Narrow Bandgap Semiconductor Material Research Articles

The thermal transport properties of Boron-doped C2N nanoribbons

In this paper, we focus on the thermal spin transport properties of hydrogen-saturated graphene-like nanoribbons substituted for doped nonmetallic B by using density functional theory combined with non-equilibrium Green's function approach. We find that AC2NNR-H(B) is a distinctly narrow bandgap semiconductor material and exhibits significant spin Seebeck effect, temperature switching effect, and giant magnetoresistance. Surprisingly, the spin Seebeck coefficients can reach 1.16 mV/K and the magnetoresistance value not only reaches 108% at low temperature, but also 104% near room temperature. These unique transport properties can be explained using spin-dependent transmission spectra combined with energy band structure. The current work further extends the theoretical study of graphene-like derivatives and provides new ideas for the construction of spintronic devices.

Vacancy-engineered Mn-doped iron oxide nano-crystals for enhanced sonodynamic therapy through self-supplied oxygen

Sonodynamic therapy (SDT) is a minimally invasive therapeutic approach, that uses ultrasound activating sonosensitizers to generate reactive oxygen species (ROS) for inducing the tumor cell death. However, the SDT is always limited by the dissatisfactory performance of sonosensitizers and hypoxic tumor microenvironment (TME). Nano iron oxide is a narrow bandgap semiconductor material with good biocompatibility. The doping of manganese into iron oxide (Mn-doped iron oxide nano-crystals named Mn-Fe2O3 NCs) not only reduced the band gap of iron oxide and altered the valence band position of iron oxide, but also introduced more oxygen vacancies and inhibited the complexation of electrons (e-) and holes (h+), significantly enhancing the ability to generate ROS. The Mn-Fe2O3 NCs improved the hypoxic TME by self-generating oxygen and consuming endogenous glutathione (GSH), which amplified oxidative stress and further enhanced the SDT. The therapeutic results showed that the prepared Mn-Fe2O3 NCs could efficiently inhibit the triple-negative breast cancer (TNBC) cells by SDT (80.49 % inhibition ratio in vivo). Overall, we propose a simple method to design inorganic sonosensitizers for enhancing efficient sonodynamic therapy.

Light elements adsorption modulates the electronic structure of h-BC2N/g-C6N6 nanoribbons

The electronic properties of h-BC2N/g-C6N6 nanoribbons were calculated using the first principles method. Three states of ferromagnetic, antiferromagnetic, and paramagnetic coupling were set. The energy of the ferromagnetic coupling state was found to be the lowest, indicating that the final stable state was the ferromagnetic coupling state. The thermodynamic stability was also verified in the ferromagnetic coupling state. The h-BC2N/g-C6N6 nanoribbons itself is magnetic with a magnetic moment of 2 μB and is a direct narrow band gap semiconductor material. In order to change the electronic properties, six different atoms (B, C, N, Al, Si, P) were adsorbed in the h-BC2N/g-C6N6 nanoribbon, and their band structure and charge density were studied. The results show that the adsorption of different atoms in h-BC2N/g-C6N6 nanoribbons will produce different results. Among them, the adsorption of N and P atoms changes its properties from a semiconductor to a half-metal, which can generate a 100% polarized current in the Fermi surface. This provides more development directions for spintronics devices.

Melt growth of crystalline α-SrSi2 by the vertical Bridgman method and its thermoelectric characteristics

As a candidate thermoelectric material operating in the low-temperature regime (room temperature to 473 K), we have examined α-SrSi2: a narrow bandgap semiconductor material, which is composed of environmentally benign elements. We are able to report the successful production of single-crystalline-like α-SrSi2 with clear semiconducting properties by melting synthesis, a thermodynamically stable and thermally equilibrium process that reduces unexpected process contamination and improves crystallinity.The crystals up to 20 × 20 × 5 mm3 have been obtained for a solid–liquid phase reaction temperature of 1308 K for 10 h with a growth rate averaging at 0.617 K/h in the temperature range from 1403 K to 1373 K. The band gap of this material was measured at 48 meV, which is higher than the values previously reported. The power factor was measured at 2.9 mW/mK2 at 300 K, which is the highest value ever reported for undoped α-SrSi2.Based on the experimental bandgap values, the hybrid functional was used to correct the first-principles calculation method, and the Seebeck coefficient obtained from the first-principles calculation was compared with experimental values. Which values showed good agreement with experimental values.

