Device Structure Research Articles

Depth-of-field enhancement in light field display based on fusion of voxel information on the depth plane

To improve the performance of 3D light field display(LFD) devices and optimize their display effects, a depth-of-field (DOF) enhancement in LFD based on fusion of voxel information on the depth plane is proposed. In previous research, a calculation method was developed to calculate the voxel size on the depth plane. According to this calculation method, a distribution model of voxel varying with display depth is established. A DOF determination criterion based on voxel distribution from visual perspective is proposed, and its accuracy is validated through subjective experiments involving multiple participants. By fusing the voxels on the depth plane, the phenomenon of voxel overlap is improved, resulting in enhanced definition of 3D images on the depth plane. Under the condition that the structure and parameters of the 3D LFD device are determined, the maximum achievable display depth will be increased significantly. Finally, experimental validation of the method's feasibility is conducted using multiple 3D light field devices for display.

Efficiency optimization of All-Inorganic perovskite solar cell device using NiOx and ZnO as charge transport layers

In this study, we have developed and refined an all-inorganic perovskite solar cell with the structure FTO/ZnO/CsPbBr3/NiOx/Au. This was accomplished by incorporating the inorganic perovskite CsPbBr3 and the inorganic charge transport layers ZnO and NiOx. We employed solvent engineering techniques such as dropping solvents like isopropyl alcohol (IPA) and ethyl acetate (EA) during the spin-coating process, along with optimizing the thickness of the absorber layer and annealing conditions to enhance the power conversion efficiency (PCE). Our evaluation of the impact of the CsPbBr3 absorption layer thickness on PCE revealed that efficiency improved with layer thicknesses up to 280 nm. Moreover, we investigated the influence of post-deposition annealing durations on CsPbBr3, experimenting with times of 0.5hr, 1hr, 2hr, 3hr, and 5hr. The optimal conversion efficiency of 0.91 % was attained with an annealing temperature of 225 °C for 2hr, particularly when the absorption layer thickness was set at 280 nm. These results suggest that the device structure optimization for all-inorganic perovskite quantum dot solar cells can be successfully applied for efficiency optimization.

A Unique Time-Reversal Algorithm-Enabled Flexible Ultrasound Transducer with a Controllable Acoustic Field.

Flexible ultrasonic devices represent a feasible technology for providing timely signal detection and even a non-invasive disease treatment for the human brain. However, the deformation of the devices is always accompanied by a change in the acoustic field, making it hard for accurate focusing. Herein, we report a stable and flexible transducer. This device can generate a high-intensity acoustic signal with a controllable acoustic field even when the device is bent. The key is to use a low-impedance piezoelectric material and an island-bridge device structure, as well as to design a unique time-reversal algorithm to correct the deviation of signals after transcranial propagation. To provide an in-depth study of the acoustic field of flexible devices, we also analyze the effects of mechanical deformation and structural parameters on the corresponding acoustic response.

Gate mesa terminal with drain-field-plated β-Ga2O3 MOSFET with ultra-high power figure of merit

In this article, a novel gate mesa terminal (GMT) device structure incorporating a drain field plate is proposed. This design features mesa terminals with varying bevel angles positioned atop the gate. The objective is to enhance the breakdown voltage (Vbr) and reduce the on-resistance (Ron) of the lateral β-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET). Through the implementation of the GMT structure, the peak electric field within the β-Ga2O3 MOSFET is redirected towards the passivation layer. This effectively mitigates the electric field in the epitaxial layer, thereby increasing Vbr. The optimal values for Vbr, specific on-resistance (Ron,sp) and maximum transconductance (gm) across various GMT structures are 4827 V, 9.9 mΩ·cm2 and 15.32 mS/mm, respectively. These metrics represent a 2.63-fold, 0.88-fold, and 1.25-fold improvement compared to the non-GMT structure. Additionally, when the doping concentration of epitaxial layer is 1 × 1016 cm−3, the GMT achieves an enhanced threshold voltage of +0.26 V. By simulating different bevel angles, field plate parameters, epitaxial layer doping concentrations, and mesa thicknesses, an optimal power figure of merit (PFOM) of 1.914 GW cm−2 is attained. This innovative design introduces a fresh concept for the development of the next generation of high voltage and high-power devices rated above 4 KV.

