Degradation Of Device Performance Research Articles

Interfacial Optimization for AlN/Diamond Heterostructures via Machine Learning Potential Molecular Dynamics Investigation of the Mechanical Properties.

AlN/diamond heterostructures hold tremendous promise for the development of next-generation high-power electronic devices due to their ultrawide band gaps and other exceptional properties. However, the poor adhesion at the AlN/diamond interface is a significant challenge that will lead to film delamination and device performance degradation. In this study, the uniaxial tensile failure of the AlN/diamond heterogeneous interfaces was investigated by molecular dynamics simulations based on a neuroevolutionary machine learning potential (NEP) model. The interatomic interactions can be successfully described by trained NEP, the reliability of which has been demonstrated by the prediction of the cleavage planes of AlN and diamond. It can be revealed that the annealing treatment can reduce the total potential energy by enhancing the binding of the C and N atoms at interfaces. The strain engineering of AlN also has an important impact on the mechanical properties of the interface. Furthermore, the influence of the surface roughness and interfacial nanostructures on the AlN/diamond heterostructures has been considered. It can be indicated that the combination of surface roughness reduction, AlN strain engineering, and annealing treatment can effectively result in superior and more stable interfacial mechanical properties, which can provide a promising solution to the optimization of mechanical properties, of ultrawide band gap semiconductor heterostructures.

Theoretical simulation of mixed organic–inorganic perovskite solar cell using SCAPS-1D simulator

In this work, a triple cation mix halide perovskite solar cell is explored to improve its stability and efficiency. FTO/SnO2/perovskite/CuSCN/carbon the device structure is simulated using SCAPS-1D and outcomes and found in good agreements with experimental results. Furthermore, the effect of various parameters like absorbance coefficient, reflection of front surface, defect capture cross section and defect position on device performance are examined. This optimized device exhibits high PCE, 27.10 % with Voc = 1.24 V, Jsc = 25.37 mA/cm2 and FF = 85.70 %. Finally, the effects of temperature, absorber defect density and interface defect density are computed on optimised structure and observed degradation in device performance with increase in these factors. Lastly, the results are concluded using J-V and EQE curves. This study may be vital in the development of stable and highly efficient triple cation perovskite solar cell technology.

Enhancing ferroelectricity in HfAlOx-based ferroelectric tunnel junctions: A comparative study of MFS and MFIS structures with ultrathin interfacial layers

This study explores the potential advantages of metal–ferroelectric–insulator–semiconductor (MFIS) structures compared with established metal–ferroelectric–semiconductor (MFS) and metal–ferroelectric–metal structures in the context of nonvolatile memory devices. Despite the superior performance of MFS structures in terms of electric field maintenance, switching speed, and power consumption, the presence of interface-related issues between the ferroelectric material and the semiconductor may degrade device performance. We propose an MFIS structure incorporating ultrathin interfacial layers (ILs) of SiO2, HfO2, and ZrO2 to address these issues. These insulator layers enhance device endurance by reducing physical stress and trap density at the interface, thereby improving electrical performance and long-term stability. Moreover, the presence of an IL reduces charge leakage between the ferroelectric layer and semiconductor, contributing to the resolution of the sneak path current problem. An additional feature of MFIS devices is their self-rectifying behavior, simplifying circuit design and manufacturing processes by eliminating the need for an external rectification circuit, consequently reducing costs. Through a series of experiments, this study evaluates the performance of the MFIS structure, investigates the ferroelectric properties of HfAlOx-based FTJs, and examines the conduction mechanism of the MFIS structure. By comparing the o-phase of MFS, SiO2, HfO2, and ZrO2 devices via grazing incidence X-ray diffraction (GIXRD) and using the positive-up-negative-down method to extract polarization and coercive voltage, we provide a comprehensive investigation of the impact of ultrathin ILs on ferroelectric properties. This research aims to offer valuable insights into the advancement of memory device technologies, presenting the MFIS structure as a promising platform for next-generation memory technologies. Further sections will elaborate on the experimental setup, methodology, and detailed study findings.