Multifunctional diamond‐based catalysts: Promising candidates for energy conversions in extreme environments—A mini‐review

AbstractIn order to properly utilize the abundant CO2 and water resources, various catalytic materials have been developed to convert them into valuable chemicals as renewable fuels electrochemically or photochemically. Currently, most studies are conducted under mild laboratory conditions, but for some extreme environments, such as Mars and space stations, there is an urgent need to develop new catalysts satisfying such special requirements. Conventional catalytic materials mainly focus on metals and narrow bandgap semiconductor materials, while the research on wide and ultrawide bandgap materials that can inherently withstand extreme conditions has not received enough attention. Given the robust stability and excellent physico‐chemical properties of diamond, it can be expected to perform in harsh environments for electrocatalysis or photocatalysis that has not been investigated thoroughly. Here, this review summarizes the catalytic functionality of diamond‐based electrodes with various but tunable product selectivity to obtain the varied C1 or C2+ products, and discusses some important factors playing a key role in manipulating the catalytic activity. Moreover, the unique solvation electron effect of diamond gives it a significant advantage in photocatalytic conversions which is also summarized in this mini‐review. In the end, prospects are made for the application of diamond‐based catalysts under various extreme conditions. The challenges that may be faced in practical applications are also summarized and future breakthrough directions are proposed at the end.

Enhanced minority carrier lifetime in bulk hydrogen-passivated InAsSbBi

We investigate the bulk passivation of the dilute bismide alloy InAsSbBi by plasma-assisted hydrogenation. InAsSbBi is of significant interest for mid- to long-wave infrared photodetection due to its bandgap flexibility and potential integration with heterostructured photodetector architectures. Epitaxially grown InAsSbBi samples are characterized by photoluminescence and time-resolved photoluminescence measurements for a range of hydrogenation conditions. Increases in the minority carrier lifetime of over 3× are reported, with no degradation over a period of months following the treatment. Photoluminescence measurements confirm that the hydrogenation process improves the InAsSbBi optical properties. These results offer a path toward the improved performance of InAsSbBi-based photodetectors and potentially other narrow bandgap semiconductor materials and material systems.

Orietation-controlled synthesis and Raman study of 2D SnTe

Tin telluride (SnTe), as a narrow bandgap semiconductor material, has great potential for developing photodetectors with wide spectra and ultra-fast response. At the same time, it is also an important topological crystal insulator material, with different topological surface states on several common surfaces. Here, we introduce different Sn sources and control the growth of regular SnTe nanosheets along the (100) and (111) planes through the atmospheric pressure chemical vapor deposition method. It has been proven through various characterizations that the synthesized SnTe is a high-quality single crystal. In addition, the angular resolved Raman spectra of SnTe nanosheets grown on different crystal planes are first demonstrated. The experimental results showed that square SnTe nanosheets grown along the (100) plane exhibit in-plane anisotropy. At the same time, we use micro-nanofabrication technology to manufacture SnTe-based field effect transistors and photodetectors to explore their electrical and optoelectronic properties. It has been confirmed that transistors based on grown SnTe nanosheets exhibit p-type semiconductor characteristics and have a high response to infrared light. This work provides a new approach for the controllable synthesis of SnTe and adds new content to the research of SnTe-based infrared detectors.

CeVO4 nanoparticle coupled with Ag/AgBr as an efficient plasmonic photocatalyst for degradation of rhodamine B: Construction, characterization, and mechanism insight

The unique characteristics of the surface plasmon resonance effect significantly improve the utilization rate of solar energy and charge separation of narrow band-gap semiconductor materials. In this work, Ag/AgBr/CeVO4 plasmonic photocatalyst was synthesized by the microwave-assisted hydrothermal method, followed by in-situ precipitation and photoreduction process. The as-prepared Ag/AgBr/CeVO4-2.0 composite showed superior photocatalytic efficiency for degradation of rhodamine B (84.2% in 10 min), which was 1.45 and 84.2 times higher than that of Ag/AgBr and pristine CeVO4 nanoparticles (NPS, size 30–50 nm), respectively. Photoluminescence and photocurrent tests indicated the rapid transfer and separation of electron–hole pairs in this plasmonic system, which can be attributed to the localized surface plasmon resonance effect of Ag NPs. In investigations on band structure and radical quenching experiments, a Z-scheme photocatalytic system bridged by the Ag NPs was proposed. This research offers revealing insight into the design and fabrication of the CeVO4 plasmonic photocatalytic system for application in environment purification and remediation.

