Ideality Factor Research Articles

Sol-Gel Spin Coating Synthesis and Characterization of Cadmium Zinc Phosphate Thin Films: Structural, Optical, and Electrical Properties

This study successfully implemented the sol-gel and spin coating technique to grow cadmium zinc phosphate cadmium zinc phosphate (CZP) thin films on a glass substrate and p-Si wafer. Structural and morphological analyses were conducted via X-ray diffraction (XRD) and field-emission scanning electron microscopy (SEM). Additionally, the films’ linear and nonlinear optical properties, encompassing absorbance performance, energy gap, refractive index, dielectric, conductivity, and electronegativity, were systematically studied through UV–vis spectroscopy. XRD analysis uncovers the zinc ions substitution by cadmium ions in zinc phosphate’s unit cell, generating oxygen vacancies crucial for maintaining charge neutrality. SEM images then showcase the intricate and organized nano CZP framework. Shifting to optical studies, CZP film analysis spanning 190–2500 nm reveals an indirect energy band gap of 2.92 eV. Transitioning to electrical characteristics, the CZP/p-Si junction undergoes dark mode I-V-T analysis, elucidating the ideality factor, series resistance, and barrier height.

High-current, high-voltage AlN Schottky barrier diodes

AlN Schottky barrier diodes with low ideality factor (<1.2), low differential ON-resistance (<0.6 mΩ cm2), high current density (>5 kA cm−2), and high breakdown voltage (680 V) are reported. The device structure consisted of a two-layer, quasi-vertical design with a lightly doped AlN drift layer and a highly doped Al0.75Ga0.25N ohmic contact layer grown on AlN substrates. A combination of simulation, current–voltage measurements, and impedance spectroscopy analysis revealed that the AlN/AlGaN interface introduces a parasitic electron barrier due to the conduction band offset between the two materials. This barrier was found to limit the forward current in fabricated diodes. Further, we show that introducing a compositionally-graded layer between the AlN and the AlGaN reduces the interfacial barrier and increases the forward current density of fabricated diodes by a factor of 104.

Optimizing InGaN Micro-LED Efficiency: Investigating the Internal Quantum Efficiency and Ideality Factor Connection

Optimizing InGaN Micro-LED Efficiency: Investigating the Internal Quantum Efficiency and Ideality Factor Connection

Non-thermal atmospheric jet plasma effects on the morphological, electrical and optical properties of nanocrystalline silicon

In this study, a non-thermal atmospheric argon plasma jet (NTAPJ) was designed and used to treat the porous silicon layer, prepared by photoelectrochemical etching (PECE). The porous silicon layers were distinguished before and after the cold plasma treatment utilized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL), and dark and photo current-voltage characteristics. The results confirmed the nanostructure of the formed porous silicon. After the treatment with argon plasma, the intensity of the XRD peak increased, and the porosity decreased from 93% to 62%. Additionally, porous silicon's average roughness (Sa) and root mean square (Sq) were reduced from 60.10 to 12.31nm and 73.70 to 16.53nm, respectively. The current-voltage characteristic indicated the increase in photocurrent and the ideality factor, as well as a decrease in dynamic resistance. The photoluminescence results showed a change in PL peaks, represented by a blue shift, an increase in intensity, and a vanishing of another peak.

Non-thermal atmospheric jet plasma effects on the morphological, electrical and optical properties of nanocrystalline silicon

In this study, a non-thermal atmospheric argon plasma jet (NTAPJ) was designed and used to treat the porous silicon layer, prepared by photoelectrochemical etching (PECE). The porous silicon layers were distinguished before and after the cold plasma treatment utilized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL), and dark and photo current-voltage characteristics. The results confirmed the nanostructure of the formed porous silicon. After the treatment with argon plasma, the intensity of the XRD peak increased, and the porosity decreased from 93% to 62%. Additionally, porous silicon's average roughness (Sa) and root mean square (Sq) were reduced from 60.10 to 12.31nm and 73.70 to 16.53nm, respectively. The current-voltage characteristic indicated the increase in photocurrent and the ideality factor, as well as a decrease in dynamic resistance. The photoluminescence results showed a change in PL peaks, represented by a blue shift, an increase in intensity, and a vanishing of another peak.

