Search Results (72)

Intermediate-band photovoltaics promise single-junction efficiencies that exceed the Shockley and Queisser limit, yet viable material platforms and device geometries remain under debate. Here, we perform comprehensive two-dimensional device-scale simulations using Silvaco Atlas TCAD to analyze p-i-n In_0.20Ga_0.80N solar cells in which the intermediate band is supplied by In_0.35Ga_0.65N quantum dots located inside the intrinsic layer. Quantum-dot diameters from 1 nm to 10 nm and areal densities up to 116 dots per period are evaluated under AM 1.5G, one-sun illumination at 300 K. The baseline pn junction achieves a simulated power-conversion efficiency of 33.9%. The incorporation of a single 1 nm quantum-dot layer dramatically increases efficiency to 48.1%, driven by a 35% enhancement in short-circuit current density while maintaining open-circuit voltage stability. Further increases in dot density continue to boost current but with diminishing benefit; the highest efficiency recorded, 49.4% at 116 dots, is only 1.4 percentage points above the 40-dot configuration. The improvements originate from two-step sub-band-gap absorption mediated by the quantum dots and from enhanced carrier collection in a widened depletion region. These results define a practical design window centred on approximately 1 nm dots and about 40 dots per period, balancing substantial efficiency gains with manageable structural complexity and providing concrete targets for epitaxial implementation. Full article

III-Nitride semiconductors (BN, AlN, GaN, and InN) exhibit exceptional electronic and mechanical properties that render them indispensable for high-performance optoelectronic, power, and high-frequency device applications. This study implements first-principles Density Functional Theory (DFT) calculations to elucidate the influence of hydrostatic pressure on the electronic, elastic, and mechanical properties of these materials in the wurtzite crystallographic configuration. Our computational analysis demonstrates that the bandgap energy exhibits a positive pressure coefficient for GaN, AlN, and InN, while BN manifests a negative pressure coefficient consistent with its indirect-bandgap characteristics. The elastic constants and derived mechanical properties reveal material-specific responses to applied pressure, with BN maintaining superior stiffness across the pressure range investigated, while InN exhibits the highest ductility among the studied compounds. GaN and AlN demonstrate intermediate mechanical robustness, positioning them as optimal candidates for pressure-sensitive applications. Furthermore, the observed nonlinear trends in elastic moduli under pressure reveal anisotropic mechanical responses during compression, a phenomenon critical for the rational design of strain-engineered devices. The computational results provide quantitative insights into the pressure-dependent behavior of III-N semiconductors, facilitating their strategic implementation and optimization for high-performance applications in extreme environmental conditions, including high-power electronics, deep-space exploration systems, and high-pressure optoelectronic devices. Full article

This investigation is centered on the analysis of frequency response characteristics of a p-i-n photodiode using InxGa_1−xAs/InP. The InGaAs/InP can be developed under three conditions: compression, tensile strain, and lattice matching. Initially, we performed calculations on strain, bandgap energy (E_g), and absorption coefficient. We then optimized the influence of indium concentration (x) on stability, critical thickness, bandgap energy, and absorption coefficient. The effects of temperature and deformation on E_g were also studied. Finally, we optimized the cutoff frequency (f_c), capacitive effects, and response frequency by considering the impact of x, active layer thickness (d), and surface area (S). For our future endeavors, we intend to explore additional parameters that may affect the p-i-n response. In future work, we can add transparent double layers in the i. InGaAs layer to reduce the transit time, leading to the development of an ultrafast photodiode. Full article

The development of metal–organic framework (MOF)-based composites for photocatalytic hydrogen evolution has garnered significant attention due to their tunable structures, high surface area, and abundant active sites. Recent advancements focus on enhancing light absorption, charge separation, and catalytic efficiency through strategies such as ligand functionalization, metal doping, heterojunction formation, and plasmonic coupling effects. For instance, modifications with Ir (III) complexes and Pt nanoparticles have significantly improved hydrogen evolution rates, while sandwich-structured MOF composites demonstrate optimized charge separation through tailored micro-environments and proton reduction efficiency. Additionally, integrating MOFs with semiconductors (e.g., CdS, g-C₃N₄) or plasmonic metals (e.g., Au) enhances visible-light responsiveness and stability. This review highlights key design principles, performance metrics, and mechanistic insights, providing a roadmap for future research in MOF-based photocatalysts for sustainable hydrogen production. Challenges such as long-term stability and scalable synthesis are also discussed to guide further innovations in this field. Full article