Bibonding Constructing Coordinatively Unsaturated Zni+(0 < i < 2) Sites for Enhanced Photo‐Fenton Activity

AbstractThe coordinatively unsaturated metal sites (CUMSs) have attracted widespread attention for enhancing catalytic activity. This study reports a controllable “bibonding” method to construct the coordinatively unsaturated Zni+ (0 < i < 2) active sites by forming N(g‐C3N4)‐Zn—N(imidazole) under mild experimental conditions. The catalysts with Zni+ are used for the photo‐Fenton reaction to degrade methylene blue (MB) without any oxidant. The degradation efficiency is positively correlated with Zni+. The Zni+ improved the Fe2+/Fe3+ conversion efficiency and the H2O2 generation ability of the catalyst. The optimized catalysts with 2.27% of Zni+ present a photo‐Fenton degradation efficiency of MB as 73.45 mg g−1 at pH 7 and 78.54 mg g−1 at pH 4. This strategy can be used to construct CUMSs for a series of narrow bandgap semiconductor materials containing nitrogen atoms.

Quantum chemistry simulations in an undergraduate project: tellurophenes as narrow bandgap semiconductor materials

The convenient graphical user-interfaces now available with advanced simulation software offer a powerful didactic tool for research-led teaching of methods in quantum chemistry and wider applications of quantum mechanics. In the student project work reported here, a homologous series of semiconducting chalcogenophenes (encompassing poly-thiophenes, poly-selenophenes and poly-tellurophenes) with varying polymer chain lengths were simulated in detail using density functional theory (DFT). Following geometry optimization, energy calculations reveal that increasing the length of the polymer chain (N) from a monomer to a hexamer leads to a narrowing and large-N convergence of the bandgap. It is found that hexa-tellurophene has significantly favourable electronic properties as compared to the other analogues, with a greatly enhanced electron affinity (−2.74 eV), and a corresponding bandgap energy of 2.18 eV, giving a superior matching to the solar spectrum.

Exploring the photovoltaic capabilities of Sc4C3 MXene using density functional theory

The purpose of this study is to explore the structural and optoelectronic properties of a two-dimensional MXene, Sc4C3 as a viable choice for charge transport layers and absorber layer additive in emerging photovoltaic technologies such as perovskite solar cells (PSCs), employing the principles of density functional theory (DFT) using the WIEN2k tool. The optimized lattice constant of the material and the volume for which the energy is minimum are estimated as 13.66 bohr and 2548.66 bohr3 respectively. The estimation of elastic properties, viz. the bulk modulus, shear modulus and Poisson’s ratio as 115 GPa, 71 GPa and 0.25 respectively, reveals that the material is resistant to deformation. The analysis of electronic properties and band structure indicates that Sc4C3 MXene has a direct bandgap of 0.747 eV at the Г point, and hence can be considered as a narrow bandgap semiconductor material. The study shows that the material possesses optimal light absorption properties with an absorption coefficient, dielectric permittivity and refractive index of 1.84 × 102 cm−1, 19.02 and 4.42 respectively, which are suitable for photovoltaic applications.

2D Ultrawide Bandgap Semiconductors: Odyssey and Challenges.

2D ultrawide bandgap (UWBG) semiconductors have aroused increasing interest in the field of high-power transparent electronic devices, deep-ultraviolet photodetectors, flexible electronic skins, and energy-efficient displays, owing to their intriguing physical properties. Compared with dominant narrow bandgap semiconductor material families, 2D UWBG semiconductors are less investigated but stand out because of their propensity for high optical transparency, tunable electrical conductivity, high mobility, and ultrahigh gate dielectrics. At the current stage of research, the most intensively investigated 2D UWBG semiconductors are metal oxides, metal chalcogenides, metal halides, and metal nitrides. This paper provides an up-to-date review of recent research progress on new 2D UWBG semiconductor materials and novel physical properties. The widespread applications, i.e., transistors, photodetector, touch screen, and inverter are summarized, which employ 2D UWBG semiconductors as either a passive or active layer. Finally, the existing challenges and opportunities of the enticing class of 2D UWBG semiconductors are highlighted.

