Electron Blocking Research Articles

Design of electron blocking layer and its influence on the radial hole transport in GaN-based vertical cavity surface emitting laser diodes

Design of electron blocking layer and its influence on the radial hole transport in GaN-based vertical cavity surface emitting laser diodes

Structure Design of UVA VCSEL for High Wall Plug Efficiency and Low Threshold Current

Vertical-cavity surface emitting lasers in UVA band (UVA VCSELs) operating at a central wavelength of 395 nm are designed by employing PICS3D(2021) software. The simulation results indicate that the thickness of the InGaN quantum well and GaN barrier layers affect the emission efficiency of UVA VCSELs greatly, suggesting an optimal thicknesses of 2.2 nm for the well layer and 2.7 nm for the barrier layer. Additionally, an overall consideration of threshold current, series resistance, photoelectric conversion efficiency, and optical output power results in the optimized thickness of the ITO current spreading layer, ~20 nm. Furthermore, by employing a five-pair Al0.15Ga0.85N/GaN multi-quantum barrier electron blocking layer (EBL) instead of a single Al0.2Ga0.8N EBL, the device shows a ~51% enhancement in the optical output power and a ~48% reduction in the threshold current. The number of distributed Bragg reflector (DBR) pairs also plays crucial roles in the device’s photoelectric performance. The device designed in this study demonstrates a minimum lasing threshold of 1.16 mA and achieves a maximum wall plug efficiency of approximately 5%, outperforming other similar studies.

Enhanced performance of GaN based VCSELs through graded electron-blocking layer design

Electron leakage from the active region to the p-type region restricts the performance of GaN-based Vertical-Cavity Surface-Emitting Lasers (VCSELs). AlGaN EBL can decrease the leakage current, but also raises the hole injection barrier and reduce the hole injection efficiency. Then, it is important to design EBL structures that can enhance both electron blocking and hole injection. In this study, VCSEL devices with three different EBL, basic structure Al0.6Ga0.4N EBL labeled as Device A, newly proposed 16 nm thick Al0.75–0.80Ga0.25–0.20N EBL labeled as Device B, and 18 nm thick Al0.75–0.80Ga0.25–0.20N EBL labeled as Device C, respectively, are designed and analyzed using PICS 3D simulation. Device A represents a basic VCSEL structure, while Device C incorporates a graded electron-blocking layer (EBL) with adjusted thickness. Through simulation results, it is observed that the introduction of a graded EBL in Device C leads to significant performance enhancements compared to the basic structure of Device A. Specifically, the graded EBL effectively reduces band bending and increases the electron barrier height, thereby improving carrier confinement and reducing electron leakage. Additionally, the utilize of a Graded structure in Device C aids in strain relief at the layout between the QB and EBL, resulting in improved electron-blocking capability and potentially enhanced hole transport characteristics. These findings underscore the importance of EBL grading in optimizing the performance of VCSELs, highlighting its potential for advancing the efficiency and functionality of these semiconductor devices. Power of the device C is being improved upto 4.16%, similarly the conduction band barrier height is improved upto 26.6% which is beneficial for better VCSEL performance as it enhances electron confinement in the active region, leading to increased efficiency and reduced carrier leakage and valance band barrier height decreases upto 6.52% and threshold current is decreased upto 4.8% so if valence band barrier height decrease the hole injection efficiency increases and if threshold current decreases the emitting power of the device increase.

Improving photoelectric characteristics of GaN-based green laser diodes by inserting electron blocking layer with gradient Al composition

This paper proposes four new gradient composition electron blocking layer (EBL) structures to enhance the photoelectric performance of GaN-based green laser diodes (LDs). The optical and electrical properties of new structure LDs are theoretically analyzed by LASTIP. It is observed that the implementation of a gradient composition EBL structure increases the effective barrier height for electrons, thereby better inhibiting the electron current overflow from the active region. In addition, the optical field leakage is effectively suppressed, lower threshold current and higher output power are obtained. The four different new structures have obvious differences in the improvement of the hole current injection and slope efficiency of multiple quantum well (MQW) LDs, and the underlying reasons for these phenomena are explored. Simulation results indicate that adopting a gradually descending Al component EBL structure yields optimal improvements in the photoelectric performance of LDs.