To address the challenges of environmental adaptability and passivation in nanoscale zero-valent iron (nFe⁰) systems, we developed oxalate-modified nFe⁰ (nFe_oxa) through a coordination-driven synthesis strategy, aiming to achieve high-efficiency Cr(VI) removal with improved stability and reusability. Structural characterization (STEM and FT-IR) confirmed the formation of a FeC₂O₄/nFe⁰ heterostructure, where oxalate coordinated with Fe(II) to construct a semiconductor interface that effectively inhibits anoxic passivation while enabling continuous electron supply, achieving 100% Cr(VI) removal efficiency within 20 min at an optimal oxalate/Fe molar ratio of 1/29. Mechanistic studies revealed that the oxalate ligand accelerates electron transfer from the Fe⁰ core to the surface via the FeC₂O₄-mediated pathway, as evidenced by EIS and LSV test analyses. This process dynamically regenerates surface Fe(II) active sites rather than relying on static-free Fe(II) adsorption. XPS and STEM further demonstrated that Cr(VI) was reduced to Cr(III) and uniformly co-precipitated with Fe(II/III)-oxalate complexes, effectively immobilizing chromium. The synergy between the protective semiconductor layer and the ligand-enhanced electron transfer endows nFe_oxa with superior reactivity. This work provides a ligand-engineering strategy to design robust nFe⁰-based materials for sustainable remediation of metal oxyanion-contaminated water. Full article

In the context of increasing digitalization and the emergence of applications such as smart cities, embedded devices are becoming ever more pervasive, mobile, and ubiquitous. Due to increasing concerns around energy efficiency, gate density, and scalability in the semiconductor industry, there has been much interest recently in the fabrication of viable low-power energy-efficient devices. The Hetero-Dielectric Gate-All-Around (HD-GAA) MOSFET represents a cutting-edge transistor architecture designed for superior sustainability and energy efficiency, improving the overall efficiency of the system by reducing leakage and enhancing gate control; therefore, as part of the transition to a sustainable future, several semiconductor industries, including Intel, Samsung, Texas Instruments, and IBM, are using this technology. In this study, Hetero-Dielectric Single-Metal Gate-All-Around MOSFET (HD-SM-GAA MOSFET) devices and circuits were designed using Schottky source/drain contacts and tunable high-k dielectric Hf_xTi_1−xO₂ in the TCAD simulator using the following specifications: N-Channel HD-SM-GAA MOSFET (‘Device-I’) with a 5 nm radius and a 21 nm channel length alongside two P-Channel HD-SM-GAA MOSFETs (‘Device-II’ and ‘Device-III’) with radii of 5 nm and 8 nm, respectively, maintaining the same channel length. Thereafter, the inverters were implemented using these devices in the COGENDA TCAD simulator. The results demonstrated significant reductions in short-channel effects: subthreshold swing (SS) (‘Device-I’ = 61.5 mV/dec, ‘Device-II’ = 61.8 mV/dec) and drain-induced barrier lowering (DIBL) (‘Device-I’ = 8.2 mV/V, ‘Device-II’ = 8.0 mV/V) in comparison to the existing literature. Furthermore, the optimized inverters demonstrated significant improvements in noise margin values such as Noise Margin High (NM_H) and Noise Margin Low (NM_L), with Inverter-1 showing 38% and 44% enhancements and Inverter-2 showing 40% and 37% enhancements, respectively, compared to the existing literature. The results achieved illustrate the potential of using this technology (e.g., for power inverters) in embedded power control applications where energy efficiency and scalability are important, such as sustainable smart cities. Full article

The increasing penetration of renewable energy sources (RESs) into medium-voltage (MV) and low-voltage (LV) power systems presents significant challenges in ensuring power grid stability and energy sustainability. Advanced power conversion technologies are essential to mitigate voltage and frequency fluctuations while meeting stringent power quality standards. RES-based generation systems typically employ multistage power electronics to achieve: (i) maximum power point tracking; (ii) galvanic isolation and voltage transformation; (iii) high-quality power injection into the power grid. In this context, this paper provides a comprehensive review of up-to-date isolated DC–DC converter topologies tailored for the integration of RES. As a contribution to support this topic, recent advancements in solid-state transformers (SSTs) are explored, with particular emphasis on the adoption of wide bandgap (WBG) semiconductors technologies, such as silicon carbide (SiC) and gallium nitride (GaN). These devices have revolutionized modern power systems by enabling operation at a higher switching frequency, enhanced efficiency, and increased power density. By consolidating state-of-the-art advancements and identifying technical challenges, this review offers insights into the suitability of power converter topologies in light of future trends, serving as a valuable resource for optimizing grid-connected RES-based sustainable power systems. Full article