Ferroelectric polarization effect on the photocatalytic activity of Bi0.9Ca0.1FeO3/CdS S-scheme nanocomposites

BiFeO3 (BFO), as a kind of narrow band-gap semiconductor material, has gradually emerged advantages in the application of photocatalysis. In this paper, Ca doped BFO nanoparticles Bi0.9Ca0.1FeO3 (BCFO) were prepared by sol-gel method. And BCFO and CdS nanocomposites with two morphologies were obtained by controlling the time of loading CdS under a low temperature liquid phase process. It is found that the band gap becomes narrower after doping Ca into BFO, which is conducive to the absorption of visible light. Among all the samples, the composite of CdS nanowires and BCFO nanoparticles obtained by reaction time of 10 min has the best photocatalytic performance. The degradation rate of Methyl Orange solution was 94% after 90 min under visible light irradiation, which was much higher than that of pure BCFO and CdS. Furthermore, significant enhancement in the degradation rate (100% degradation in 60 min) can be achieved in poled samples after electric polarization process. The highest degradation rate is due to the promoted separation of photogenerated carriers induced by the internal polarization field and the formation of S-scheme heterostructure between BCFO and CdS. Such BCFO-CdS nanocomposites may bring new insights into designing highly efficient photocatalyst.

Four Discrete Silver Iodobismuthates/Bromobismuthates with Metal Complexes: Syntheses, Structures, Photocurrent Responses, and Theoretical Studies.

Using in situ formed metal complexes of [Fe(bipy)3]2+ or [Ni(bipy)3]2+ (bipy = 2,2'-bipyridine) as templates, four new Ag-Bi-X (X = I and Br) compounds are first isolated in the metal-complex-decorated heterometallic halobismuthate family, namely [M(bipy)3]AgBiI6 (M = Fe (1), Ni (2)), [Fe(bipy)3]AgBiBr6 (3), and [Ni(bipy)3]AgBiBr6 (4). Compounds 1-4 feature discrete [AgBiX6]n2n- anions, exhibiting three polymorphisms that may be ascribed to the different stackings and the flexible condensations of [BiX6] octahedrons and [AgX4] tetrahedra/[AgX3] triangles. UV-vis diffuse reflectance analyses reveal that they are narrow band gap semiconductor materials (ca. 1.82-2.13 eV). Intriguingly, the title compounds display excellent photoelectrical switching properties, with photocurrent density following the order 3 > 4 > 2 > 1. In addition, the comparative studies of intermolecular interactions, theoretical band structures, density of states, and effective masses of three polymorphisms have also been investigated.

Gate-controlled supercurrent in ballistic InSb nanoflag Josephson junctions

High-quality III–V narrow bandgap semiconductor materials with strong spin–orbit coupling and large Landé g-factor provide a promising platform for next-generation applications in the field of high-speed electronics, spintronics, and quantum computing. Indium antimonide (InSb) offers a narrow bandgap, high carrier mobility, and small effective mass and, thus, is very appealing in this context. In fact, this material has attracted tremendous attention in recent years for the implementation of topological superconducting states supporting Majorana zero modes. However, high-quality heteroepitaxial two-dimensional (2D) InSb layers are very difficult to realize owing to the large lattice mismatch with all commonly available semiconductor substrates. An alternative pathway is the growth of free-standing single-crystalline 2D InSb nanostructures, the so-called nanoflags. Here, we demonstrate fabrication of ballistic Josephson-junction devices based on InSb nanoflags with Ti/Nb contacts that show a gate-tunable proximity-induced supercurrent up to 50 nA at 250 mK and a sizable excess current. The devices show clear signatures of subharmonic gap structures, indicating phase-coherent transport in the junction and a high transparency of the interfaces. This places InSb nanoflags in the spotlight as a versatile and convenient 2D platform for advanced quantum technologies.

A Review on Thermophotovoltaic Cell and Its Applications in Energy Conversion: Issues and Recommendations.

