This work presents a comprehensive DC and AC performance analysis of AlN buffered AlGaN/GaN HEMTs without (w/o) and with an AlN spacer using TCAD simulations. The incorporation of the AlN spacer substantially enhances the HEMT performance through improved polarization induced charge confinement in the channel. The spacer HEMT demonstrates an increased drain current (Ids) of 391 mA/mm as relative to 321 mA/mm in the typical device i.e., w/o a spacer HEMT. Furthermore, the introduction of the AlN spacer improves the transconductance from 121 mS/mm for the conventional HEMT without an AlN spacer to 147 mS/mm for the spacer engineered HEMT. A substantial reduction in the OFF-state leakage current from 9.05 × 10–7 2.87 × 10–7 A/mm which leads to nearly one order of magnitude enhancement in the Ion/Ioff current ratio. The breakdown voltage is also enhanced significantly from 586 to 813 V that indicates the superior high voltage capability of a spacer HEMT. In the AC domain, the reduction in gate capacitances including Cgs, Cgd, and Cgg contributes to an improved cut-off frequency (ft) from 1.17 to 1.42 GHz. The observed improvements are primarily attributed to enhanced polarization effects, increased two-dimensional electron gas (2DEG) density, and a reduced parasitic effect because of the AlN spacer. These results highlight the effectiveness of AlN spacer engineering in advancing high RF/frequency and power GaN based HEMT devices.
A TCAD-based comparative study of AlGaN, InAlN, and quaternary InAlGaN barrier GaN HEMTs integrated with an InGaN back-barrier and β-Ga2O3 buffer layer on a SiC substrate is presented. The influence of barrier composition on carrier confinement, electrostatic behavior, and high-frequency characteristics is systematically investigated. The quaternary In0.10Al0.20Ga0.70N barrier device exhibits improved polarization-induced carrier confinement and enhanced 2DEG density of 6.38 ×10^13 cm–2. Owing to the optimized band alignment and reduced carrier spillover, the device achieves a maximum drain current of 2.15 A/mm, peak gm of 330 mS/mm, and fT of 530 GHz. In addition, lower intrinsic capacitances of 0.356 pF/mm for C_GS and 0.112 pF/mm for C_GD are obtained, leading to improved RF switching characteristics. The proposed structure also demonstrates excellent OFF-state behavior with leakage current in the order of 10–15 A/mm and a breakdown voltage of 67 V. The obtained results indicate that quaternary barrier and back-barrier engineering provide an effective pathway for next-generation microwave and power electronic systems.
This study presents a comprehensive density functional theory examination of Li2NaSb and RuTaSb Heusler alloys, exploring structural, elastic, thermodynamic, and phonon dispersion properties. Quantum ESPRESSO and Thermo_pw calculations reveal optimized lattice constants of 6.8603 Å and 6.1608 Å for Li2NaSb and RuTaSb, respectively. Poisson’s ratio values of 0.16 for Li2NaSb and 0.32 for RuTaSb indicate that the materials exhibit brittleness and ductility, respectively. Anisotropic values 2.29 and 1.04 for Li2NaSb and RuTaSb, respectively, confirm material directionality. Thermodynamic analysis reveals an increase in vibrational energy, a decrease in free energy, and an increase in entropy as temperature increases. Phonon dispersion calculations demonstrate the materials' dynamic stability. The results obtained for Li2NaSb and RuTaSb have not been reported in any literature.