Electroplating nickel patterns onto polyol-mediated reduced graphene oxide printed textile surfaces

This report explores advancements in multi-step printing/electroplating technique for creating conductive patterns on flexible substrates, which serve as potential structures in wearable electronic devices. The study introduces a novel procedure that employs a sequential process involving polyol screen printing and electroplating, enabling the development of conductive nickel-coated patterns with a conductivity value of about 1123 S/cm on textiles. A significant innovation in this study is the use of a graphene oxide/ethylene glycol (GO/EG) ink, which can be converted into reduced graphene oxide (rGO) through in-situ polyol treatment on the surface of PET fabrics. The effectiveness of this treatment is evidenced by various analytical and microscopic techniques, which confirm the successful printing of conductive rGO patterns onto PET fabric at 220 ˚C. The printed rGO patterns on the fabric surface are then subjected to electroplating as a target substrate and cathode for varying durations, ranging from 5 to 30 minutes. The study thoroughly examines the influence of electroplating time on the microstructures and electrical conductivity of the resulting patterns, with nickel deposition reaching up to 50.8 mg/cm².

Recent Advances in Flexible Self-Powered Sensors in Piezoelectric, Triboelectric, and Pyroelectric Fields

The rise of the Internet of things has catalyzed extensive research in the realm of flexible wearable sensors. In comparison with conventional sensor power supply methods that are reliant on external sources, self-powered sensors offer notable advantages in wearable comfort, device structure, and functional expansion. The energy-harvesting modes dominated by piezoelectric nanogenerators (PENGs), triboelectric nanogenerators (TENGs), and pyroelectric nanogenerators (PyENGs) create more possibilities for flexible self-powered sensors. This paper meticulously examines the progress in flexible self-powered devices harnessing TENG, PENG, and PyENG technologies and highlights the evolution of these sensors concerning the material selection, pioneering manufacturing techniques, and device architecture. It also focuses on the research progress of sensors with composite power generation modes. By amalgamating pivotal discoveries and emerging trends, this review not only furnishes a comprehensive portrayal of the present landscape but also accentuates avenues for future research and the application of flexible self-powered sensor technology.

Recent Advances of Photodetection Technology Based on Main Group III–V Semiconductors

AbstractThe rapid advancement of main group III–V nanomaterials endows photodetectors (PDs) with enhanced performance. At present, various III–V nanomaterials are systematically investigated, whereof III–V semiconductors have attracted a successively increased attention that calls for a comprehensive summary which also can define the state‐of‐art for their further development. Herein, this work systematically introduces and discusses key aspects of the field. First, the advanced strategies for the preparation of III–V semiconductor materials and the device structures of the subsequent PDs based on these materials, pristine and doped, are addressed. The focus is then turned to their performance under the irradiation of various wavelengths, separately summarizing and comparing the photodetection properties under infrared, UV and visible light. Finally, challenges and future perspectives of III–V semiconductor‐based PDs are highlighted. This review enlightens the development of III–V semiconductor‐based PDs, and their extended applications for optoelectronic devices in general.

Emerging Advanced Photo‐Rechargeable Batteries

AbstractThe depletion of fossil fuels necessitates the efficient utilization of solar energy and the urgent resolution of its instability, intermittency, and storage challenges. Photo‐rechargeable batteries, which integrate solar cells and energy storage batteries to convert solar energy into electricity and store it as chemical energy, have gradually emerged as a novel research direction to meet the energy demands of various standalone applications such as building facades, mobile transportation devices, and outdoor settings. This review elucidates the device structure, working principles, and key parameters of photo‐rechargeable batteries. Furthermore, various photo‐rechargeable battery systems such as lithium‐ion battery, lithium‐sulfur battery, sodium‐ion battery, zinc‐ion battery, and aluminum‐ion battery are categorized and summarized, detailing their composition, operational mechanisms, and photoelectric performance. Finally, the future research directions of photo‐rechargeable batteries are delineated, advocating for the exploration of dual‐functional materials that integrate light conversion and energy storage. Specifically, emphasis is placed on studying the compatibility between optical and energy storage materials, investigating new battery operation mechanisms under illumination conditions, considering the imperative of achieving high stability and overall efficiency to enhance device performance, and elucidating the future application pathways of these technologies.

