type-dependent hot carrier behavior in photoelectrochemical reduction and oxidation of Au/GaN junction photoelectrodes

In junctions with semiconductors, plasmonic metal nanoparticles (NPs) can be utilized to efficiently harness solar energy by collecting hot carriers. However, the behavior of hot carriers at the interfaces between semiconductors with opposite doping types is not fully elucidated. Here, Au NPs are attached to n-doped (Au/n-GaN) or p-doped gallium nitrides (Au/p-GaN) to examine the photoelectrochemical performance regarding hot carrier behavior. Direct surface potential measurements revealed that electrons are collected in n-type GaN (n-GaN) when illuminated, while hot holes remain in Au NPs for oxidation reactions via the plasmonic process. Conversely, holes are collected in p-type GaN (p-GaN), thereby promoting the reduction reaction by the electrons left in Au NPs. Specifically, the change in surface potential difference induced by green light illumination in Au/p-GaN is four times greater than that observed in Au/n-GaN. Conversely, the changes in open-circuit potential and photocurrent density under light illumination are approximately six times more significant in Au/n-GaN compared to Au/p-GaN. This difference in efficiency can be attributed to the more favorable oxidation reaction occurring in Au NPs at the interface with GaN materials, as opposed to the reduction reaction, due to the difference in band alignment between the Au/GaN junction systems.

Enhanced Uranium Extraction via Charge Dynamics and Interfacial Polarization in MoS2/GO Heterojunction Electrodes.

The removal of uranyl ions (UO2 2+) from water is challenging due to their chemical stability, low concentrations, complex water matrix, and technical limitations in extraction and separation. Herein, a novel molybdenum disulfide/graphene oxide heterojunction (MoS2/GO-H) is developed, serving as an effective electrode for capacitive deionization (CDI). By combining the inherent advantages of electroadsorption and electrocatalysis, an innovative electroadsorption-electrocatalysis system (EES) strategy is introduced. This system utilizes interface polarization at the MoS2 and GO interface, creating an additional electric field that significantly influences carrier behavior. The MoS2/GO-H electrode, with its extraordinary adsorption capacity of 805.57mgg-1 under optimal conditions, effectively treated uranium-laden wastewater from a mine, achieving over 90% removal efficiency despite the presence of numerous competing ions at concentrations significantly higher than UO2 2+. Employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, it is found that the MoS2/GO-H total charge density at the Fermi level, enhanced by interfacial polarization, surpasses that of separate MoS2 and GO, markedly boosting conductivity and electrocatalytic effectiveness.

Cocatalyst activity mapping for photocatalytic materials revealed by the pattern-illumination time-resolved phase microscopy.

Photocatalytic water-splitting represents a promising avenue for clean hydrogen production, necessitating an in-depth understanding of the photocatalytic reaction mechanism. The majority of the photocatalytic materials need cocatalysts to enhance the photo-oxidation or reduction reactions. However, the working mechanism, such as collecting charge carriers or reducing the reaction barrier, is not clear because they disperse inhomogeneously on a surface, and it is difficult to follow the local charge carrier behavior. This study employs the pattern-illumination time-resolved phase microscopy (PI-PM) method to unravel the spatial charge carrier behavior in photocatalytic systems, utilizing time-resolved microscopic image (refractive index change) sequences and their clustering analyses. This approach is robust for studying the change in local charge carrier behavior. We studied two major cocatalyst effects on photocatalysts: TiO2 with/without Pt and hematite with/without CoPi. The PI-PM method, supported by charge type clustering and the effects of scavengers, allowed for the analysis of local activity influenced by cocatalysts. This approach revealed that the introduction of cocatalysts alters the local distribution of charge carrier behavior and significantly impacts their decay rates. In TiO2 systems, the presence of Pt cocatalysts led to a local electron site on the micron scale, extending the lifetime to a few tens of microseconds from a few microseconds. Similarly, in hematite films with CoPi, we observed a notable accumulation of holes at cocatalyst sites, emphasizing the role of cocatalysts in enhancing photocatalytic efficiency. The study's findings highlight the complexity of charge carrier dynamics in photocatalytic processes and the significant influence of cocatalysts.

Effect of PLGA raw materials on in vitro and in vivo performance of drug-loaded microspheres.