This study presents a numerical analysis of methods to enhance light absorption in P3HT : PCBM organic solar cells by adding trimetallic Ag : Au : Cu nanoparticles to the active layer. Finite-difference time-domain simulations in Lumerical, under standard illumination conditions, are used to compare the optical performance of organic solar cells (OSCs) containing trimetallic nanoparticles with those doped with monometallic Ag, Au, and Cu nanoparticles. The analysis focuses on wavelength-dependent absorbance, scattering, and absorption cross-sections, as well as near-field electric-field intensity distributions for nanoparticles with an average size of 10 nm. The results show that trimetallic Ag : Au : Cu nanoparticles exhibit superior spectral absorption and more concentrated electromagnetic fields than their single-metal counterparts. Doping with Ag : Au : Cu nanoparticles results in an average absorption enhancement of approximately 3–5
In this study, the electrical properties, photoluminescence spectra and the low-frequency noise behaviors of the polar, semipolar, and nonpolar AlGaN-based UV LEDs grown on the sapphire substrate have been measured and investigated at room temperature. The electrical parameters (such as threshold voltage Vth, reverse saturate current Is, series resistor Rs and ideality factor n), photoluminescence spectra (peak wavelength, FWHM) and the low-frequency noise parameters (white noise amplitude A, 1/f noise amplitude B, the frequency exponent of 1/f noise γ, the amplitude of g-r noise C, the corner frequency of g-r noise f0 and the frequency exponent factor α) of the examined UV LEDs have been fitted and extracted using the classical LED current-voltage equation and low-frequency noise equation. In addition, we studied the relationships between the parameters of low-frequency noise, γ, f0, α and the current during the LED turn-on process. The conclusion shows that the electrical properties, peak wavelength of photoluminescence and low-frequency noise parameters of the three studied AlGaN-based UV LEDs show a strong polarity-dependence under the operation process. The quantum-confined Stark effect induced by the built-in electric field, strength of the polarization field and the defect density in the active region play the major factors affecting the electrical properties, luminescence properties and low-frequency noise behaviors of AlGaN-based UV LEDs.
The structural and elastic characteristics of LaPtGe3 were reported using density functional theory (DFT) implemented in the CASTEP code. The study reveals significant pressure-induced effects of external pressure on these properties. The lattice parameter c changes more than a and b under pressure, highlighting the anisotropic nature of LaPtGe3. The reduction in unit cell volume under pressure mainly arises from shifts in the positions of Ge and Pt atoms. As pressure increased, bond lengths decreased, with the most pronounced reduction shows in Ge-Ge bonds. This contraction in bond lengths contributed to the decrease in unit cell volume and influenced other related properties of the material. The calculated elastic constants of LaPtGe3 at both ambient conditions and under external pressure adhered to the Born–Huang stability criteria, confirming the material’s mechanical stability. With increasing pressure, the bulk modulus of LaPtGe3 rose, indicating that the material became harder. Additionally, Pugh’s ratio, which exceeded 1.75, suggested a ductile nature, and this ductility further increased with applied pressure. This behavior was corroborated by Poisson’s ratio, which also indicated enhanced ductility under higher pressure. An analysis of the anisotropy factor revealed that LaPtGe3 remained elastically anisotropic across the applied pressure range of 0 to 25 GPa, as the factor remained below unity. A strong anomaly was indicates at approximately 15 GPa in several properties, including shear modulus, Young’s modulus, Pugh’s ratio, Poisson’s ratio, and the universal anisotropic factor. This anomaly is likely associated with a structural phase transition in LaPtGe3, marking a significant change in its mechanical and elastic behavior under high-pressure conditions.
Abstract – The dielectric properties of Tl-doped ε-GaSe (ε-GaSe〈Tl〉) single crystals in alternating electric fields were investigated. The frequency dispersion of the complex dielectric permittivity was analyzed using the Havriliak–Negami (HN) formalism in combination with the complex dielectric modulus approach. The main dielectric relaxation parameters, including the characteristic relaxation time, spectral width and asymmetry, as well as the high-frequency dielectric permittivity, were determined. It is shown that the combined use of HN analysis and the modulus formalism enables a reliable evaluation of the defect lifetime distribution even in the presence of a significant contribution of electrical conductivity to the dielectric response of ε-GaSe〈Tl〉.
