Trap Density Research Articles

High performance ternary organic photomultiplication detectors based on non-fullerene acceptor ITIC

To extend response spectrum to near infrared region, one non-fullerene acceptor ITIC was doped into P3HT:PC61BM blends, and the organic photomultiplication detectors (OPMDs) with structure of ITO/PEDOT:PSS/P3HT:ITIC:PC61BM(100:x:1, wt/wt/wt)/Al were prepared. The absorption and photoluminescence spectra of the active layer films and the current density-voltage characteristics of the devices were measured and analyzed, and the photomultiplication principle of the devices was studied. The results showed that a wide spectral response of 400–850 nm is realized in the ternary P3HT:ITIC:PC61BM active layer, and the external quantum efficiency, responsivity and specific detectivity of the ternary OPMDs based on P3HT:ITIC:PC61BM are all larger than those of the binary ones based on P3HT:PC61BM, and a maximum external quantum efficiency of 1113.71 %, specific detectivity of 6.42 × 1013 Jones and photoresponsivity of 762.99 A/W are obtained at 850 nm and under −16 V bias when the ITIC mass ratio in the ternary active layer is 4 % (i.e., x = 4). Such a considerable performance can be due to the fact that doping ITIC into P3HT:PC61BM can widen absorption spectrum of active layer to near infrared area, and increase electron trap density and exciton dissociation interfaces in active layer and create cascade energy levels for better carrier transport.

A Surface-Reconstructed Bilayer Heterojunction Enables Efficient and Stable Inverted Perovskite Solar Cells.

The efficiency of perovskite photovoltaics remains distant from their theoretical limits, primarily due to high photovoltage losses. Here a strategy is reported to minimize voltage losses by reconstructing the perovskite surface into a bilayer heterojunction (BLH) structure. Unlike conventional low-dimensional capping layers, typically constrained to a few nanometers to prevent low fill factors, this methodology facilitates a more comprehensive reaction with surface defects, allowing a more substantial capping layer (≈50 nanometers) without compromising charge transport integrity. Time-resolved microwave conductivity analysis indicates a significant reduction in trap density at the top region of the perovskite film, showing an order of magnitude lower than that of the pristine sample. Incorporating this BLH in inverted cells results in a remarkably low photovoltage deficit of 325mV, leading to a power conversion efficiency (PCE) of 26.1% (25.72% certified). The encapsulated device maintains 94% of its original efficiency after 1200h of maximum power point tracking under one sun illumination at 65°C.

Poole-Frenkel conduction in CdS single-layered and CdS/SnS2 heterojunction electrode system

In this communication, the prevalence of Poole-Frenkel conduction mechanism in two distinct semiconductor systems, CdS single-layered and CdS/SnS2 heterojunction electrode systems, is reported. X-ray diffraction (XRD) exhibits the formation of CdS quantum dots (QDs). A High resolution transmission electron microscopy (HRTEM) shows a discrete particle distribution of SnS2, tends to assemble into nanosheets. Poole-Frenkel conduction arises due to the trap distribution of CdS dots, modified by SnS2 sheets. Furthermore, the formation of heterojunctions with SnS2 shows promising enhancement in charge transport, characterized by reduced trap density and improved conductivity compared pristine CdS. The findings provide valuable insights into the fundamental charge transport processes in CdS/SnS2 system and offer potential avenues for optimizing the performance of electronic devices.

Evidence and engineering of x-ray luminescence in lead free perovskite Cs2AgInCl6 with Bi substitutions

Cs2AgInCl6 belongs to the family of lead-free halide double perovskites. Lead-free halide double perovskite appears as a viable contender for scintillator applications due to its inexpensive production costs, low intrinsic trap density, and nanosecond quick reaction. Perovskite crystals have a substantially lower trap density than lead halide and traditional oxide scintillator materials, according to thermo-luminescence measurements. Cs2AgInCl6 structure and dimensionality were engineered by Bi doping. Bi substitution reduces the bandgap, making it suited for scintillation applications. Bi substitution allows for easy tuning of Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50) due to its wide versatility in scintillation properties. For Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50), x-ray power dependent luminescence increases with increasing power. Because of their nontoxicity, sensitivity, reaction time, and stability, Cs2AgIn(1−x)BixCl6 (0 ≤ x ≤ 50) double perovskite crystals are promising for x-ray scintillation.