Superior role of V2O5 and yttrium interface layers in enhancing MIS radical photodiode performance

In this study, Cu/n-Si Schottky diodes with V2O5–Y insulating interface layer were designed for the fabrication of metal/insulator/semiconductor (MIS) structures. The effects of different Y–V2O5 interface layers placed between metals and semiconductors on the critical electrical parameters of Schottky diodes were examined. Electrical parameters of the prepared sample such as barrier height (ΦB), ideality factor (n), photosensitivity (Ps), photosensitivity (R), quantum efficiency (QE) and detectivity (D∗) were obtained from the expression. Characteristics of I–V The modification in these parameters can be attributed to the use of Schottky diodes as intermediate layers. Additionally, n, ΦB values were calculated using the thermionic emission process and the photodiode parameters Ps, R, QE and D∗ the results were compared with each other. Experiments have shown that the Schottky structure with V2O5–Y interlayer leads to higher values of Ps = 799.70 % and under the light condition of 6 wt% of Y lower value n = 2.01. This provides evidence of the improved performance of MIS models.

Revealing Bipolar Photoresponse in Multiheterostructured WTe2-GaTe/ReSe2-WTe2 P-N Diode by Hybrid 2D Contact Engineering.

The van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been thoroughly investigated with regard to practical applications. Recent studies on 2D materials have reignited attraction in the p-n junction, with promising potential for applications in both electronics and optoelectronics. 2D materials provide exceptional band structural diversity in p-n junction devices, which is rare in regular bulk semiconductors. In this article, we demonstrate a p-n diode based on multiheterostructure configuration, WTe2-GaTe-ReSe2-WTe2, where WTe2 acts as heterocontact with GaTe/ReSe2 junction. Our devices with heterocontacts of WTe2 showed excellent performance in electronic and optoelectronic characteristics as compared to contacts with basic metal electrodes. However, the highest rectification ratio was achieved up to ∼2.09 × 106 with the lowest ideality factor of ∼1.23. Moreover, the maximum change in photocurrent (Iph) is measured around 312 nA at Vds = 0.5 V. The device showed a high responsivity (R) of 4.7 × 104 m·AW-1, maximum external quantum efficiency (EQE) of 2.49 × 104 (%), and detectivity (D*) of 2.1 × 1011 Jones at wavelength λ = 220 nm. Further, we revealed the bipolar photoresponse mechanisms in WTe2-GaTe-ReSe2-WTe2 devices due to band alignment at the interface, which can be modified by applying different gate voltages. Hence, our promising results render heterocontact engineering of the GaTe-ReSe2 heterostructured diode as an excellent candidate for next-generation optoelectronic logic and neuromorphic computing.

Harnessing the synergistic effect of CuO@Fe3O4/n-Si for high-efficiency photodiodes

High-performance photodetectors were fabricated using drop-casting method, employing pure CuO, Fe3O4 and CuO@Fe3O4 nanocomposite (NC). These devices aim to achieve enhanced responsivity (R), photosensitivity (Ps), detectivity (D∗), and external quantum efficiency (EQE). The XRD results indicate that the crystallite size of the CuO@Fe3O4 NC was reduced to around 20 nm, compared to 23 nm for pure CuO and 25 nm for pure Fe3O4. In addition, phase purity and functional groups were corroborated by Raman and FTIR analysis, supporting these findings. The bandgap energy of pure CuO and Fe3O4 was estimated to be around 1.25 and 1.22 eV, respectively, while the CuO@Fe3O4 NC exhibited a lower bandgap energy of 1.13 eV due to the interface between CuO and Fe3O4. Notably, the fabricated CuO@Fe₃O₄/n-Si photodiode exhibited excellent rectification properties under illumination, with an ideality factor (n) of 2.87 and a barrier height (ΦB) of 0.83 eV. The device achieved high Ps of 773.4 %, R of 542.6 mA/W, EQE of 208.7 %, and D∗ of 2.91 × 1012 Jones, demonstrating that the CuO@Fe3O4 NC is the most effective material for photodetection in this study.

Tunneling and thermionic emission as charge transport mechanisms in W-based Schottky contacts on AlGaN/GaN heterostructures

This paper investigates the forward conduction mechanism of W-based Schottky diodes on AlGaN/GaN heterostructures across a temperature range of 25–150 °C. Current-Voltage measurements carried out at different temperatures (I-V-T), allow to identify two coexisting mechanisms for charge transport. At lower bias the conduction mechanism is ruled by tunneling (TU), with a characteristic energy of E00 = 75 meV extracted from the temperature dependence of the ideality factor. At higher bias the Thermionic Emission (TE) mechanism dominates, thus revealing the presence of an inhomogeneous barrier that increases from 0.77 to 0.94 eV with increasing the measurement temperature. An ideal barrier of 1.22 eV was extrapolated for a unitary ideality factor. Structural and electrical analyses performed at nanoscale level revealed the presence of a density of defects (dislocations) in the order of 4 × 109 cm−2. Conductive Atomic Force Microscopy (C-AFM) provided local electrical information, uncovering a significant correlation between the observed electrical characteristics and the nanoscale defect distribution. This detailed insight highlights the crucial role of the electrical characteristics of defects in influencing the tunneling current component at low bias, thereby providing valuable context for understanding the electrical behavior and performance of microscopic devices.