Multivariable degradation modeling and life prediction using multivariate fractional Brownian motion

In system prognostics and health management, multivariable degradation models have been widely developed to predict the life of complex systems using degradation data of multiple Performance Characteristics (PCs). Recent studies have detected a Long-Term Memory (LTM) effect among the degradation process of various PCs, implying a strong coupling phenomenon between the future degradation behavior and historical degradation trajectory. Although the LTM has been widely integrated into single-PC-based degradation modeling, it has not been considered in multi-PC-based scenarios. To capture LTM among multiple PCs, this article proposes a novel LTM-integrated Multivariate Degradation Model (MDM) for system life prediction based on multivariate fractional Brownian motion, which simultaneously incorporates the cross-correlation among different PCs. To estimate parameters of the LTM-integrated MDM, a maximum likelihood method is developed. Two likelihood-ratio hypothesis tests are developed to test the existence of the overall and individual LTM effect among multiple PCs. Both simulation studies and physical experiments on the performance degradation of solar energy conversion and storage devices are conducted to validate the proposed model. Results reveal that the proposed LTM-integrated MDM significantly outperforms existing MDMs in life prediction, while the lifetime uncertainty is heavily underestimated by those traditional approaches that neglect the LTM.

Flexible resistive memory device with egg-albumen/HfO x hybrid bilayer: fabrication and modeling of its switching variations

Egg-albumen, a natural polymer, in bilayer combination with ultrathin HfO x is explored as an active switching layer component in flexible resistive random access memory devices. The fabricated devices have shown excellent switching characteristics with a current on/off ratio of greater than 104, stable retention of both low resistance and high resistance states, reliable multiple cycle switching, and very low switching power (with set power as 0.5 µW and reset power as 3.1 mW). To investigate the electro-mechanical stability, devices were bent with different bending radii and it was found that negligible degradation in device performance was observed until a 5 mm bending radius. Furthermore, a simple mathematical model is used to simulate the devices’ characteristics and the values of fitting parameters were extracted with a root mean square error of less than 4.5%. Moreover, a switching variation was introduced by utilizing variations of the physical parameters, and a near practical physics based mathematical device model was demonstrated which can enable the strengthening of simulation capabilities for exploration of unique flexible resistive memory devices and related circuits.

Demonstration of GaN-channel high electron mobility transistors with regrown InAs/GaAs source and drain

We demonstrated the crystal growth of group-III arsenides (III-As) on GaN via an arsenidation layer and GaN-channel electron mobility transistors (HEMTs) with a regrowth InAs/GaAs source and drain (S/D) region. By annealing under an AsH3 atmosphere, the surface of a GaN (0001) template is arsenided. We grew ⟨111⟩ oriented InAs and GaAs on arsenided GaN. Silicon-doped n-type InAs with a carrier mobility of over 1500 cm2/V s and a carrier concentration of over 1 × 1019 cm−3 was successfully obtained. The fabrication process and direct-current characteristics of GaN-channel HEMTs with the regrown Si-doped InAs/GaAs S/D region were demonstrated for the first time. A maximum transconductance estimated from transfer characteristics was as high as ∼195 mS/mm for the HEMT with a gate length of 2 μm without passivation, which is comparable to those for the HEMT without any S/D regrowth. The impact of the InAs/GaAs S/D region on the on-resistance of the fabricated HEMTs was estimated to be ∼0.9 Ω mm, which can be reduced by optimizing the device structures and process conditions. These results indicate that the process of GaN arsenidation and III-As regrowth can be used without any device performance degradation. Therefore, further lowering the ohmic contact resistivity and on-resistance of GaN-channel HEMTs is possible by maturing the manufacturing-process technology of III-As-contained GaN-channel HEMTs.