Eskebornite (CuFeSe₂) is a I–III–VI₂ semiconductor with a tetragonal crystal structure, known for its intriguing electrical and magnetic properties. However, experimental studies on this material remain scarce. In this study, Ni-doped eskebornite, Cu_1−xNi_xFeSe₂ (x = 0.02–0.06), was synthesized via solid-state methods by substituting Ni²⁺ for Cu⁺. Mechanical alloying was employed to prepare the compounds, followed by hot pressing. X-ray diffraction analysis revealed the eskebornite phase alongside a minor secondary phase, identified as penroseite (NiSe₂) with a cubic crystal structure. Thermoelectric properties were measured over the temperature range of 323–623 K. The Seebeck coefficient exhibited p-type behavior at low temperatures but transitioned to n-type at higher temperatures, indicating a temperature-dependent p–n transition due to changes in the dominant charge carriers. With increasing Ni doping, the Seebeck coefficient increased positively at low temperatures and negatively at high temperatures, with the p–n transition temperature shifting to lower values. Electrical conductivity decreased with higher Ni doping levels, while its positive temperature dependence became more pronounced, reflecting non-degenerate semiconductor behavior. Thermal conductivity showed a negative temperature dependence but increased with higher Ni content. The highest thermoelectric performance was observed for Cu_0.98Ni_0.02FeSe₂, achieving ZT_p = 0.30 × 10^–3 at 523 K, and for Cu_0.94Ni_0.06FeSe₂, achieving ZT_n = 0.55 × 10^–3 at 623 K, where ZT_p and ZT_n represent the dimensionless figure of merit for p-type and n-type thermoelectric materials, respectively. Full article

Direct wide-bandgap III-Ns and II-Os have recently gained considerable attention due to their unique electrical and chemical properties. These novel semiconductors are being explored to design short-wavelength light-emitting diodes, sensors/biosensors, photodetectors for integration into flexible transparent nanoelectronics/photonics to achieve high-power radio-frequency modules, and heat-resistant optical switches for communication networks. Knowledge of the elastic constants structural and mechanical properties has played crucial roles both in the basic understanding and assessing materials’ use in thermal management applications. In the absence of experimental structural, elastic constants, and mechanical traits, many theoretical simulations have yielded inconsistent results. This work aims to investigate the basic characteristics of tetrahedrally coordinated, partially ionic BeO, MgO, ZnO, and CdO, and partially covalent BN, AlN, GaN, and InN materials. By incorporating a bond-orbital and a valance force field model, we have reported comparative results of our systematic calculations for the bond length $\mathrm{d}$, bond polarity ${\mathsf{\alpha }}_{\mathrm{P}}$, covalency ${\mathsf{\alpha }}_{\mathrm{C}}$, bulk modulus $\mathrm{B}$, elastic stiffness $\mathrm{C}(={\displaystyle \frac{\left[{\mathrm{c}}_{11}-{\mathrm{c}}_{12}\right]}{2}})$, bond-stretching $\mathsf{\alpha }$ and bond-bending $\mathsf{\beta }$ force constants, Kleinmann’s internal displacement ζ, and Born’s transverse effective charge ${\mathrm{e}}_{\mathrm{T}}^{*}$. Correlations between $\mathrm{C}/\mathrm{B}$, $\mathsf{\beta }$/$\mathsf{\alpha }$, ${\displaystyle \frac{{\mathrm{c}}_{12}}{{\mathrm{c}}_{11}}},$ ζ, $\mathrm{a}\mathrm{n}\mathrm{d}$ ${\mathsf{\alpha }}_{\mathrm{C}}$revealed valuable trends of structural, elastic, and bonding characteristics. The study noticed AlN and GaN (MgO and ZnO) showing nearly comparable features, while BN (BeO) is much harder compared to InN (CdO) material, with drastically softer bonding. Calculations of microhardness $\mathrm{H}$, shear modulus $\mathrm{G},$ and Young’s modulus $\mathrm{Y}$ have predicted BN (BeO) satisfying a criterion of super hardness. III-Ns (II-Os) could be vital in electronics, aerospace, defense, nuclear reactors, and automotive industries, providing integrity and performance at high temperature in high-power applications, ranging from heat sinks to electronic substrates to insulators in high-power devices. Full article