Design And Implementation of Blockchain-Based Security Solutions for Electronic Health Records (EHRS): Enhancing Data Integrity and Privacy

A block chain-based electronic health record (EHR) system is the primary focus of this study. To improve data security and interoperability, healthcare is increasingly looking to cloud-based electronic health record (EHR) systems and block chain technology. It delves into the topic of choosing the right cloud infrastructure, data management methodologies, and block chain technology to guarantee the availability, integrity, and security of patient data. We go over every detail of the system's design and implementation, from the block chain network and cloud storage layer to the user interface. By comparing it to more conventional EHR systems, the pilot research finds that the new system is more capable of protecting, exchanging, and managing patient data. We take a look at the pros, cons, and obstacles that might prevent a cloud EHR system based on block chain from being widely used. Insights and suggestions from this study address the obstacles, give direction for effective adoption, and are of great value to healthcare organisations thinking about implementing such systems. Keywords: Block chain, Security, Solutions, Electronic Health Records (Ehrs) And Privacy

Polarization-Doped InGaN LEDs and Laser Diodes for Broad Temperature Range Operation.

This work reports on the possibility of sustaining a stable operation of polarization-doped InGaN light emitters over a particularly broad temperature range. We obtained efficient emission from InGaN light-emitting diodes between 20 K and 295 K and from laser diodes between 77 K and 295 K under continuous wave operation. The main part of the p-type layers was fabricated from composition-graded AlGaN. To optimize injection efficiency and improve contact resistance, we introduced thin Mg-doped layers of GaN (subcontact) and AlGaN (electron blocking layer in the case of laser diodes). In the case of LEDs, the optical emission efficiency at low temperatures seems to be limited by electron overshooting through the quantum wells. For laser diodes, a limiting factor is the freeze-out of the magnesium-doped electron blocking layer for temperatures below 160 K. The GaN:Mg subcontact layer works satisfyingly even at the lowest operating temperature (20 K).

Doping bilayer hole-transport polymer strategy stabilizing solution-processed green quantum-dot light-emitting diodes.

Quantum-dot light-emitting diodes (QLEDs) are solution-processed electroluminescence devices with great potential as energy-saving, large-area, and low-cost display and lighting technologies. Ideally, the organic hole-transport layers (HTLs) in QLEDs should simultaneously deliver efficient hole injection and transport, effective electron blocking, and robust electrochemical stability. However, it is still challenging for a single HTL to fulfill all these stringent criteria. Here, we demonstrate a general design of doping-bilayer polymer-HTL architecture for stabilizing high-efficiency QLEDs. We show that the bilayer HTLs combining the electrochemical-stable polymer and the electron-blocking polymer unexpectedly increase the hole injection barrier. We mitigated the problem by p-doping of the underlying sublayer of the bilayer HTLs. Consequently, green QLEDs with an unprecedented maximum luminance of 1,340,000 cd m-2 and a record-long operational lifetime (T95 lifetime at an initial luminance of 1000 cd m-2 is 17,700 hours) were achieved. The universality of the strategy is examined in various polymer-HTL systems, providing a general route toward high-performance solution-processed QLEDs.

(Invited) Breakdown Improvement of Mg-Diffused Current Blocking Layer in Ga2O3

The path towards an all-planar highly efficient vertical Ga2O3 transistor requires the construction of a buried gate barrier junction to circumvent the pre-mature breakdown near the gate often seen in lateral structures. An effective selective doping technique is necessary to achieve this. By taking advantage of the high diffusivity of dopants and defects in Ga2O3, we propose the use of diffusion doping as a rapid and non-invasive technique to explore the possibility of an effective current blocking layer (CBL) in vertical Ga2O3 transistors. Unlike ion implantation, diffusion doping does not require an 1100°C annealing for the repair of crystal damage. Thus, the desired Mg doping profile can be maintained by the end of device fabrication, which is the key to achieving a high blocking voltage with Mg-doped CBL. In addition, diffusion doping can easily form a much deeper dope junction and be very useful for high-voltage and super-junction devices.Recently, we have demonstrated the first Ga2O3 vertical-diffused-barrier field-effect transistor (or VDBFET) utilizing a Mg-diffusion doped CBL with a spin-on-glass source. The transistor exhibited excellent FET behavior with decent saturation, enhancement-mode operation, and an on/off ratio of more than 109. However, the breakdown voltage is measured to be only 72V most likely due to the punch-through of the Mg-diffused CBL. This is likely caused by a lower-than-expected Mg doping rendering an inefficient electron blocking. In addition, SIMS analysis indicated the existence of Mg-H complex that deactivated the Mg. Thus, the effective Mg doping is even lower than its chemical concentration. Here we will discuss a new strategy to resolve this problem and showcase the characteristics of the improved CBL with a higher breakdown. This development paves the way for the development of high-voltage Ga2O3 VDBFETs.