Effect of mild mechanical stresses on device physics of slot-die coated flexible perovskite solar cells

Halide perovskites are a promising class of novel photoactive materials for their application in flexible photovoltaic devices. Tolerance and stability of devices to various mechanical stresses are important aspects of this technology for its effective and long-term operation. Currently, this aspect has not been fully researched and addressed by the research community. Hence, this work is aimed at studying the effect of mild mechanical stresses (MMSs) induced by convex bending on the behaviour of ITO/ZnO/MAPbI3/Spiro-OMeTAD/Au slot-die-coated flexible perovskite solar cells (FPSCs) and investigating the underlying mechanisms leading to performance degradation in devices. The carrier generation, recombination, and extraction processes within FPSCs are investigated before and after the application of MMSs. The obtained results suggest that the photovoltaic performance of the FPSCs deteriorates by up to 50% after convex bending, due to increased non-radiative recombination losses. The results obtained in this work provide some valuable insights into the dynamics of recombination processes in FPSCs exposed to MMSs and can be used for developing new strategies for improving the mechanical stability of devices.

TCAD simulation study of heavy ion radiation effects on hetero junctionless tunnel field effect transistor

Semiconductor devices used in radiation environment are more prone to degradation in device performance. Junctionless Tunnel Field Effect Transistor (JLTFET) is one of the most potential candidates which overcomes the short channel effects and fabrication difficulties. In this work, 20 nm JLTFET is proposed with Silicon in the drain/channel region whereas source uses different materials, Silicon Germanium (SiGe), Gallium Nitride (GaN), Gallium Arsenide (GaAs), Indium Arsenide (InAs). The device performance is examined by subjecting it to heavy ion radiation at a lower and higher dose of linear energy transfer (LET) values. It can be seen that the most sensitive location is the source/channel (S/C) interface for SiGe, GaN and GaAs whereas the drain/channel (D/C) interface for InAs. Further analysis is carried out at these vulnerable regions by matching ION of all materials. The parameters, transient peak current (Ipeak), collected charge (QC), threshold voltage shift (ΔVth) and bipolar gain (β) are extracted using transient simulations. It is observed that for a lower dose of LET, Ipeak of SiGe is 27% lesser than InAs and for higher dose of LET, SiGe shows 56% lesser Ipeak than InAs. SiGe is less sensitive at lower and higher dose of LET due to reduced ΔVth, tunneling and electron density.

Charge transport and ion migration in perovskite-incorporated conjugated polymer semiconductor

The migration of intrinsic ions in metal halide perovskites and their interfaces has been shown to contribute to hysteresis and performance degradation in perovskite-based electronic devices, particularly in photovoltaics and transistors. Accordingly, controlling the film morphology, microstructure, and ionic defects in perovskite semiconductors is essential for advancing and achieving high-performance perovskite field-effect transistors (FETs). In this study, we demonstrate a well-controlled method to systematically probe the structure-property relationships, origin of hysteresis, and intrinsic ion migration effects in formamidinium iodide and lead iodide (FAI + PbI2)-based perovskite by incorporating it in a semicrystalline conjugated poly(3-hexylthiophene) (P3HT) polymer. Optimized FETs exhibited over 100% hole mobility enhancement owing to unperturbed edge-on crystalline orientation of the P3HT chains caused by the incorporated perovskite, P3HT-(FAI + PbI2) interactions, and better charge injection properties. However, the optimized devices exhibited improved current modulation with dual-sweep hysteresis, which was attributed to the ion migration effect contributed by the polarization of the lead/iodine-related ions and defects. Furthermore, operational stability investigation of the P3HT-(FAI + PbI2) FETs in the air revealed gradual current decay owing to charge trapping in contrast to the control P3HT FETs. This work provides a fundamental understanding of the origin of hysteresis and instabilities in metal perovskite materials and their transistor-based devices.

Acid molecule-assisted high-quality SnO2 transport layer for perovskite solar cells

The SnO2 electron transport layer (ETL) serves a critical role in perovskite solar cells. However, the oxygen vacancy defects and excess hydroxyl (–OH) groups in SnO2 always lead to degradation of device performance. Herein, we introduce iminodiacetic acid (IDA) to modify the SnO2 ETL, yielding three key advantages: (1) IDA can neutralize excess –OH groups and passivate the defects in SnO2, diminishing the decomposition of perovskite layer; (2) the IDA-modified SnO2 exhibits superior electron conductivity and film quality, while providing improved energy level alignment with the perovskite layer; and (3) the IDA-modified SnO2 owns superior surface wetting properties that facilitates a more effective perovskite crystallization. Ultimately, the devices based on IDA-modified SnO2 obtain a champion efficiency of 24.02% and enhanced stability.