Design of different oxygen content and high performance bilayer In2O3 thin-film transistors at room temperature for flexible electronics

In this study, homojunction bilayer In2O3thin film transistors (TFTs) were prepared by RF-magnetron sputtering at room temperature. Herein, an active channel of bilayer In2O3TFTs are consist of the front channel with lower (poor) oxygen content and the back channel with higher (rich) oxygen content. Therefore, optimizedbilayer In2O3TFT was fabricatedandaμFE of 32.5 cm2/Vs and a small SS of 280 mV/decade, a small VTH of 0.3 Vwere achieved. In addition, small VTH shifts of 0.7 (−1.0) and 0.4 (−1.2) V under gate bias and light illumination stress tests were obtained. Through XPS band structure analysis indicated that the formation of band bending between the channel layers leads to electron injection from the back channel into the front channel, resulting in accumulation of forming carriers near the interface of the bilayer, resulting in increase the μFE of In2O3TFTs. Furthermore, XPS and LFN measurement demonstrate that control the oxygen content can reduced the oxygen-related defects and bulk/interface trap density while controlling the Ne and carrier transport in the bilayer In2O3 film,which enhance the stability of In2O3TFTs. Overall, the high-performance bilayer In2O3TFTshave opena new method to obtaine the flexible electronic devices.

Structural and Electrical Characterization of Phase Evolution in Epitaxial Gd2O3 due to Anneal Temperature for Silicon on Insulator Application

In this work, we understand the post-deposition anneal temperature effects on structural and electrical (leakage current and trap density) properties of epitaxial Gd2O3 film grown on Si (111) substrate using a cost-effective and High-Volume Manufacturing capable radio frequency sputtering method. It is found that the Rapid Thermal Annealing (RTA) at an optimum temperature of 850 °C enhances the crystallinity of the cubic phase in film. However, at higher RTA temperatures (>900 °C to 1050 °C), Si out-diffusion in Gd2O3 film is manifested as the reason for phase evolution towards the amorphous phase. The electrical characterization shows the film's low leakage current density of 100 nA/cm2. Moreover, increased breakdown voltage and field are observed with increasing RTA temperature. The frequency-dependent Capacitance-Voltage analysis shows a parallel shift accompanied by a kink at a lower frequency, indicating the presence of interface traps (Dit) with a range of time constants. After the forming gas annealing, a significant reduction in Dit is observed. The low leakage current density, low Dit and high crystallinity make Gd2O3 a promising candidate as a buried oxide in Silicon on Insulator MOSFETs.

Low-frequency noise in the Double SOI (DSOI) MOSFETs with back-gate control

In this paper, the impact of the back-gate voltage (Vb ) on the low-frequency (1/f) noise is evaluated for the 180 nm double silicon-on-insulator (DSOI) NMOS, fabricated with various thicknesses of first buried oxide (BOX1) layer (145/50 nm). Both positive and negative Vb increased the measured normalized drain current power spectral density (PSD) for more than ten-fold in DSOI standard devices with 145 nm BOX1, while the normalized PSD decreases with Vb going up in devices with 50 nm BOX1. By comparing with CNF+CMF model, interface trap density and the Coulomb scattering coefficient are extracted with the back-gate voltage applied. The interface trap density increases in standard devices for both positive and negative Vb , but decreases with increasing back-gate biasing from -10 V to 10 V in devices with 50 nm BOX1. The interface trap density shows a similar back-gate coupling effect with threshold voltage under the influence of different thickness of BOX1. The CNF and CMF noise variation under back-gate voltage can be explained by the significant fluctuation in drain current.