Constructing a three-dimensional continuous grain boundary with lithium ion conductivity and electron blocking property in LLZO to suppress lithium dendrites

Li7La3Zr2O12 (LLZO) stands out as a promising material for solid-state batteries due to its superior performance. However, the lithium dendrite growth in LLZO significantly affects battery performance due to high electronic conduction of LLZO. Herein, amorphous Li3BO3 (ALBO) is introduced into LLZO to construct a three-dimensional continuous grain boundary with lithium ion conductivity and electron-blocking property to suppress lithium dendrites. The symmetric cells of ALBO-LLZO achieved a high critical current density (CCD) of 1.1 mA·cm−2 and cycled stably for 2000 h at 0.3 mA·cm−2. The capacity retention of LFP/1 ALBO-LLZO/Li battery retains 84.6 % after 200 cycles at 0.2 C, room temperature. This research offers a potential solution to enhance the performance of the garnet electrolyte for ASSBs.

Recent Advances in Flexible Temperature Sensors: Materials, Mechanism, Fabrication, and Applications.

Flexible electronics is an emerging and cutting-edge technology which is considered as the building blocks of the next generation micro-nano electronics. Flexible electronics integrate both active and passive functions in devices, driving rapid developments in healthcare, the Internet of Things (IoT), and industrial fields. Among them, flexible temperature sensors, which can be directly attached to human skin or curved surfaces of objects for continuous and stable temperature measurement, have attracted much attention for applications in disease prediction, health monitoring, robotic signal sensing, and curved surface temperature measurement. Preparing flexible temperature sensors with high sensitivity, fast response, wide temperature measurement interval, high flexibility, stretchability, low cost, high reliability, and stability has become a research target. This article reviewed the latest development of flexible temperature sensors and mainly discusses the sensitive materials, working mechanism, preparation process, and the applications of flexible temperature sensors. Finally, conclusions based on the latest developments, and the challenges and prospects for research in this field are presented.

Optimization of the Al Composition of the p‐AlGaN Electron Blocking Layer in GaInN/GaN Multiquantum‐Shell Nanowire LEDs

The aim is to develop highly efficient GaInN/GaN nanowire (NW)‐based light‐emitting diodes (LEDs), which are composed of GaN NWs and multiquantum shell (MQS) active regions. These regions incorporate the polar c‐plane, nonpolar r‐plane, and semipolar m‐plane. A challenge with MQS‐LEDs is that the current path through the c‐plane MQS tends to dominate under low‐current injection conditions. Given that the MQS on the c‐plane is very defective, this injection current is mainly subjected to nonradiative recombination. Therefore, this study explores various optimizations of the p‐AlGaN electron blocking layers (EBLs) to minimize the current injection into the MQS in the c‐plane region. The samples are subsequently grown using a specific process. This involves n‐GaN NWs, GaInN/GaN‐based quantum shells, p‐AlGaN EBLs with different Al compositions, and p‐GaN shells. All these are developed by metal–organic vapor phase epitaxy on an n‐GaN template featuring a SiO2 hole pattern. NW LEDs are fabricated and subsequently their device characteristics are investigated. Under low‐current injection, the sample with a lower Al composition exhibits higher luminescence intensity. However, this trend reverses when the injection current increases. The findings suggest that AI composition and thickness in the p‐AlGaN EBL significantly affect the output power and the emission wavelength.

Wafer-scale CMOS-compatible graphene Josephson field-effect transistors

Electrostatically tunable Josephson field-effect transistors (JoFETs) are one of the most desired building blocks of quantum electronics. Applications of JoFETs range from parametric amplifiers and superconducting qubits to a variety of integrated superconducting circuits. Here, we report on graphene JoFET devices fabricated with wafer-scale complementary metal-oxide-semiconductor (CMOS)-compatible processing based on chemical-vapor-deposited monolayer graphene encapsulated with atomic-layer-deposited Al2O3 gate oxide, lithographically defined top gate, and evaporated superconducting Ti/Al source, drain, and gate contacts. By optimizing the contact resistance down to ∼170 Ω μm, we observe proximity-induced superconductivity in the JoFET channels with different gate lengths of 150–350 nm. The Josephson junction devices show reproducible critical current Ic tunablity with the local top gate. Our JoFETs are in the short diffusive limit with the Ic reaching up to ∼3 µA for a 50 µm channel width. Overall, our demonstration of CMOS-compatible two-dimensional (2D) material-based JoFET fabrication process is an important step toward graphene-based integrated quantum circuits.