A one-step fabrication method of flexible magnetostrictive fiber ribbon based on Fe50Co50 alloy and its characteristics study

Magnetostrictive materials are widely used in sensors, actuators and micro-nano electronics because of their excellent performance. However, traditional rigid magnetostrictive materials are difficult to adapt to the flexible and deformable structure of flexible electronic devices. In order to solve the deformation, sensing and control problems in the field of flexible electronics, a one-step new method of is proposed to deposit Fe50Co50 fiber ribbons with reciprocated and loop structures on flexible substrate. Helmholtz coil is designed to test the magnetostrictive positive effect ability of Fe50Co50 ribbon, and its magnetostrictive strain curve is analyzed. Furthermore, frequency domain characteristics of Fe50Co50 ribbon are tested, and the influence of externally driving magnetic field on elastic layer materials and resonance output characteristics is analyzed. The experimental results show that Fe50Co50 ribbon exhibits good low-frequency magnetic field characteristics. And free end displacement of Fe50Co50 ribbon based on loop structure, under 12 mT alternating magnetic field and 134 mT bias magnetic field, reaches a peak-to-peak value of 870 μm for first-order resonance, and 320 μm for second-order resonance. This verifies that Fe50Co50 ribbon possesses the expected properties that magnetostrictive materials should have, and innovatively breaks through the technical bottleneck of manufacturing flexible micro-nano magnetostrictive energy exchange components.

Enhanced performance of ambient-air processed CsPbBr3 perovskite light-emitting electrochemical cells via synergistic incorporation of dual additives

Metal halide perovskite light-emitting electrochemical cells (MHP-LECs) are promising due to their facile solution processability and exceptional optoelectrical properties. However, commercialization is hindered by poor thin-film coverage and the need for glovebox processing. This study addresses these issues by incorporating poly(ethylene oxide) (PEO) and potassium hexafluorophosphate (KPF6) into cesium lead bromide perovskite (CsPbBr3) emitting layers (EML), processed under ambient-air conditions. These perovskite composite thin films were spin-coated on a preheated substrate, and the device structure was ITO/PEDOT:PSS/EML/Al. Notably, the MHP-LEC based on CsPbBr3:PEO:KPF6 (100:65:0.2, weight ratio) exhibited pure-green emission with a peak at 524 nm and a narrow full width at half-maximum of 27 nm. Compared to a reference device (CsPbBr3:PEO (100:65, weight ratio)), the new device showed 1.5-, 4-, and 5-fold improvements in current density, electroluminescence (EL) intensity, and lifetime, respectively. These enhancements are attributed to reduced non-radiative current leakage, improved film surface coverage and passivation, and balanced charge carrier injection and transportation. This study offers a straightforward approach for processing CsPbBr3 thin films under ambient-air conditions, enhancing the EL performance of MHP-LECs.

Suppressing harmful defects to enhance the performance of kesterite solar cells via extra Mg-doping

Extra-cations doping is known to be an effective approach to control the generation of harmful defects and band-tail states in Cu2ZnSn(S, Se)4 (CZTSSe) solar cells. Here, Mg is used as the extra doped element candidate, the impact of its doping concentration on the composition, structure, morphology, electrical properties, and efficiency of CZTSSe devices is systematically investigated, and its optimal doping concentration is 2 %, which can improve the efficiency of devices from 7.08 % to 9.0 %. The remarkably improved efficiency of the extra Mg-incorporated devices can be explained by the better crystalline quality and fewer deep defects. This work can provide a new approach to boost the performance of kesterite solar cells.

Analysis of Channel Current Noise in Small Nanoscale Metal Oxide Semiconductor Field Effect Transistors.

The shrinkage of metal oxide semiconductor field effect transistor (MOSFET) to the small size of the nanoscale results in changes in their channel current noise composition. This paper determines the channel current noise composition of 90nm MOSFET through experiments, and according to the device material and noise characteristics analysis, the channel current noise of 90nm and below is obtained, which not only contains thermal noise and suppressed channel shot noise, but also adds suppressed gate tunneling shot noise and cross-correlation noise. Then, Monte Carlo simulation of 10nm MOSFET noise is further used to determine the channel current composition of small size nanoscale devices. Subsequently, based on the device structure and fundamental characteristics of channel current noise, the channel current noise model is established. Finally, this model is employed to analyze the relationship between thermal noise, suppressed shot noise, cross-correlation noise, and channel current noise in relation to bias parameters and device characteristics. The theoretical results are basically consistent with the experimental and the simulated results, and the channel noise increases with the increase of bias voltage. This achievement holds promise for enhancing the operational efficiency, reliability, and lifetime of nanoscale small-sized MOSFET devices.