Low-pressure oxidation for improving interface properties and voltage instability of SiO2/4H-SiC MOS capacitor

The impact of high-temperature sub-atmospheric oxidation pressure on the interface properties of n-type 4H-SiC metal–oxide–semiconductor capacitors has been systematically investigated in this report. The bias temperature instability measurement was used to calculate the mobile ions and near-interface trap density that led to device instability at high temperatures. The density of near interface traps decreased from 88.3 × 1011 cm−2 to 10.2 × 1011 cm−2 when the growth pressure of SiO2 was reduced from 1 atm to 0.1 atm, while the mobile ions density decreased from 83.5 × 1011 to 4.18 × 1011 cm−2. The results show that SiO2 growing under lower oxidation pressure has better interfacial quality. The underlying mechanism was explored by secondary ion mass spectrometry (SIMS) and x-ray photoelectron spectroscopy (XPS). It is speculated that the SiO2/SiC interface was reconstructed under low-pressure oxidation: the excess Si-related defects near the interface, such as SiOxCy, were released while O atoms were accumulated to promote a complete oxidation reaction, thereby effectively reducing the number of defects in the SiO2 film and improving device performance.

Enhancement of dielectric constant in Sm:Zr co-doped HfO2 films synthesized by cost-effective method

Sm, Zr co-doped HfO2 films were deposited on a p-type silicon wafer using a cost-effective spin coating method. The influence of Sm, Zr co-doping concentration variation on structural, compositional, morphological, and electrical properties was examined. The dominance of the orthorhombic phase (o-phase) in comparison to the monoclinic phase was noted to rise with the simultaneous increment of Sm doping concentration and decrement of Zr concentration. A decrease in oxygen vacancies was noted for all the Sm, Zr co-doped HfO2 films from XPS results. Nonporous and uniform distribution of grains was observed from Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM) studies. Electrical studies of MOS capacitors based on Sm, Zr co-doped HfO2 films revealed a low leakage current. C-V studies exhibited an increment of dielectric constant and a decrement of interface trap densities. Further, to obtain insights into the microscopic features of Sm, Zr co-doped films, impedance and modulus studies have been performed. The obtained results imply the potential of tuning Sm, Zr co-doping concentrations in HfO2 towards stabilization of the orthorhombic phase and to enhance the dielectric constant of the films.

Impact of Deposition Temperature on Structural and Electrical Properties of Sputtered AlN/ Si (111) for CMOS compatible MEMS

Aluminium nitride (AlN) thin films are grown by reactive sputtering on Silicon (Si) with (111) orientation at low temperature (< 450 °C) for piezoelectric-based micro-electromechanical systems (MEMS). The grown AlN thin films were polycrystalline wurtzite hexagonal structure with a high texture coefficient for the (002) plane of orientation. The leakage current density by the current-voltage (I-V) measurement was found to be as low as 1.6 ×10-6Acm−2 in the grown films. The trapped charges are crucial in controlling these electrical characteristics, and low interface trap density (6.72 ×1010cm−2 eV) was observed for the sputtered AlN grown at a substrate temperature of 300 °C. This study on the structural and electrical properties of AlN/Si (111) at low substrate temperature is compatible with the complementary metal oxide semiconductor (CMOS) process for constructing piezoelectric-based MEMS devices for various applications.