High‐Detectivity UV–Visible–NIR Broadband Polymer Photodetector with Polymer Charge Blocking Layer Cross‐Linked by Organic Photocrosslinker

AbstractUltraviolet (UV), visible, and near‐infrared (NIR) broadband organic photodetectors are fabricated by sequential solution‐based thin film coatings of a polymer electron blocking layer (EBL) and a polymer photoactive layer. To avoid damage to a preceding polymer EBL during a subsequent solution‐based film coating of a polymer photoactive layer due to lack of solvent orthogonality, 2‐(((4‐azido‐2,3,5,6‐tetrafluorobenzoyl)oxy)methyl)−2‐ethylpropane‐1,3‐diyl bis(4‐azido‐2,3,5,6‐tetrafluorobenzoate) (FPA‐3F) is used as a novel organic cross‐linking agent activated by UV irradiation with a wavelength of 254 nm. Solution‐processed poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)‐benzidine] (poly‐TPD) films, which are cross‐linked with a FPA‐3F photocrosslinker, are used for a preceding polymer EBL. A ternary blend film composed of PTB7‐Th, COi8DFIC, and PC71BM is used as a NIR‐sensitive organic photoactive layer with strong photosensitivity in multispectral (UV–visible–NIR) wavelengths of 300–1,050 nm. Poly‐TPD films are successfully cross‐linked even with a very small amount of 1 wt% FPA‐3F. Small amounts of FPA‐3F have little detrimental effect on the electrical and optoelectronic properties of the cross‐linked poly‐TPD EBL. Finally, organic NIR photodetectors with a poly‐TPD EBL cross‐linked by the small addition of FPA‐3F (1 wt%) show the detectivity values higher than 1 × 1012 Jones for the entire UV–visible–NIR wavelengths from 300 nm to 1050 nm, and the maximum detectivity values of 1.41 × 1013 Jones and 8.90 × 1012 Jones at the NIR wavelengths of 900 and 1000 nm, respectively.

Effects of Electron Blocking Layer Thickness on the Electrical and Optical Properties of AlGaN-Based Deep-Ultraviolet Light-Emitting Diode

Effects of Electron Blocking Layer Thickness on the Electrical and Optical Properties of AlGaN-Based Deep-Ultraviolet Light-Emitting Diode

P‐25: Tailoring the Threshold Voltage Control of Oxide Thin‐Film Transistor by Controlling Electron Injection using PN Semiconductor Heterojunction Structure

The threshold voltage (VT) is the most important parameter in semiconductor devices. To control the VT of the thin‐film transistors (TFTs), we propose heterojunction structure of p‐type Tellurium (Te) and n‐type Aluminum‐Doped Indium‐Zinc‐Tin‐Oxide (Al:IZTO) which acts as electron blocking layer and carrier transporting layer, respectively. We investigate the effect of adding the heterojunction layer on the Al:IZTO and demonstrate VT shift up to +20V by adjusting the thickness and single / double deposition of the heterojunction Te layer.

P‐251: Late‐News Poster: OLED Lifetime Optimization in Lower Current‐Density Region

The Organic Light Emitting Diode (OLED) lifetime property was investigated in the lower current‐density region. The OLED display is required for an equivalent long lifetime performance in higher and lower current‐density regions. It was clarified that hole accumulation at the interface between electron blocking layer (EBL) and emissive layer (EML) is important for the Blue OLED lifetime property at lower current densities. The device simulation showed that the appropriate EML hole barrier affects the carrier distribution.