Increasing the efficiency of CIGS solar cells due to the reduced graphene oxide field layer of the back surface

Copper indium gallium selenide solar cells (CIGS-SCs) have gained attention due to their cost-effectiveness and environmentally friendly characteristics, making them a promising option for future electricity generation. The efficiency of CIGS-SCs can be enhanced by adding a back surface field layer (BSFL) under the absorber layer to reduce recombination losses. In this study, the electrical parameters, such as the series resistance, shunt resistance, and ideality factor, are calculated for CIGS-SCs with an advanced design, using the SC capacitance simulator (SCAPS) software. The detailed model used in the simulations considers the material properties and fabrication process of BSFL. By utilizing a reduced graphene oxide (rGO) BSFL, a conversion efficiency of 24% and a significant increase in the fill factor are predicted. This increase is primarily attributed to the ability of the rGO layer to mitigate the recombination of charge carriers and establish a quasi-ohmic contact at the metal-semiconductor interface. At higher temperatures, BSFL can become less effective due to an increased recombination and, in turn, a decreased carrier lifetime. Overall, this study provides valuable insights into the underlying physics of CIGS-SCs with BSFL and highlights the potential for improving their efficiency through advanced design and fabrication techniques.

Modelling and Analysis of Inhomogeneous Back-to-Back Schottky Junction Diode

Back-to-back Schottky diode (BBSD) is a simple device structure made from Schottky junctions that can be applied in various applications. In modelling and simulating the BBSD, the inhomogeneity of the barrier height at the Schottky interface should be considered. This paper presents device models and simulation result of an inhomogeneous BBSD. Two device models with different current spreading condition are considered. The distribution of the inhomogeneous barrier height is represented by Gaussian distribution. All the computation was done using Python programming software. When the standard deviation of the barrier height increases, the apparent barrier height that influence the electrical characteristic decreased. This is consistent with the reported experimental data. Device model that considers full current spreading showed 37.8% reduction of apparent barrier height at standard deviation of 100 meV. This is greater that the model with no current spreading. The ideality factor showed correlation with the standard deviation of barrier height, particularly when no current spreading is considered. At standard deviation of 100 meV, the ideality factor increased 2.6 %. The obtained non-unity ideality factor is associated to the significant fluctuation in the barrier height. The computed temperature-dependent current curves also showed good agreement with the reported experimental results. The device model can be a convenient tool to investigate the device operation and to validate the method used for extraction of Schottky barrier parameters.

On-Device Pressure-Tunable Moving Schottky Contacts.

Contact engineering enhances electronic device performance and functions but often involves costly, inconvenient fabrication and material replacement processes. We develop an in situ, reversible, full-device-scale approach to reconfigurable 2D van der Waals contacts. Ideal p-type Schottky contacts free from surface dangling bonds and Fermi-level pinning are constructed at structurally superlubric graphite-MoS2 interfaces. Pressure control is introduced, beyond a threshold of which tunneling across the contact can be activated and amplified at higher loads. Record-high figures of merits such an ideality factor nearing 1 and an off-state current of 10-11 A were reported. The concept of on-device moving contacts is demonstrated through a wearless Schottky generator, operating with an optimized overall efficiency of 50% in converting weak, random external stimuli into electricity. The device combines generator and pressure-sensor functions, achieving a high current density of 31 A/m2 and withstanding over 120,000 cycles, making it ideal for neuromorphic computing and mechanosensing applications.

Quantitative photocurrent scanning probe microscopy on PbS quantum dot monolayers.