First-principles study on the effects of fast neutron irradiation and fast neutron irradiation under the external electric field on carbon-based material AB bilayer graphene

The irradiation damage mechanism of fast neutron irradiation and the fast neutron irradiation under the practical application of an additional electric field on carbon-based material AB bilayer graphene is not yet clear. This paper systematically investigates the impact of fast neutron irradiation and fast neutron irradiation under the practical application of the additional electric field (−0.2 V/Å) on carbon-based material AB bilayer graphene through density functional theory and molecular dynamics simulations. The research results indicate that the changes in the configuration of AB bilayer graphene and the appearance of surface ripples induced by fast neutron irradiation are the two main reasons for the alterations in the system's microstructure, band structure, Young's modulus, and optical properties, which may lead to performance degradation and damage of carbon-based devices. The further variation in the average interlayer spacing of the system under external electric field irradiation leads to the diversity of the system configuration, which ultimately leads to the diversity of the band structure of the system. The uncertainty in the type and width of the bandgap in AB bilayer graphene under fast neutron irradiation with an external electric field may be one of the reasons for the performance degradation and permanent damage of carbon based devices in practical applications. In the fast neutron irradiation environment, the precise control of the bandgap of AB bilayer graphene by an applied electric field will fail.

Luminescent Solar Concentrator with Advanced Structure for Reabsorption Loss Suppression and Synergistic Energy Harvesting

AbstractAs large‐area and optically transparent photon harvesting devices, luminescent solar concentrators (LSCs) are promising candidates for building‐integrated photovoltaics owing to their high transmittance and resistance to shadowing effects existing in solar cells. Up to now, there are still many challenges in the practical application of LSCs: 1) Reabsorption loss is inevitable during photoluminescence transmission due to indirect illumination of solar cells in LSC system. 2) Satisfactory energy harvesting cannot be achieved in rainy conditions due to the substantial attenuation of the incident light intensity. 3) Evaporation residue on the surface of LSCs leads to device performance degradation. Pioneering researches and feasible strategies for reabsorption loss suppression, energy harvesting in rainy days as well as self‐cleaning property are still lacking demonstration. In this work, reabsorption loss is suppressed based on advanced structural LSCs with universally applicable optical spacer layer. Then the integrated LSCs with droplet‐based electricity generator (DEG) are proposed for the first time. Such DEG‐LSCs not only realize synergistic harvesting of solar and raindrop energy, but also possess self‐cleaning properties. Finally, a self‐powered temperature and humidity sensing system is designed and demonstrated to provide feasible ideas for the practical application of DEG‐LSCs in self‐powered intelligent buildings.

Understanding and Mitigating Atomic Oxygen-Induced Degradation of Perovskite Solar Cells for Near-Earth Space Applications.

Combining high efficiency with good radiation tolerance, perovskite solar cells (PSCs) are promising candidates to upend expanding space photovoltaic (PV) technologies. Successful employment in a Near-Earth space environment, however, requires high resistance against atomic oxygen (AtOx). This work unravels AtOx-induced degradation mechanisms of PSCs with and without phenethylammonium iodide (PEAI) based 2D-passivation and investigates the applicability of ultrathin silicon oxide (SiO) encapsulation as AtOx barrier. AtOx exposure for 2h degraded the average power conversion efficiency (PCE) of devices without barrier encapsulation by 40% and 43% (w/o and with 2D-PEAI-passivation) of their initial PCE. In contrast, devices with a SiO-barrier retained over 97% of initial PCE. To understand why 2D-PEAI passivated devices degrade faster than less efficient non-passivated devices, various opto-electrical and structural characterications are conducted. Together, these allowed to decouple different damage mechanisms. Notably, pseudo-J-V curves reveal unchanged high implied fill factors (pFF) of 86.4% and 86.2% in non-passivated and passivated devices, suggesting that degradation of the perovskite absorber itself is not dominating. Instead, inefficient charge extraction and mobile ions, due to a swiftly degrading PEAI interlayer are the primary causes of AtOx-induced device performance degradation in passivated devices, whereas a large ionic FF loss limits non-passivated devices.