Accurate noise prediction is essential for reliable high-frequency semiconductor device design. This work presents an integrated analytical framework for evaluating thermal noise in a ferroelectric (Fe)-doped, dual-metal-gate (DMG) AlN/AlGaN/GaN HEMT, based on the Cappy noise model and explicitly accounting for the influence of gate length on transconductance. Closed-form expressions are derived for the minimum noise factor (Fmin), noise conductance (Gn), output noise, and integrated noise, and are evaluated for device parameters Tox = 4.5 nm, L1 = 200 nm and L2 = 300 nm. The dual-gate architecture is shown to suppress thermal noise more effectively than a single virtual-gate (SVG) design because the split work-function gates strengthen electrostatic control of the channel and raise transconductance, which in turn lowers both the output and integrated noise. At Cg1 = 4 mF and Cg2 = 4.41 mF, the intersection of the integrated-noise and transconductance curves occurs at (2.3974, 2.4701 dB), compared with (2.4107, 2.4914 dB) for the conventional output-noise formulation, an improvement of about 27
This work demonstrates a charge plasma-based Gate-All-Around (GAA) nanowire field-effect transistor (FET) for high-sensitivity ammonia (NH3) gas sensing. The proposed device utilizes palladium (Pd) and molybdenum (Mo) as gate metals, where Pd exhibits superior performance due to its strong catalytic interaction with NH3 molecules. The sensing mechanism is governed by adsorption-induced work function modulation at the metal-gate interface, leading to measurable changes in threshold voltage (Vth), ON-state current (ION), and OFF-state current (IOFF). A systematic work function variation from 50 to 200 meV reveals significant enhancement in sensing metrics, with the ION/IOFF ratio improving from 2.6 × 108 to 1.6 × 1011 for Pd. Furthermore, channel length scaling and dielectric engineering demonstrate improved electrostatic control, with HfO2 ( 6.3
The threshold voltage model for an ultra-thin nano-sheet junctionless field-effect transistor (UT-NS JLFET) is provided analytically in this paper. Solving the three-dimensional Poisson’s equation under full depletion conditions gives the surface potential of the cuboidal gate arrangement. To simplify the analysis, the 3-D problem is divided into two symmetric double-gate configurations in the x–z and y–z planes. The overall threshold voltage is calculated using a perimeter-weighted summation of individual threshold voltages along the channel width (w2) and thickness (w1). The model includes quantum mechanical corrections to account for quantum confinement in ultra-thin channels. A detailed analysis is carried out to determine how essential device variables such as oxide thickness, channel length, and channel doping concentration influence the threshold voltage. Furthermore, to evaluate device behavior, the subthreshold characteristics and drain current performance of nano-sheet JLFETs are compared to those of nanowire JLFETs. The recommended analytical results support the accuracy and usefulness of the constructed model for nanoscale junctionless devices, which show strong agreement with ATLASTM TCAD simulation data.
The ternary chalcopyrite semiconductors CuMX2 (M = Ga, In; X = S, Se, Te) have attracted considerable attention due to their promising applications in optoelectronic and thermoelectric devices. In the present work, the temperature dependence of the heat capacities at constant volume ( C_V ) and constant pressure ( C_P ) of CuMX2 (M = Ga and In; X = S, Se, and Te) semiconductors is systematically investigated within the framework of the combined Einstein–Debye approximation. The Einstein–Debye approximation, one of the recently refined methods for describing lattice vibrational contributions, provides improved accuracy over single-model descriptions by combining the strengths of the Debye and Einstein treatments. Calculations are carried out over a wide temperature range, and the contributions of both acoustic and optical phonon modes are incorporated through the Einstein–Debye formalism. The calculated heat capacities exhibit consistent trends among the studied compounds, reflecting the influence of atomic mass and lattice stiffness. A comparison with available theoretical and experimental literature data demonstrates good agreement, confirming the reliability of the present approach.
Halide perovskites have established themselves as a transformative class of semiconducting materials in the photovoltaic landscape, distinguished by their exceptional, synergistic combination of electronic, optical and electrical properties. Herein, lead-free methylammonium tin triiodide (MASnI3) is adopted as the absorber layer to eliminate the environmental hazards associated with lead-based perovskite compositions. This paper reports the simulation-based exploration of a potential of the electron transport layer (ETL) of zinc stannate (Zn2SnO4) coupled with diverse types of inorganic hole transport material (CuI, Cu2O, NiO, and CuSCN) in a lead-free MASnI3-based perovskite solar cell. This is the first reported configuration in which Zn2SnO4 serves as the ETL with inorganic hole transport layers (HTLs), rather than the existing configurations. Using the SCAPS-1D simulation software, the FTO/Zn2SnO4/MASnI3/HTL/Au device architecture was analyzed to identify the most suitable hole-transport layer and to optimize the device’s key parameters. Cu2O was the best-performing HTL among the tested HTLs, with an initial efficiency of solar cell device of 25.29
The formation of the cubic silicon phase (sp.gr. Fd3̅m ) was confirmed in n- and p-type silicon samples, as well as in n- and p-type tellurium-diffused silicon samples annealed for 5 h. Electron fluences of 1 × 1015, 1 × 1016, and 1 × 1017 electrons/cm2 resulted in changes to the lattice parameters of the cubic silicon phase (sp.gr. Fd3̅m ). While the phase composition of the initial and electron-irradiated samples remained essentially unchanged, irradiation led to noticeable variations in the nanocrystallite size. Hall effect measurements revealed that the resistivity of all samples increased as a function of electron fluence, and the corresponding results are presented. The resistivity of p-type silicon increased from 16.27 to 1042 Ω · cm with increasing electron fluence, while in tellurium-doped p-type samples it increased from 22.40 to 815 Ω · cm. For n-type silicon, the resistivity increased from 15.71 to 594.56 Ω · cm, whereas in tellurium-doped n-type samples it varied from 13.68 to 118 000 Ω · cm.