Photoconductive atomic force microscopy can probe monolayers of PbS/perovskite quantum dots (QDs) with a contact area of 1-3 QDs in stable and reproducible acquisition conditions for I/V curves and photocurrent maps. From the measurements, quantitative values for the barrier height, built-in voltage, diffusion constant and ideality factor are deduced with high precision. The data analysis is based on modelling a superposition of the drift current of the photo-excited charges and a diffusion current across the interface barriers, providing physical insight into the underlying processes. Besides looking into PbS/perovskite on an indium tin oxide substrate, it is shown how the photocurrent is modified by changing either the QD ligand (to thiocyanate) or the substrate (to micro- and nanostructured gold). The dependence of the photocurrent on the light irradiance is found to follow a power law with an exponent of 0.64. Generally, quantitative measurements with high spatial resolution (on the single QD level) can provide significant insight into the processes in nanostructured hybrid optoelectronic components.

Characterization of bulk trap density using fully I–V-based optoelectronic differential ideality factor in multi-layer MoS2 FETs

Abstract Molybdenum disulfide (MoS2) has excellent optoelectronic properties, chemical stability, and a two-dimensional (2D) structure, making MoS2 a very versatile field-effect device material. Herein, we characterize MoS2 and utilize a photo-responsive I–V technique for extracting the energy distribution of the bulk traps in multi-layer MoS2 field effect transistors (FET). This method uses the differential ideality factor in both dark and light conditions. The differential ideality factor enables the efficient quantitative extraction of the device trap density by considering the nonlinear characteristics of the subthreshold region (V ON &lt; V GS &lt; V T). To accurately differentiate between the sub-bandgap traps and the interface traps near the conduction band, near-infrared light (λ= 1530 nm) optical illumination was used for the light state characterization. The bulk trap densities under dark state and light state conditions were derived for multi-layer (7-layer and 9-layer) MoS2 FET channels, and the influence of light illumination and overall multi-layer thickness on the bulk trap density was confirmed. The accurate extraction of the trap density enables the design of MoS2 FETs with long-term stability and high optoelectronic performance.

Accuracy assessment of the turbomachinery performance maps correction models used in dynamic characteristics of supercritical CO2 Brayton power cycle

The supercritical CO2 Brayton cycle (SCO2BC) has emerged as a promising next-generation power generation technology due to its potential for high thermal efficiency and compact components design. Dynamic modeling of SCO2BC is crucial for understanding and analyzing its performance under design and off-design conditions. Turbomachines are critical components in SCO2BC dynamic models. While turbomachinery components are often modeled using their design-point turbomachinery performance maps (TPM), these maps become less accurate during off-design operations. Despite the existence of various TPM correction methods that ensure model validity, the implementation of the accurate ones within dynamic SCO2BC models remains scarce in the literature. This is crucial as it potentially compromises the accuracy of the obtained results. Therefore, there is a need to investigate the errors in the existing literature TPM correction models (in dynamic SCO2BC simulation) by comparing them against dynamic SCO2BC models employing a highly accurate correction method. Thus, in the current work, the common TPM correction methods from the literature are implemented in SCO2BC dynamic models and compared against a baseline mode, which uses the highly-accurate Pham method (at both the component and cycle levels). To the authors’ knowledge, this is the first work to address this research gap for the SCO2BC dynamic simulations and on both component and cycle levels. Additionally, another novelty is the usage of Simcenter Amesim software to dynamically model the SCO2BC aided with Pham model. Multible dynamic models for both the turbomachines of SCO2BC and the whole cycle are constructed and equipped with the different TPM correction methods found in literature to compare their dynamic behaviour that of Pham model. The Ideal Gas Compressibility factor (IGZ) method demonstrates a better performance than the other tested methods, as it exhibits the lowest discrepancy compared to the Pham model. Many of the other tested methods show significant errors. Furthermore, a popular hybrid correction combining IGZ and Pham (IGZ-Ph) is also investigated. Surprisingly, while seemingly beneficial, this hybrid approach negatively impacts accuracy, even resulting in predictions as if no correction was applied.

Comparative Analysis of 50 MeV Li3+ and 100 MeV O7+ Ion Beam Induced Electrical Modifications in Silicon Photodetectors

This article investigates the impact of 100 MeV O7+ and 50 MeV Li3+ ions on Silicon Photodetectors, focusing on their electrical characteristics with similar Sn/Se ratios. Elevated ion fluences led to a significant rise in the ideality factor “n”, indicating the presence of Generation-Recombination (G-R) current due to introduced defects, especially those with deep energy levels in the forbidden gap acting as G-R centers. While Ideality factor (n) values decreased for oxygen ions at maximum fluence, they increased for lithium ions, reflecting consistent patterns in series resistance (Rs) and reverse leakage current (IR), attributed to ion-induced defects. Oxygen ions showed a monotonic variation in Rs, whereas lithium ions exhibited a slight reduction at maximum fluence, possibly due to defect annihilation. Despite differing Se values, 50 MeV Li3+ ions demonstrated improved device characteristics, suggesting potential defect annihilation. The ratio of Sn to Se indicated comparable damage contributions from nuclear and electronic energy. Additionally, TRIM computations revealed non-uniform damage distributions, with ions penetrating deep into the substrate, away from the n+/p junction.