Poly(lactide-co-glycolide) and poly(lactic-co-glycolic acids) (PLGAs) play a critical role in the development of commercial long-acting injectable microsphere formulations. However, very little information is available describing the impact of PLGA manufacturer and monomer distribution along the polymer chain (e.g., glycolic blockiness (Rc) and average lactic block length (LL)) on the degradation and release behavior of PLGA drug carriers in vitro and in vivo. Here, we compared the in vitro and in vivo performance of (a) four leuprolide-loaded microsphere formulations prepared from similar low-molecular-weight acid-capped PLGAs (10-14 kD, i.e., Expansorb® DLG 75-2A, Purasorb® PDLG 7502A, Resomer® RG 752H and Wako® 7515) and (b) two triamcinolone acetonide-loaded (Tr-A) microsphere formulations from similar medium-molecular-weight ester-capped PLGAs (i.e., Expansorb® DLG 75-4E and Resomer® RG 753S). Lupron Depot® and Zilretta® were used as reference commercial products. The six 75/25 PLGAs displayed block lengths that were either above or below values expected from a random copolymer. Drug release and polymer degradation were monitored simultaneously in vitro and in vivo using a cage implant system. The four leuprolide-loaded formulations showed similar release and degradation patterns with some notable differences between each other. Microspheres from the Expansorb® polymer displayed lower LL and higher Rc relative to the other 3 PLGA 75/25 microspheres, and likewise exhibited distinct peptide release and degradation behavior compared to the other 3 formulations. For each formulation, leuprolide release was erosion-controlled up to about 30% release after the initial burst followed by a faster than erosion release phase. In vitro release was similar as that in vivo over the first phase but notably different from the latter release phase, particularly for the most blocky Expansorb® formulation. The Purasorb® and Wako® formulations displayed highly similar performance in release, degradation, and erosion analysis. By contrast, the two ester-capped Expansorb® DLG 75-4E and Resomer® RG 753S used to prepare Tr-A microspheres shared essentially identical LL and higher Rc and behaved similarly although the Expansorb® degraded and released the steroid faster in vivo, suggestive of other factors responsible (e.g., residual monomer). The in vivo release performance for both drugs from the six microsphere formulations was similar to that of the commercial reference products. In summary, this work details information on comparing the similarities and differences in in vitro and in vivo performance of drug-loaded microspheres as a function of manufacturing and microstructural variables of different types of PLGA raw materials utilized and could, therefore, be meaningful in guiding the source control during development and manufacturing of PLGA microsphere-based drug products. Future work will expand the analysis to include a broader range of LL and higher Rc, and add additional important formulation metrics (e.g., thermal analysis, and residual monomer, moisture, and organic solvent levels).

Performance improvement of GaN-based vertical cavity surface emitting laser by employing a hole storage layer and enhancing the carrier transport behavior

In this paper, the transport behavior of carriers between multiple quantum wells (vertical) and inside a single quantum well (radial) in a GaN-based Vertical Cavity Surface Emitting Laser (VCSEL) is investigated, and a new device structure with a hole storage layer is proposed to enhance the laser performance. The theoretical results indicate that the vertical transport capability of holes is the key factor for total stimulated recombination rate and hole leakage. The VCSEL with a double-QW structure exhibits better output performance compared to the devices with three or more QWs owing to the lower light absorption loss and the stronger optical field in the active region. Furthermore, a thicker undoped GaN layer is proposed to be added as the hole storage layer to mitigate hole leakage for the VCSEL with a double-QW structure. This new structure can increase the tilt of energy band in the region of the hole storage layer and effectively improve the uniformity of radial distribution of holes in QWs. Therefore, it is beneficial to reduce the threshold current and enhance the laser output power.

Lattice dynamics and self-trapped excitons in the Cs2SnBr6 double perovskites

Our study delved into the detailed investigation of Cs2SnBr6 double perovskites, focusing on their electrical properties, lattice dynamics, and stability. The direct bandgap for Cs2SnBr6 was estimated to be at 2.93 eV. One external translational mode of the Cs+ lattice with T 2g symmetry and three internal modes of the octahedral with A 1g, E g, and T 2g symmetries are defined by calculated lattice dynamics, experimental micro-Raman scattering. We show a correlation with first-principles calculations, validating using a band-structured electronic approach to understanding the behavior of charge carriers, and electron–phonon interactions in Cs2SnBr6. We propose that electron-vibration interactions result in self-trapped excitons (STEs) displaying significant Stokes shifts (0.508 eV) and broad-spectrum emission. Understanding the behavior of STEs is fundamental for their optoelectronic applications.

Modularization of Regional Electronic Structure over Defect-Rich CeO2 Rods for Enhancing Photogenerated Charge Transfer and CO2 Activation.

Oxygen vacancy (OV) engineering has been widely applied in different types of metal oxide-based photocatalytic reactions. Our study has shown that the redistributed OVs resulting from voids in CeO2 rods lead to significant differences in the band structure in space. The flat energy band within the highly crystallized bulk region hinders the recombination of photogenerated carrier pairs during the transfer process. The downward curved energy band in the surface region enhances the activation of the absorbents. Therefore, the localization of the band structure through crystal structure regionalization renders V-CeO2 capable of achieving efficient utilization of photogenerated carriers. Practically, the V-CeO2 rod shows a remarkable turnover number of 190.58 μmol g-1 h-1 in CO2 photoreduction, which is ∼9.4 times higher than that of D-CeO2 (20.46 μmol g-1 h-1). The designed modularization structure in our work is expected to provide important inspiration and guidance in coordinating the kinetic behavior of carriers in OV defect-rich photocatalysts.