This study presents a comprehensive first-principles investigation into the structural, electronic, and thermal properties of pristine and doped silicon carbide nanotubes (SiCNTs), with a focus on boron and nitrogen substitution. Pristine SiCNTs exhibit characteristic Si–C bond lengths of 1.79 Å and near-planar bond angles, consistent with theoretical expectations. Doping introduces significant structural distortions, including altered bond lengths, narrowed bond angles, and increased torsional strain, which enhance steric effects and surface reactivity. Binding energy calculations confirm the thermodynamic stability of all doped configurations, with co-doping yielding the most energetically favorable structures. Electronic structure analysis reveals a substantial reduction in band gap from 2.029 eV in pristine SiCNTs to near-zero values in certain doped models driven by symmetry breaking, defect-induced states, and orbital hybridization. Density of states (DOS) analysis highlights the strong influence of dopant orbitals on the valence and conduction bands, enhancing charge carrier mobility and conductivity. Thermal analysis shows that doping significantly reduces phonon transport efficiency due to mass disorder and lattice distortions, with co-doping configurations exhibiting up to 70
Double perovskite nanoparticles of La2FeMnO6 and La2NiMnO6 were effectively prepared using combustion synthesis method. X-Ray Diffraction (XRD) and Selected Area Electron Diffraction (SAED) studies verified the formation of the double perovskite phase, with well-defined 2θ peaks corresponding to the respective crystallographic (hkl) planes. The crystallite size was estimated to be in the range of 19–25 nm. High-Resolution Transmission Electron Microscopy (HR-TEM) images revealed a predominantly spherical morphology with uniform particle distribution. Energy Dispersive X-Ray (EDX) spectra confirmed the elemental composition, confirming the presence of La, Fe, Mn, O in La2FeMnO6 and La, Ni, Mn, O in La2NiMnO6 nanoparticles. The optical band gaps were estimated to be 1.70 and 1.72 eV for La2FeMnO6 and La2NiMnO6, respectively. Fourier Transform Infrared Spectroscopy (FTIR) spectra showed characteristic vibrational bands at 425, 588, 870, and 1029 cm–1, corresponding to La3+–O2–, Fe3+–O2–, Mn3+–O2–, and Ni3+–O2– bonding vibrations. Magnetic hysteresis measurements indicated that La2FeMnO6 exhibits weak diamagnetic behavior, while La2NiMnO6 shows paramagnetic characteristics.