A novel approach to enhancing performance and endurance in GeS2 OTS devices using amorphous carbon doped W2N electrodes

Three–dimensional (3D) cross-point (X–point) memory has gathered interest for its fast data processing and high density, achieved by stacking memory with a selector device to prevent misinterpretation. Ovonic threshold switching (OTS) is a promising selector due to its reversible switching behavior. Although, OTS devices typically employ transition metal nitrides (TMN) such as TiNx, TaNx, and WNx for electrodes owing to their good stability, high melting points, and low resistivity, TMNs can diffuse and degrade device performance by recrystallizing with chalcogenide alloys. Amorphous carbon (a–C) can be a good alternative electrode material due to its low roughness, cost–effectiveness, high work function (WF), and excellent thermal stability. However, the high resistivity of a–C (~ 150 mΩ–cm) increases threshold voltage (Vth), causing high power consumption. Therefore, combining both a–C and TMN materials can effectively obtain their advantages. This study explores the effect of varying a–C content in W2N electrodes on GeS2–based OTS selectors. The (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes were deposited using DC magnetron co–sputtering. The phase of (W2N)1-xCx (0 ≤ x ≤ 0.25) films transformed from polycrystalline to amorphous with increasing x. Devices with (W2N)1-xCx/GeS2/W2N structure showed decreased Vth and off current, improving from 4.8 to 3.8V and 8.0 to 4.17nA, respectively. The subthreshold slope, distance between traps, and interface trap density (Nit) were extracted using the Pool–Frenkel model. The reduced Vth may be attributed to a higher WF and lower Nit with increasing x. The device’s lifetime improved up to 1.0 × 109 pulses for the highest a–C content in (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes.

High-Performance perovskite quantum dots light-emitting diodes with hole transport layer engineering and synergetic outcoupling enhancement

Perovskite quantum dot light-emitting diodes (PeQLEDs) are frequently considered as the most promising alternatives to organic light-emitting diodes (OLEDs). However, the efficiency of PeQLEDs remains inferior to OLEDs due to suboptimal charge carrier transport and intrinsic light outcoupling efficiency (ηout). Herein, a combination of hole transport layer (HTL) engineering and substrate engineering is demonstrated to improve the charge injection and ηout of PeQLEDs. To replace the conventional PEDOT:PSS, a novel HTL bilayer based on modified PEDOT:PSS and PVK with a lower refractive index and fewer trap densities at the HTL-QDs interface is developed. Additionally, this study identifies the ideal thickness of ITO for achieving optimal ηout of PeQLEDs through optical simulations and experimental validation. Based on the synergistic use of HTL bilayer and 70-nm-thick ITO, the PeQLEDs achieved an optimal external quantum efficiency of 17.96 % at a luminance of 1763 cd/m2 and 15.19 % at 8300 cd/m2 without using any external outcoupling structure, indicating a low efficiency roll-off.

Suppressing Ion Migration in MAPbI3 Polycrystalline Wafer with BMIMBF4 Ionic Liquid for X‐ray Detection and Imaging

Abstract3D lead‐halide perovskite wafers, recognized for their superior photoelectronic properties and robust fabrication, are promising candidates for advanced X‐ray detectors. However, severe ion migration in 3D perovskite wafers leads to dark current baseline drift and long‐term operational instability, hindering their further development. Herein, 3D MAPbI3 polycrystalline wafers with suppressed ion migration are prepared using the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4) and systematically investigated for X‐ray detection. The BMIMBF4‐passivated MAPbI3 wafers exhibit a low defect trap density (ntrap) of 9.45 × 109 cm−3, a high ion activation energy (Ea) of 0.51 eV, a notable iodide ion migration energy barrier of 0.65 eV, and a decreased dark current drift (Idrift) of 3.56 × 10−4 nA cm−1 s−1 V−1. The optimized MAPbI3 wafer‐based detectors exhibit a high sensitivity of 12088.8 µC Gyair−1 cm−2, a low detection limit (LoD) of 107.8 nGyair s−1, and strong operational stability in X‐ray detection. Moreover, these detectors demonstrate outstanding X‐ray imaging capabilities, achieving a high spatial resolution of 5.17 lp mm−1. Consequently, the utilization of ionic liquids with pseudo‐halide anions and polarized electron density distribution provides an innovative strategy for passivating 3D perovskite, advancing the field of powder‐pressed perovskite wafer X‐ray detection.