The advent of two-dimensional (2D) ferroelectrics offers a new paradigm for device miniaturization and multifunctionality. Recently, 2D α-In₂Se₃ and related III–VI compound ferroelectrics manifest room-temperature ferroelectricity and exhibit reversible spontaneous polarization even at the monolayer limit. Here, we employ first-principles calculations to investigate group-III selenide van der Waals (vdW) heterojunctions built up by 2D α-In₂Se₃ and α-Ga₂Se₃ ferroelectric (FE) semiconductors, including structural stability, electrostatic potential, interfacial charge transfer, and electronic band structures. When the FE polarization directions of α-In₂Se₃ and α-Ga₂Se₃ are parallel, both the α-In₂Se₃/α-Ga₂Se₃ P↑↑ (UU) and α-In₂Se₃/α-Ga₂Se₃ P↓↓ (NN) configurations possess strong built-in electric fields and hence induce electron–hole separation, resulting in carrier depletion at the α-In₂Se₃/α-Ga₂Se₃ heterointerfaces. Conversely, when they are antiparallel, the α-In₂Se₃/α-Ga₂Se₃ P↓↑ (NU) and α-In₂Se₃/α-Ga₂Se₃ P↑↓ (UN) configurations demonstrate the switchable electron and hole accumulation at the 2D ferroelectric interfaces, respectively. The nonvolatile characteristic of ferroelectric polarization presents an innovative approach to achieving tunable n-type and p-type conductive channels for ferroelectric field-effect transistors (FeFETs). In addition, in-plane biaxial strain modulation has successfully modulated the band alignments of the α-In₂Se₃/α-Ga₂Se₃ ferroelectric heterostructures, inducing a type III–II–III transition in UU and NN, and a type I–II–I transition in UN and NU, respectively. Our findings highlight the great potential of 2D group-III selenides and ferroelectric vdW heterostructures to harness nonvolatile spontaneous polarization for next-generation electronics, nonvolatile optoelectronic memories, sensors, and neuromorphic computing. Full article

Due to the excellent quantum conversion and spectral response characteristics of the AlGaN photocathode, it has become the most promising III-V group semiconductor photocathode in solar-blind signal photoconversion devices in the ultraviolet band. Herein, the influence factors of the time-resolved characteristics of the AlGaN photocathode are researched by solving the photoelectron continuity equation and photoelectron flow density equation, such as the AlN/AlGaN interface recombination rate, AlGaN electron diffusion coefficient, and AlGaN activation layer thickness. The results show that the response time of the AlGaN photocathode decreases gradually with the increase in AlGaN photoelectron diffusion coefficient and AlN/AlGaN interface recombination rate, but the response time of the AlGaN photocathode gradually becomes saturated with the further increase in AlN/AlGaN interface recombination rate. When the thickness of the AlGaN photocathode is reduced from 250 nm to 50 nm, the response time of the AlGaN photocathode decreases from 63.28 ps to 9.91 ps, and the response time of AlGaN photocathode greatly improves. This study provides theoretical guidance for the development of a fast response UV detector. Full article

A gallium nitride (GaN) semiconductor is one of the most promising materials integrated into biomedical devices to play the roles of connecting, monitoring, and manipulating the activity of biological components, due to its excellent photoelectric properties, chemical stability, and biocompatibility. In this work, it was found that the photogenerated free charge carriers of the GaN substrate, as an exogenous stimulus, served to promote neural stem cells (NSCs) to differentiate into neurons. This was observed through the systematic investigation of the effect of the persistent photoconductivity (PPC) of GaN on the differentiation of primary NSCs from the embryonic rat cerebral cortex. NSCs were directly cultured on the GaN surface with and without ultraviolet (UV) irradiation, with a control sample consisting of tissue culture polystyrene (TCPS) in the presence of fetal bovine serum (FBS) medium. Through optical microscopy, the morphology showed a greater number of neurons with the branching structures of axons and dendrites on GaN with UV irradiation. The immunocytochemical results demonstrated that GaN with UV irradiation could promote the NSCs to differentiate into neurons. Western blot analysis showed that GaN with UV irradiation significantly upregulated the expression of two neuron-related markers, βIII-tubulin (Tuj-1) and microtubule-associated protein 2 (MAP-2), suggesting that neurite formation and the proliferation of NSCs during differentiation were enhanced by GaN with UV irradiation. Finally, the results of the Kelvin probe force microscope (KPFM) experiments showed that the NSCs cultured on GaN with UV irradiation displayed about 50 mV higher potential than those cultured on GaN without irradiation. The increase in cell membrane potential may have been due to the larger number of photogenerated free charges on the GaN surface with UV irradiation. These results could benefit topical research and the application of GaN as a biomedical material integrated into neural interface systems or other bioelectronic devices. Full article