Numerical simulation of all inorganic CsPbIBr2 perovskite solar cells with diverse charge transport layers using DFT and SCAPS-1D frameworks

All inorganic CsPbX3 perovskites (X = Br and I) are excellent candidates for stable and efficient perovskite solar cells (PSCs). Among them, CsPbIBr2 demonstrated the most balanced characteristics in terms of band gap and stability. Nevertheless, the power conversion efficiency (PCE) of CsPbIBr2-based solar cells is still far from that of Hybrid PSCs, and more research is required in this aspect. Herein, DFT and SCAPS-1D frameworks are employed to explore the optimized device configurations of CsPbIBr2 PSCs. DFT is used to explore the structural and optoelectronic characteristics of CsPbIBr2, while SCAPS-1D is employed to examine various device structures of CsPbIBr2-based PSCs. The band structure demonstrated the direct band gap nature of CsPbIBr2 with a band gap of 2.12 eV. Moreover, we have used TiO2, SnO2, ZnO, WS2, IGZO, CeO2, In2S3, and CdS as ETLs, and Cu2O, CuI, MoO3, NiO, CuSCN, CuSbS2, CBTS, CFTS, and CuO as HTLs for identifying the best ETL/CsPbIBr2/HTL configurations. Among 72 device combinations, eight sets of PSCs are identified as the most efficient configurations. In addition, the influence of various parameters like the thickness of various layers, doping concentration, perovskite defect density, ETLs and interfaces, series resistances, shunt resistances, and temperature on device performance have been comprehensively studied. The results demonstrate Cu2O as the best HTL for CsPbIBr2 with each ETL, and PSC with device structure ITO/WS2/CsPbIBr2/Cu2O/C exhibited the highest PCE of 16.53%. This comprehensive investigation will provide new path for the development of highly efficient all-inorganic CsPbIBr2 solar cells.

Experimental investigation of high-speed WDM-visible light communication using blue, green, and red InGaN µLEDs.

Micro-light-emitting diodes (µLEDs) hold significant promise for applications in displays and visible light communication (VLC). This study substantiates the viability of a wavelength division multiplexing (WDM)-VLC system using InGaN blue, green, and red µLED devices. The devices exhibited notable color stability and high modulation bandwidth due to the weakly polarized electric field in the blue and green semipolar devices and the stress-optimized structure in the red device. The aggregated data rate reached 11.14 Gbps. Moreover, the blue, green, and red InGaN µLEDs exhibited a wide color gamut, encompassing 119.4% of the NTSC and 89.2% of the Rec. 2020 standards, affirming the potential of blue, green, and red InGaN µLEDs for applications in full-color display and WDM-VLC systems.

CFD design and testing of an air flow distribution device for microwave infrared hot-air rolling-bed dryer

In this study, a new microwave infrared hot air rolling bed dryer (MIHRBD) was developed and computational fluid dynamics (CFD) techniques were introduced into the design process of the integrated drying system. The structure of the air distribution device was optimised to improve the airflow uniformity over the curved surface of the rolling bed in the microwave-hot air drying combined equipment. The research findings reveal that, across eleven models, the outlet airflow velocity stabilises once the number of mesh elements reaches 5 million, achieving significant computational accuracy at that point. Optimizing components like the uniform air distribution pipe, turbulence plates, and wind deflectors significantly enhanced airflow distribution uniformity by 52.1%. The best airflow and temperature distribution uniformity on the rolling bed surface was achieved when the inlet airflow velocity ranged from 1 to 3 m s−1, with minimum Vd, Uv and temperature non-uniformity coefficients of 0.007 m s−1, 7.2% and 0.2%, respectively. Validation tests on the MIHRBD pilot equipment showed that after optimizing the uniform air distribution device, the minimum temperature difference on the pleurotus eryngii surface was 3.1 °C. This confirmed the feasibility of the computational fluid dynamics method. Introducing hot air significantly enhanced pleurotus eryngii's drying uniformity, with the Page model effectively predicting the MIHRBD drying process. This study provides technical support for future developments in this field of equipment manufacturing and drying process analysis.

Study on the regulation factors and mechanism of self-heating effects in non-rectangular 14 nm bulk FinFET*

Abstract This work investigates the innovative design of a 14 nm bulk 3D non-rectangular structure fin field-effect transistor (FinFET). By incorporating a cylindrical trapezoidal structure into the upper portion of the FinFET, it transcend the limitations posed by the self-heating (SH) effect observed in traditional rectangular fins.Through the density gradient model and thermal conduction model, the changes in the electron carrier temperature and lattice temperature of the channel are studied, and the relationship between electrical properties and thermal resistance was further analyzed, revealing the effect of SH on the threshold voltage and switching speed of the device. In addition, the SH effect of the doping of source and drain extension regions was also explored, and the effects of electron mobility changes at different ambient temperatures were also studied to clarify their impact on the electrical properties. Ultimately, this work offers novel insights into the design, optimization, and reliability studies of device structures affected by SH effects.