Advanced Numerical Modeling of BaZrS3 Chalcogenide Perovskite Cells: Titanium Alloying and Back Surface Field Effects

Chalcogenide perovskites are emerging as superior alternatives to hybrid halide perovskites for photovoltaic applications due to their non-carcinogenic composition and enhanced environmental resilience, including superior resistance to moisture. This study focuses on the computational modeling of BaZrS3 (Barium Zirconium Sulfide) based solar cells, featuring a native bandgap of ∼1.71 eV. Through precise bandgap engineering via Ti alloying at the Zr site, the study aims to optimize the bandgap to the ideal range for photovoltaic efficiency. The device architecture is further refined by adjusting parameters such as layer thickness, doping densities, trap densities and metal contacts. The optimum device efficiencies at this stage were found to be 22.45 % for BaZrS3; 23.91 % for Ba(Zr0.99Ti0.01)S3; 26.64 % for Ba(Zr0.98Ti0.02)S3; and 27.74 % for Ba(Zr0.97Ti0.03)S3. Additionally, the incorporation of various back surface fields (BSFs) (CdTe, CIGS, CZTSe, Cu2Te, FeSi2, GeSe, PbS, µc-Si, SnTe, SnS, Sn2S3, and WSe2) is investigated to enhance photo-absorption. The findings indicate that a Ti alloying concentration of 3 % at the Zr site, coupled with a Cu2Te BSF, achieves the highest efficiency, approximately 30 %. These optimized structures present a robust framework for developing efficient, stable, and non-toxic photovoltaic devices utilizing chalcogenide perovskites.

Improving bias stability of IGZO field-effect transistors through CF4 plasma treatment of Al2O3 dielectrics

In this study, the effects of the CF4 plasma treatment on the amorphous indium gallium zinc oxide (IGZO) material were explored. The electrical characteristics of the IGZO-based field-effect transistor (FET) were also thoroughly examined to analyze the influence of the plasma treatment. Excellent adhesion of the sol-gel-based IGZO semiconducting film was achieved owing to the strong dipole moment of the AlOxFy layer created by the surface treatment. In particular, X-ray photoelectron spectroscopy depth profiles and transmission electron microscopy electron energy loss spectroscopy analyses provided clear evidence that fluorine atoms diffused into the Al2O3 surface via the CF4 plasma treatment. The formation of an AlOxFy layer at the IGZO/Al2O3 interface is expected to be advantageous for reducing the interface trap density, thereby enhancing the critical transistor parameters. Additionally, the plasma-treated IGZO transistor demonstrated strong electrical bias stability under continuous gate bias stress conditions. Therefore, surface modification via CF4 plasma treatment is proposed to boost the stability and performance of the device, offering a straightforward approach for integrated thin-film transistor circuitry in advanced display applications.

Characterization of Trap States in AlGaN/GaN MIS-High-Electron-Mobility Transistors under Semi-on-State Stress

Devices under semi-on-state stress often suffer from more severe current collapse than when they are in the off-state, which causes an increase in dynamic on-resistance. Therefore, characterization of the trap states is necessary. In this study, temperature-dependent transient recovery current analysis determined a trap energy level of 0.08 eV under semi-on-state stress, implying that interface traps are responsible for current collapse. Multi-frequency capacitance–voltage (C-V) testing was performed on the MIS diode, calculating that interface trap density is in the range of 1.37×1013 to 6.07×1012cm−2eV−1 from EC−ET=0.29 eV to 0.45 eV.

Synergic effects of temperature and pressure on the hydrogen diffusion and dissolution behaviour of X80 pipeline steel

Gas-phase hydrogen permeation experiments were conducted on X80 steel at temperatures from −15℃ to 60℃ and hydrogen pressures of 1, 4, 8 MPa. Hydrogen trap densities were determined, and a method for calculating nonlinear hydrogen concentration distribution was established and verified. Results reveal different temperature dependencies for hydrogen concentrations at varying pressures. At 4 and 8 MPa, the hydrogen concentration increases with temperature, whereas at 1 MPa, it initially decreases before increasing. Additionally, the influences of hydrogen pressure, hydrogen trap binding energy, and hydrogen trap density on this trend are discussed.