Generally, waste heat is redundantly released into the surrounding by anthropogenic activities without strategized planning. Consequently, urban heat islands and global warming chronically increases over time. Thermophotovoltaic (TPV) systems can be potentially deployed to harvest waste heat and recuperate energy to tackle this global issue with supplementary generation of electrical energy. This paper presents a critical review on two dominant types of semiconductor materials, namely gallium antimonide (GaSb) and indium gallium arsenide (InGaAs), as the potential candidates for TPV cells. The advantages and drawbacks of non-epitaxy and epitaxy growth methods are well-discussed based on different semiconductor materials. In addition, this paper critically examines and summarizes the electrical cell performance of TPV cells made of GaSb, InGaAs and other narrow bandgap semiconductor materials. The cell conversion efficiency improvement in terms of structural design and architectural optimization are also comprehensively analyzed and discussed. Lastly, the practical applications, current issues and challenges of TPV cells are critically reviewed and concluded with recommendations for future research. The highlighted insights of this review will contribute to the increase in effort towards development of future TPV systems with improved cell conversion efficiency.

Conversion efficiency of resonant cavity enhanced narrow bandgap interband cascade photovoltaic cells

By combining an interband cascade (IC) configuration with an optical cavity, a novel approach to achieve efficient narrow bandgap photovoltaic (PV) cells is proposed. The proposed resonant cavity enhanced (RCE) ICPV cells can significantly alleviate the challenging issues in narrow bandgap semiconductor materials, which include a small absorption coefficient, a short diffusion length, and a high dark current density. Through simulations with realistic material parameters based on InAs/GaSb superlattice heterostructures, RCE ICPV cells are capable of achieving a conversion efficiency that exceeds 60%, which is much higher than what can be achieved with any other approach, especially with materials of a bandgap smaller than 0.3 eV. By varying structure parameters such as the absorber thickness, number of cascade stages, and the top mirror reflectance, we demonstrate how an RCE ICPV cell can be constructed to achieve an optimized device performance with high conversion efficiency. Also, a design example of a practical RCE narrow bandgap ICPV cell is provided.

Investigation of Cylindrical Channel Gate All Around InGaAs/InP Heterojunction Heterodielectric Tunnel FETs

This paper investigated the design and TCAD simulation of heterojunction Tunnel Field Effect Transistor (TFET) with dual gate material. The proposed device structure is designed with narrow bandgap semiconductor material InGaAs (0.74 eV) at source region and wider energy bandgap InP (1.34 eV) at channel and drain regions. The narrow bandgap at source/channel junction improves the tunneling generation rate and the wider bandgap at drain/channel junction reduces the ambipolar behavior. In addition to heterojunction, the dual work function at gate Metal (M1) and Metal (M2) and HfO2/SiO2 stacked dielectric helps to improve the band-gap narrowing as well as reduced leakage current. The proposed device electrical parameters such as Surface potential, energy band diagram, electric field, transconductance and drain current has been analyzed. The simulation results show significant improvement in ON current (10−5A/μm) and reduced OFF current (10−12A/μm) in the proposed device structure. The presented result reveals that the InGaAs/InP heterojunction stacked dielectric TFET is a good candidate for low power applications.

Infrared photovoltaic detector based on p-GeTe/n-Si heterojunction

GeTe is an important narrow bandgap semiconductor material and has found application in the fields of phase change storage as well as spintronics devices. However, it has not been studied for application in the field of infrared photovoltaic detectors working at room temperature. Herein, GeTe nanofilms were grown by magnetron sputtering technique and characterized to investigate its physical, electrical, and optical properties. A high-performance infrared photovoltaic detector based on GeTe/Si heterojunction with the detectivity of 8 × 1011 Jones at 850 nm light irradiation at room temperature was demonstrated.

Infrared photodetector based on GeTe nanofilms with high performance.

GeTe is an important narrow band gap semiconductor material, which has found application in the fields of thermoelectricity, phase change storage as well as switch. However, it has not been studied for application in the field of photodetectors. Here, GeTe thin films were grown by magnetron sputtering and their material structure, optical and electrical properties were compared before and after annealing. High-performance photodetectors with detectivity of ${\sim}{{10}^{13}}$∼1013 Jones at 850 nm light were demonstrated. Thus the novel, to the best of our knowledge, application of GeTe in optoelectronic devices is reported in this work.