Enhancing tetrafullerene based photosensors and photovoltaic cells by graphene oxide doping

This study explores the postulated potential of tetrafullerene as a charge transport material when combined with dispersed graphene oxide (GO), over concerns about fullerene’s limited performance in similar devices. Incorporating GO is expected to augment carrier concentration, increase surface area, and reduce operating voltages. Devices fabricated with p-Si/tetrafullerene with varying GO concentration exhibit notable enhancements in both dark and illuminated characteristics. The results demonstrate improved electron concentration and transport, leading to enhanced rectification ratios, ideality factors, and interface state densities across a broad bias and illumination range. Notably, devices doped with 0.2GO exhibit the most promising electrical and photoresponse characteristics, showcasing potential for applications in photosensing and photovoltaics.

Fabrication of Al/n-GaN/p-Si/Al diodes by thermal evaporation and evaluation of effect of gamma irradiation on device properties

This study investigates the impact of γ-irradiation on the material and device properties of Al/n-GaN/p-Si/Al heterojunction diodes. GaN thin films were deposited on glass and p-Si substrates using thermal evaporation, followed by annealing at 450 °C. The diodes were subjected to γ-irradiation doses of 0, 3, and 6 kGy. X-ray diffraction (XRD) measurements revealed significant structural changes, including phase transitions influenced by radiation. Electrical characteristics were assessed through current–voltage (I-V) measurements within the ± 2 V range. Notably, the ideality factor for the annealed diodes improved from 6.60 to 4.62 and 3.85 with increased γ-irradiation. The barrier height was determined to be 0.85 eV, and it did not exhibit a significant change upon γ-irradiation dose. The results provided valuable insights into the response of heterojunction diodes to radiation exposure, aiding in the understanding and potential improvement of the radiation resistance of GaN-based electronic devices.

A Study on the Impact of Different PV Model Parameters and Various DC Faults on the Characteristics and Performance of the Photovoltaic Arrays

PV systems play a vital role in the global renewable energy sector, and they require accurate modeling and reliable performance to maximize the output power. This research presents a thorough analysis and discussions on the effects of different PV models’ parameters and certain specific faults on the performance and behavior of the photovoltaic systems under different temperature and irradiation conditions. It provides a detailed analysis of how several parameters affect the performance of the PV arrays, for instance, the series resistance, shunt resistance, photocurrent, reverse saturation current, and the diode ideality factor. These parameters were extracted mathematically and verified with the help of wide-ranging simulations and practical experiments. Additionally, the investigation of the effect of DC faults, including line-to-line, line-to-ground, partial shading, and complete shading faults on PV arrays, provides important fundamentals for fault detection and classification, thus improving the efficiency and protection of PV systems. It can, therefore, be stated that the outcomes of this research will assist in the enhancement of PV systems in terms of design, operation, and maintainability of photovoltaic plants, as well as contribute positively to the advancement of sustainable solar energy technology.

The influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes

In this work we present studies on the influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes. Obtained results shows substantial effect of oxygen partial pressure on the electrical properties of NiO/β-Ga2O3 heterojunction diodes. The diodes with NiO layers deposited in pure Ar shows Schottky-like I-V characteristics with low ideality factor of 1.05 and barrier height of 1.27 eV as well as low turn-on voltage close to 1V. On the other hand, diodes with NiO layer deposited in oxygen containing atmosphere shows typical p-n diode characteristics. The best electrical characteristics i.e. low on-state resistance of 2.85 mΩcm2, lack of defects and low ideality factor down to 1.07 at RT along with high breakdown voltage close to 900V without any junction termination, were obtained for diodes with NiO layers deposited at 50 % oxygen content. We have demonstrated that by optimization of oxygen partial pressure, the properties of NiO/β-Ga2O3 heterojunction diodes can be tuned and excellent electrical performance in terms of low-on state resistance, high breakdown voltage, low-leakage current and low ideality factor, can be obtained.