Quantum computation of stopping power for inertial fusion target design

Stopping power is the rate at which a material absorbs the kinetic energy of a charged particle passing through it-one of many properties needed over a wide range of thermodynamic conditions in modeling inertial fusion implosions. First-principles stopping calculations are classically challenging because they involve the dynamics of large electronic systems far from equilibrium, with accuracies that are particularly difficult to constrain and assess in the warm-dense conditions preceding ignition. Here, we describe a protocol for using a fault-tolerant quantum computer to calculate stopping power from a first-quantized representation of the electrons and projectile. Our approach builds upon the electronic structure block encodings of Su et al. [PRX Quant. 2, 040332 (2021)], adapting and optimizing those algorithms to estimate observables of interest from the non-Born-Oppenheimer dynamics of multiple particle species at finite temperature. We also work out the constant factors associated with an implementation of a high-order Trotter approach to simulating a grid representation of these systems. Ultimately, we report logical qubit requirements and leading-order Toffoli costs for computing the stopping power of various projectile/target combinations relevant to interpreting and designing inertial fusion experiments. We estimate that scientifically interesting and classically intractable stopping power calculations can be quantum simulated with roughly the same number of logical qubits and about one hundred times more Toffoli gates than is required for state-of-the-art quantum simulations of industrially relevant molecules such as FeMoco or P450.

Exploring an InGaN Micro-LED structure for optimum IQE operating on low current condition through simulation study

Light-emitting diodes (LEDs) are key components in display applications. The quantum efficiency of GaN/InGaN LEDs has been enhanced, leading to advancements in indoor and outdoor RGB LED display applications. White LED backlights are commonly used in displays due to the increased efficiency of InGaN LEDs. Despite efficiency, lifespan and image retention issues, OLED displays are utilized in high-end mobile phones to meet market expectations for screen response time and color saturation. Micro-LED RGB full-color displays have the potential to dominate the next-generation display market, driven by the increasing demands for resolution, power consumption and response time. Micro-LEDs are becoming smaller, reaching sizes of 50[Formula: see text][Formula: see text]m or even smaller, to meet the high-resolution requirements of displays. They offer higher contrast, brightness and faster response speeds. This research utilizes numerical simulations to develop a model for radiative and nonradiative recombination in InGaN semiconductor materials. The aim is to investigate the internal quantum efficiency (IQE) of various chip sizes, quantum well counts, well thicknesses and electron block layers under low current densities. The research reveals that the optimal structure is a single quantum well with an electron block layer (EBL), which can increase IQE from 53.85% to 80.9% at 0.01[Formula: see text]A/cm2 under low current density conditions, with a decrease in the number of quantum wells to one. The IQE efficiency improvement is 27.05%.

Solution‐Processed Efficient Organic Upconversion Device for Direct NIR Imaging

AbstractInfrared upconversion devices (UCDs) enable NIR imaging without array and readout circuits, making them desirable for portable sensor, imaging and monitoring. However, the exorbitant cost and difficulties in fabrication associated with vacuum‐deposited materials, which are usually employed in high‐performance UCDs, restrict their application in flexible‐stretchable systems. Here, a solution‐processed upconversion device (s‐UCD), which is composed of detector and emitter, with high conversion efficiency and low turn‐on voltage achieved by device structure design and interlayer engineering is reported. The role of the electron blocking layer is investigated in s‐UCDs, and a peak luminance of 5,500 cd m−2 @7 V and a luminance on‐off ratio of 110000 @5.25 V are achieved. The s‐UCDs exhibit high resolution, microsecond response time and are compatible with flexible substrates. With the high‐performance large‐area s‐UCDs, direct non‐invasive transmission‐based bioimaging applications with high quality of bioimaging are further performed. It is believed that the s‐UCD imaging system offers potential applications for portable low‐cost non‐invasive tissue analysis, disease diagnosis, and virtual reality.

A light emitting device with TiO2:Er3+/ZnO heterostructure for enhanced near-infrared electroluminescence

Near-infrared (NIR) electroluminescence (EL) devices based on Er3+ ions doped TiO2 emitting layer have been fabricated by employing a facile sol–gel method. The effect of Er3+ ion doping concentration on the EL performance of TiO2:Er3+ thin film devices was investigated. Moreover, a novel device with the core of TiO2:1%Er3+/ZnO heterostructure was designed and fabricated. The EL performance of the device with optimized Er3+ ion doping concentration and improved structure was significantly improved. The NIR EL-enabling voltage of the improved device is as low as ∼5 V. The attenuated concentration quenching effect and the ZnO film as an electron blocking layer should contribute to the improved EL performance of the optimized device.