This work presents a stepwise structural optimization of N-polar GaN HEMTs on SiC, in which each design iteration addresses the limitations of the previous structure and moves toward a higher-performance device. Starting from an experimental baseline (gm = 270 mS/mm, fT = 18 GHz, fmax = 44 GHz, IDmax = 0.812 A/mm), Device A (Arcuate-Ended Field Plate) mitigates peak edge fields and increases gm to 316.44 mS/mm, fT to 95.68 GHz, and fmax to 170.01 GHz while raising IDmax to 1.05 A/mm and yielding BV = 240 V. However, Device A still suffers from substantial gate leakage and residual dynamic collapse. Device B (HfO2 MIS gate with partial HfO2 passivation) directly resolves Device A’s leakage and interface issues: Cgs/Cgd reduce to 0.36/0.08 pF/mm, gm rises to 380.32 mS/mm, fT/fmax improve to 135.19/251.07 GHz, IDmax increases to 1.28 A/mm, BV = 300 V, and gate leakage at VGS = 2 V falls to = 5 × 10–8 A/mm. Finally, Device C (recessed corrugated channel with a dual-dielectric HfO2/HfZrOx (HZO) gate stack) overcomes Device B’s remaining trade-offs, further lowering Cgs/Cgd to 0.30/0.06 pF/mm, boosting gm to 460.91 mS/mm and fT/fmax to 183.14/360.03 GHz, achieving IDmax= 1.50 A/mm, BV = 380 V, and ultra-low gate leakage (4.4 × 10–9 A/mm). The results demonstrate that progressive field–gate co-engineering, field-plate shaping, high-k MIS integration, and ferroelectric gating provide a practical pathway to suppress leakage and trapping while significantly improving DC and RF performance for N-polar GaN HEMTs.
In order to address the issues of fossil energy shortage and environmental pollution, developing efficient solar photovoltaic technology is particularly important. InGaN-based solar cells have wide application potential in photovoltaic fields such as space solar power stations due to their tunable bandgap, strong radiation resistance, and high-temperature tolerance. However, the power conversion efficiency is affected by factors such as In content, doping concentration, and the type and thickness of the intrinsic layer. In this study, we have investigated the effects of In content, doping concentration and thickness of i-layer on the properties of p–n and p–i–n InGaN-based solar cells with different i-layers (InGaN layer and GaN layer) using a numerical simulation method. We extracted the performance parameters of InGaN-based solar cells through I–V curves, such as Isc, Voc, FF, PCE and ideality factor, conclusions indicate that the p–n junction is optimized under ideal condition with an In content of 0.3 and doping concentrations of 1 × 1018/cm3 and 1 × 1017/cm3, and we obtained the ideal power conversion efficiency of 44.45
Lead-free inorganic tin halide perovskite CsSnI3 holds great promise for environmentally friendly photovoltaics, however it suffers from inefficient charge transport and interfacial recombination. This work presents a comprehensive numerical study using SCAPS-1D to synergistically optimize the electron transport layer (ETL, TiO2) and hole transport layer (HTL, Spiro-OMeTAD) in CsSnI3-based perovskite solar cells (PSCs). An optimal thickness of 50 nm and a carrier concentration of 1 × 1018 cm–3 for TiO2 ETL yield the device performance of 18.13
Because of their remarkable electrical, optical, mechanical, and quantum properties, two-dimensional (2D) materials like graphene, transition metal dichalcogenides (TMDs), MXenes, and h-BN have become revolutionary candidates for the creation of next-generation intelligent systems. In order to integrate 2D materials into neuromorphic computing, intelligent sensing, cyber-physical environments, and biomedical monitoring platforms, this review methodically investigates the basic mechanisms, device architectures, and sensing modalities made possible by 2D materials. In order to enable real-time environmental interpretation and decision-making, special attention is given to intelligent, adaptive, and energy-efficient operation where computation and sensing co-localize at the material level. Critical issues impacting scalabiliy and commercial viability are examined, including device-level reliability, interface engineering, defect control, and packaging tactics. Advanced fabrication and system-integration techniques, such as van der Waals heterostructures, flexible substrates, and hybrid CMOS–2D frameworks, are also described in the review. Lastly, bio-integrated neural interfaces, quantum-enhanced sensors, hybrid AI-hardware co-design, and sustainable manufacturing pathways are highlighted in a future research roadmap. All of this research points to 2D-material-based intelligent systems as a fundamental platform that can support edge-AI, smart infrastructure, and autonomous electronics in the future.
This work investigates the impact of quantum-well engineering on the performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) by comparing SQW, DQW, and TQW structures. The proposed devices incorporate progressively graded Al compositions to enhance polarization-induced charge confinement and electric field distribution. The TQW structure, comprising three heterointerfaces, demonstrates superior carrier confinement and improved electrostatic control compared to SQW and DQW counterparts. Transfer characteristics reveal that the TQW device achieves the highest drain current ( 2.5 A/mm) and steepest subthreshold slope, resulting in an improved ON/OFF ratio. Output characteristics indicate a significant enhancement in current-driving capability, with TQW showing nearly 50