This work reports on the possibility of sustaining a stable operation of polarization-doped InGaN light emitters over a particularly broad temperature range. We obtained efficient emission from InGaN light-emitting diodes between 20 K and 295 K and from laser diodes between 77 K and 295 K under continuous wave operation. The main part of the p-type layers was fabricated from composition-graded AlGaN. To optimize injection efficiency and improve contact resistance, we introduced thin Mg-doped layers of GaN (subcontact) and AlGaN (electron blocking layer in the case of laser diodes). In the case of LEDs, the optical emission efficiency at low temperatures seems to be limited by electron overshooting through the quantum wells. For laser diodes, a limiting factor is the freeze-out of the magnesium-doped electron blocking layer for temperatures below 160 K. The GaN:Mg subcontact layer works satisfyingly even at the lowest operating temperature (20 K). Full article

Gallium nitride (GaN) semiconductors and their broadband InGaN alloys in their hexagonal phase have been extensively studied over the past 30 years and have allowed the development of blue-ray lasers, which are essential disruptive developments. In addition to high-efficiency white light-emitting diodes, which have revolutionized lighting technologies and generated a great industry around these semiconductors, several transistors have been developed that take advantage of the characteristics of these semiconductors. These include power transistors for high-frequency applications and high-power transistors for power electronics, among other devices, which have far superior achievements. However, less effort has been devoted to studying GaN and InGaN alloys grown in the cubic phase. The metastable or cubic phase of III-N alloys has superior characteristics compared to the hexagonal phase, mainly because of the excellent symmetry. It can be used to improve lighting technologies and develop other devices. Indium gallium nitride, In_xGa_1−xN alloy, has a variable band interval of 0.7 to 3.4 eV that covers almost the entire solar spectrum, making it a suitable material for increasing the efficiencies of photovoltaic devices. In this study, we successfully synthesized high-quality cubic InGaN films on MgO (100) substrates using plasma-assisted molecular beam epitaxy (PAMBE), demonstrating tunable emissions across the visible spectrum by varying the indium concentration. We significantly reduced the defect density and enhanced the crystalline quality by using an intermediate cubic GaN buffer layer. We not only developed a heterostructure with four GaN/InGaN/GaN quantum wells, achieving violet, blue, yellow, and red emissions, but also highlighted the immense potential of cubic InGaN films for high-efficiency light-emitting diodes and photovoltaic devices. Achieving better p-type doping levels is crucial for realizing diodes with excellent performance, and our findings will pave the way for this advancement. Full article

Using the example of III–V nitrides crystallizing in a wurtzite structure (GaN, AlN, and InN), this review presents the special role of hydrostatic pressure in studying semiconductor properties. Starting with a brief description of high-pressure techniques for growing bulk crystals of nitride compounds, we focus on the use of hydrostatic pressure techniques in both experimental and theoretical investigations of the special properties of nitride compounds, their alloys, and quantum structures. The bandgap pressure coefficient is one of the most important parameters in semiconductor physics. Trends in its behavior in nitride structures, together with trends in pressure-induced phase transitions, are discussed in the context of the behavior of other typical semiconductors. Using InN as an example, the pressure-dependent effects typical of very narrow bandgap materials, such as conduction band filling or effective mass behavior, are described. Interesting aspects of bandgap bowing in In-containing nitride alloys, including pressure and clustering effects, are discussed. Hydrostatic pressure also plays an important role in the study of native defects and impurities, as illustrated by the example of nitride compounds and their quantum structures. Experiments and theoretical studies on this topic are reviewed. Special attention is given to hydrostatic pressure and strain effects in short periods of nitride superlattices. The explanation of the discrepancies between theory and experiment in optical emission and its pressure dependence from InN/GaN superlattices led to the well-documented conclusion that InN growth on the GaN substrate is not possible. The built-in electric field present in InGaN/GaN and AlGaN/GaN heterostructures crystallizing in a wurtzite lattice can reach several MV/cm, leading to drastic changes in the physical properties of these structures and related devices. It is shown how hydrostatic pressure modifies these effects and helps to understand their origin. Full article