Enhancement of Electron Transport Characteristics Using MXene-MnFeO3 Nanocomposite Integration with Fullerene Derivatives for the Perovskite-Based Solar Cells and Detectors.

In this study, we prepared a hybrid film incorporating the MnFeO3-decorated conducting two-dimensional (2D) MXene sheet-suspended [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) electron transfer layer (ETL) for the perovskite solar cells (PSCs) and detectors. The incorporation of MXene-MnFeO3 with the PCBM ETL could drive exceptional conducting features for the PSCs. Moreover, the presence of MXene-MnFeO3 facilitated superior charge transfer pathways, thereby enhancing the electron extraction and collection processes. This enhancement was directed to improve the electron mobility within the device, resulting in high photocurrents. The designed interface engineering with the MXene-MnFeO3 nanocomposite-tuned PCBM ETL has produced a remarkable power conversion efficiency of 17.79% ± 0.27. Moreover, X-ray detectors employing PCBM modulated with the MXene-MnFeO3 ETL achieved notable performance metrics including 18.47 μA/cm2 CCD-DCD, 5.53 mA/Gy·cm2 sensitivity, 7.64 × 10-4 cm2/V·s electron mobility, and 1.51 × 1015 cm2/V·s trap density.

Low-voltage organic field-effect transistors by using solution-processable high-κ inorganic-polymer hybrid dielectrics

Organic field-effect transistors (OFETs) incorporating hybrid high-κ inorganic Al2O3 and polymer dielectrics, including polyvinyl alcohol (PVA), polystyrene (PS), or polymethyl methacrylate (PMMA), through solution-processing techniques were fabricated. The analyses revealed that the high surface energy and hydrophilicity property of Al2O3 and PVA, and the relatively hydrophobic property of PS surface, hindered the performance of corresponding OFETs. The Al2O3/PMMA-based OFET achieved the optimized performance, with a threshold voltage of −2.7 V, a hole carrier mobility of 0.056 cm2/Vs, and a current on/off ratio of 1.0 × 104 at a low operating voltage of −5 V. Through analyzing the characteristics of leakage current, capacitance, contact resistance, and trap density of OFETs, we found that the PMMA-engaged films possessed the optimized electrical properties. The introduction of PMMA eliminated the interfacial trapping, thereby lowering the threshold voltage and enhancing the performance of the device. The COMSOL Multiphysics simulation was conducted to confirm the physical mechanism. The strategy of utilizing Al2O3/PMMA hybrid dielectric could simultaneously ensure the low operating voltage and good performance of OFET, while guaranteeing the low leakage current by the thick PMMA.

Efficiency improvement of ultrathin CIGS solar cells

In this paper we present an optimization of rear-passivation parameters (cell pitch, opening width, and interface trap density) in u-CIGS solar cell using TCAD tools. The proposed investigation exhibits a significantly enhanced in understanding the beneficial effect of the rear passivation in ultrathin cell on conversion efficiency and reliability compared to existing solutions in the literature. Firstly, the device was calibrated according to the fabricated model taking in to account all material properties and defects at interfaces and within the bulk of the cells. Additional simulations demonstrate notable enhancements in cell performance due to changes in absorber thickness and doping concentration. However, traps were identified at rear u-CIGS/Al2O3 interface as a key factor degrading conversion efficiency by promoting carrier recombination. Mitigating this mechanism is essential for improving device performance. Incorporating a negative fixed charge density in the rear passivation layer offers a promising solution, providing effective field-effect passivation to minimize minority carrier recombination at the rear surface. The proposed u-CIGS solar cell device achieves an impressive efficiency of 15 % using a cell pitch of 1.5 µm and opening width of 300 nm with a fixed bandgap.