Morphological Homogeneity and Interface Modification as Determinant Factors of the Efficiency and Stability for Upscaling Organic Solar Cell.

Morphological homogeneity and interfacial traps are essential issues to achieve high-efficiency and stable large-area organic solar cells (OSCs). Herein, by the investigation of three quinoxaline-based acceptors, i.e., PM6:Qx-1, PM6:Qx-2, and PM6:Qx-p-4Cl, the performance degradation in up-scaling OSCs is explored. The inhomogeneous morphology in PM6:Qx-2 induces a nonuniform spatial distribution of charge generation, showing a rapid decline in efficiency and stability in large-area OSCs. In comparison, the homogeneous morphology in PM6:Qx-1 and PM6:Qx-p-4Cl alleviates the stability drop. When utilizing 2-phenylethylmercaptan to fill the interfacial traps, the stability drop disappears for PM6:Qx-1 and PM6:Qx-p-4Cl, while it persists for PM6:Qx-2. The PM6:Qx-1 large-are device yields a high efficiency of 13.47% and superior thermal stability (T80 = 2888h). Consequently, the interface modification dominates the performance degradation of large-area devices with homogeneous morphology, while it cannot eliminate the traps in inhomogeneous film. These results provide a clear understanding of degradation mechanisms in upscaling devices.

Study on stress in trench structures during silicon IGBTs process-oxidation

In silicon insulated gate bipolar transistors, the trench gate structure is used to achieve smaller cell size and lower ON resistance, and thereby reduces energy loss. However, the thermal process can cause large stress near the trench and sometimes degrades device performance. This study proposed a three-dimensional model of a silicon chip with trench structures to analyze the stress distribution induced by thermal process around the trench, the scribe line, and the bottom surface of the chip. The calculated stress is in good agreement with measurement by Raman spectroscopy. The mesa top has much higher stress than the scribe line and the bottom surface. The stress depends on oxide thickness and the size scaling may reduce the stress.

Quantitative analysis of performance degradation in movable MEMS devices by a multiscale approach

The rapid advancements in AI and 5G/6G communication technologies have intensified the demand for MEMS devices characterized by exceptional performance and diversity. Simultaneously, the imperative for enduring stability in these devices has become increasingly critical. Unforeseen reliability issues pose substantial challenges to the full-scale application of these advanced MEMS devices, underscoring the importance of understanding their failure mechanisms. Presently, there is a scarcity of comprehensive research in reliability computation and analysis. In this study, we adopt cross-scale damage variables as a nexus, linking responses across three scales: material, structural, and performance. We implement a synergistic finite element-molecular dynamics approach for multiscale analysis. Using a prototypical MEMS resonator structure as a case study, we establish quantitative interrelations among these three scales, enabling precise depiction of atomic failure behavior and its impact on resonant frequency degradation. This approach offers an atomically grounded explanation for the fundamental material processes underlying frequency degradation. Our numerical analyses explore the failure mechanisms responsible for the frequency degradation in MEMS resonators. Additionally, we propose several optimized strategies for the design and preparation phases aimed at enhancing fatigue performance. These findings are particularly relevant in light of the growing necessity for devices that maintain long-term stability.

Efficient Tin-Based Perovskite Solar Cell with a Cesium Acetate Pre-buried PEDOT:PSS Hole Transport Layer.

The strong Lewis acid tin halide leads to an excessively fast crystallization rate, resulting in more defects in the film and degraded device performance. In this work, a cesium acetate (CsAc) pre-buried poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer acts as nucleation points during the crystallization of tin-based perovskite, which can induce preferential orientation growth of crystals and increase the grain size to improve the quality of crystallization. The addition of CsAc not only can increase the conductivity of PEDOT:PSS but also can improve the wettability of the perovskite precursor solution to enhance the interface contact between the hole transport layer and perovskite layer. Because of the incorporation of CsAc in PEDOT:PSS, the average short-circuit current density increases from 23.80 to 27.60 mA cm-2. Furthermore, a power conversion efficiency of 10.99% is achieved for a tin-based perovskite solar cell with CsAc-doped PEDOT:PSS as the hole transport layer.