Insight into the interface effect and PTC effect on the temperature-adaptive electrical conductivity of epoxy composite

Doping functional fillers into the polymeric matrix is an effective strategy to improve the electrical, thermal, and other performance of insulating materials. It is imperative to understand the influence of fillers on the charge carrier behavior to achieve better regulation effectiveness. In this work, micrometer-sized and nano-sized ceramic particles with positive temperature coefficient (PTC) electrical resistivity are employed to prepare the epoxy composites, whose electrical conductivity under different temperature and electric field, space charge characteristics, permittivity, and electric field distribution are studied. It is found that the doping of a PTC filler shifts the electrical conduction from bulk-controlled to electrode-limited, determining the quantity of charge carriers within epoxy composites. While the interface effect mainly affects the transport process of charge carriers, it would fail to dominate the electrical conduction since the abundant charge carrier introduced by the semiconductive functional filler. Combined with the reinforced interface effect, the electrical conductivity–temperature characteristic of the epoxy nanocomposite is optimized, leading to the reduction in the maximum electric field within electrical equipment insulation by 55%. These findings emphasize the synergistic regulation of charge carrier amount and transport, which contributes to the precision design of polymeric composites doped with functional fillers.

Efficacy of a Maillard-type conjugate of whey protein isolate with chitosan as a carrier for a liposomal form of a combination of curcumin and balanced amounts of n-3 and n-6 PUFAs. Part II. Carrier behaviour under simulated in vitro digestion

The study evaluated the benefits of using the whey protein isolate (WPI)–chitosan (CHIT) carrier formed via a Maillard reaction step to enhance the bioavailability of a liposomal form of nutraceuticals during in vitro gastrointestinal digestion according to the INFOGEST protocol. Liposomes appeared uniformly released from their hydrolysed complex [WPI–CHIT]–(PC–FO–CUR) during both the gastric (54 ± 9%) and small intestinal (46 ± 7%) stages in vitro. This was due to the initial encapsulation of liposomes (94%) by both WPI and chitosan in the soluble fraction of the Maillard-type conjugate. During the gastric stage, the mucoadhesiveness of the complex was improved by covalently attaching chitosan to thermally denatured WPI. The WPI denaturation was confirmed by DSC. Furthermore, both components aided in maintaining the complex's mucoadhesiveness during the small intestinal stage. Laser light scattering, TEM, EPRS, and tensiometry characterized interactions of hydrolysed complex particles and liposomes with mucin or bile salts in the GIT in vitro.

The influence of defects on conduction processes in chalcogenide semiconductor compounds

Due to the strong dependence on the intrinsic defectiveness of structures, semiconductor compounds based on metal chalcogenides have a wide spread in kinetic properties and high growth temperatures of materials, as well as a tendency to self-compensation of defects. It has been shown that an increase in defectivity in the cation sublattice leads to a decrease in ionic conductivity in copper chalcogenides, and an increase in temperature leads to an increase in ionic conductivity due to a change in mobility. The low activation energy indicates a strong intrinsic disorder of the cation part of the lattice. In copper chalcogenides, the presence of hopping conductivity at small deviations from stoichiometry is explained by compensation and a high concentration of vacancies. Under such conditions, this activation energy is the activation energy for the movement of copper ions throughout the crystal and almost all metal ions contribute to the ionic electrical conductivity. In semiconductor compounds based on metal chalcogenides with deviations from stoichiometry, the activation energy of cationic conductivity does not change, since the defects that arise in this case do not introduce large changes in ionic conductivity with temperature. The increase in ionic conductivity with increasing temperature is due to a change in mobility, since the carrier concentration remains unchanged. The latter is determined only by the structural features of the phases. Deviation from stoichiometry in compounds makes it necessary to take into account the movement of the main charge carriers in the allowed zones, and the movement of carriers along vacancies. The properties of metal chalcogenides are largely determined by the characteristics of their preparation and depend on the relative ratio of metal and chalcogen atoms, as well as the presence of intrinsic defects and their influence on the mechanism of behavior of charge carriers and transfer phenomena.

Poly-Si/a-Si/4H-SiC p-n heterojunction broadband photodetector prepared by magnetron sputtering

With the increasing complexity of scenarios, there is a growing need for broadband photodetectors (PDs). In this work, we report a polycrystalline-Si (poly-Si)/amorphous-Si (a-Si)/4H-SiC p-n heterojunction PD with efficient response in a broad spectral range of ultraviolet–visible–near-infrared. The poly-Si/a-Si/4H-SiC heterojunction was achieved by magnetron sputtering and annealing. The fabricated heterojunction device has a low dark current of 1 pA at −40 V and a fast response time of 3 ns due to the outstanding rectification characteristics of the heterojunction combined with narrow bandgap and wide bandgap material. In addition, the carrier behavior of the heterojunction exposed to broadband light is analyzed in detail by constructing the energy band diagram.