Phonon-assisted leakage current of InGaN light emitting diode

We report on the leakage current mechanism in a blue GaN-based light-emitting diode (LED). The device structure was grown by the MOCVD technique on a sapphire substrate. The LED was characterized through various measurements including current-voltage, electroluminescence, and secondary ion mass spectroscopy (SIMS). Capacitance-voltage measurements were employed to calculate the depletion layer thickness at different bias voltages and to analyze the doping profile in the active layer. The reverse temperature-dependent current-voltage measurements were carried out to study the leakage mechanism. The leakage current was explained by phonon-assisted tunneling of charge carriers through deep trap states. The trap energy and density of states were extracted from the application of the introduced model. Cathodoluminescence measurements were performed to evaluate the density of dislocations, which were then compared to x-ray diffraction measurements. The determined value was close to the density of states obtained from the tunneling model.

Multi-objective optimization and inverse design of complementary field-effect transistor using combined approach of machine learning and non-dominated sorting genetic algorithms for next-generation semiconductor devices

Complementary field-effect transistors (CFETs), which are structures in which different types of transistors are vertically stacked with a shared control gate, are being focused on for continuing to satisfy Moore's law by overcoming the limitations in pitch scaling. The structures of semiconductor devices become more complex as technology node shrinks, and interrelated multivariate parameters increase. In addition, predicting problems and proposing solutions by identifying complex patterns within extensive data collected for emerging semiconductor designs pose significant computational challenges and are inherently difficult. As a breakthrough in design technology co-optimization for advanced devices, this study developed a novel optimization framework integrating technology computer-aided design simulations, machine learning, and non-dominated sorting genetic algorithms. The developed framework provides unbiased optimal solutions, even in a high-dimensional objective space, while considering the tradeoff relationships between multiple variables. In addition, it enables inverse design to identify the design parameters of devices that satisfy specific electrical performance criteria using only a forward model, while achieving an error rate of less than 2%. Using this framework, we analyzed the operational mechanism of CFETs by comparing the inverse designs of various devices. This novel approach is particularly important when the design space is complex and extensive and is well suited for developing devices that emerge with technological advancements in the semiconductor industry.

Improving the efficiency and stability of betavoltaic batteries based on understanding efficiency fluctuations and gaps with theoretical limits

Wide-bandgap semiconductors are regarded as preferred materials for preparing semiconductor conversion devices in betavoltaic batteries due to their high theoretical conversion efficiency (ηc). However, there are a few comprehensive analytical studies on why the experimental values of ηc are generally much lower than the theoretical limit of ηc (ηc-limit) and how to improve ηc and its stability. In this work, combined with the energy deposition distributions of Ti3H2, 63Ni, and 147Pm2O3 radioactive sources in SiC obtained from Monte Carlo simulations, a multi-physical mechanism, multi-parameter coupling numerical model was established. This model can comprehensively analyze the output characteristics of betavoltaic batteries under the influence of actual device structural and material parameter changes. Our results show that changes in structural and material parameters cause significant variations in the collection efficiency (Q) of the radiation-generated electron–hole pair (RG-EHP). Considering structural parameters are easy to control, instabilities in actual SiC material parameters, which include electron diffusion length (Ln), hole diffusion length (Lp), and surface recombination velocity (S), are the main reason that ηc fluctuates significantly and is generally far lower than ηc-limit. Due to differences in the distribution of RG-EHP produced by different radioactive sources in SiC, the dominant parameters causing ηc fluctuations differ. By analyzing differences in recombination loss mechanisms under different radioactive sources, the device structures were designed in a targeted manner to make ηc closer to ηc-limit. Meanwhile, when the SiC material quality fluctuates, the stability of ηc increases by 58.5%, 35.3%, and 48.2% under Ti3H2, 63Ni, and 147Pm2O3, respectively.

(Invited) Designer 2D Materials and Machine-Learning Assisted Characterization

2D materials offer enormous opportunities to build designer structures with widely tunable properties. The precise atomic engineering and quick characterization approach are critical to advance the application of designer 2D materials. This talk will introduce new optical features of designer 2D materials [1-4] with a focus on atomic substitution in monolayer WS2 [1]. The engineering of 2D materials presents unique opportunities for optoelectronic device and quantum information platform. When designing optoelectronic devices of 2D materials, spectroscopic permittivity of 2D material is a key parameter. While ellipsometry has been used to measure permittivity, it requires simple device structure, non-trivial parameter fitting, and special setup. This talk will also present a new machine-learning assisted approach to measure permittivity of 2D materials embedded in complex device structures without model fitting, which can facilitate a quick, accurate, and in-situ characterization of 2D and other thin film materials [5].