Tuning phase separation in DPPDTT/PMMA blend to achieve molecular self-assembly in the conducting polymer for organic field effect transistors.

The semiconductor/insulator blends for organic field-effect transistors are a potential solution to improve the charge transport in the active layer by inducing phase separation in the blends. However, the technique is less investigated for long-chain conducting polymers such as Poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPPDTT), and lateral phase separation is generally reported due to the instability during solvent evaporation, which results in degraded device performance. Herein, we report how to tailor the dominant mechanism of phase separation in such blends and the molecular assembly of the polymer. For DPPDTT/PMMA blends, we found that for higher DPPDTT concentrations (more than 75%) where the vertical phase separation mechanism is dominant, PMMA assisted in the self-assembly of DPPDTT to form nanowires and micro-transport channels on top of PMMA. The formation of nanowires yielded 13 times higher mobility as compared to pristine devices. For blend ratios with DPPDTT ≤ 50%, both the competing mechanisms, vertical and lateral phase separation, are taking place. It resulted in somewhat lower charge carrier mobilities. Hence, our results show that by systematic tuning of the blend ratio, PMMA can act as an excellent binding material in long-chain polymers such as DPPDTT and produce vertically stratified and aligned structures to ensure high mobility devices.

Enhanced Performance of Metal‐Semiconductor‐Metal UV Photodetectors on Algan/Gan Hemt Structure via Periodic Nanohole Patterning

AbstractAlGaN/GaN High Electron Mobility Transistor (HEMT) structures offer superior electrical and material properties that make them ideal for the fabrication of high‐performance Ultraviolet photodetectors (UV PDs), especially using the metal‐semiconductor‐metal (MSM) configuration. However, the metal layout of the MSM design and crystal defects in multi‐stack HEMTs can reduce photocurrent and degrade device performance. Nano‐structuring of the AlGaN/GaN surface with different nanofeatures is a promising approach to improve light absorption efficiency and increase device response. In this work, AlGaN/GaN HEMT MSM UV photodetectors with enhanced performance parameters by engineering the surface with periodic nanohole arrays are demonstrated. Optical simulations are used to optimize the design of the nanoholes' periodicity and depth. Unpatterned and nanohole‐patterned devices with varying nanohole depths are fabricated, and their performance shows substantial enhancement with the incorporation of nanoholes. The device with 40 nm deep nanoholes and 230 nm array periodicity shows the highest performance in terms of photocurrent (0.15 mA), responsivity (1.4 × 105 A W−1), UV/visible rejection ratio (≈103), and specific detectivity (4.9 × 1014 Jones). These findings present a HEMT‐compatible strategy to enhance UV photodetector performance for power optoelectronic applications, highlighting that nanohole patterning is a promising prospect for advancements in UV photodetection technology.

A novel microchannel heat sink with staggered inlet and outlet to improve base surface temperature uniformity

Non-uniform temperature distribution can lead to performance degradation and thermal failure of electronic devices. So as to improve the base surface temperature uniformity, we proposed a novel microchannel heat sink with staggered inlet and outlet. This arrangement divides a complete flow channel into three regions, and the flow direction in each channel can be changed to form different flow modes. The effects of flow mode, the inlet and outlet spacing, Reynolds number and channel length on the temperature uniform performance of base heating surface are investigated numerically. It is found that the microchannel heat sink with staggered inlet and outlet has more uniform fluid distribution and can ensure the same highest temperature in each region to improve the base surface temperature uniformity. The optimal spacing between middle inlet and outlet decreases as Reynolds number decreases for optimal flow mode, and the improving effect of temperature uniformity becomes worse with increasing channel length. Within the calculation parameter range, compared with the straight microchannel unit, the base temperature difference and the pumping power of staggered microchannel unit with countercurrent flow in each region are reduced by 77.6% to 81.3% and 56.1% to 68.8%, respectively.