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The electrical and optical properties of the carbon doped GaN grown on Si substrate by metal-organic chemical-vapor deposition are investigated. Carbon impurity doping can improve the breakdown voltage effectively. However excess carbon in contrast depresses the breakdown voltage. This result is correlated with the carbon dopant behaviour in GaN which can be observed by analyzing the photoluminescence (PL) spectra. It is explained that the carbon impurity favours the formation of CN (carbon substitution of nitrogen) which acts as a deep level acceptor. The acceptor compensates the n-type background impurities, which may resulting in suppressing the leakage current at high electric field, and leads to the improvement of the breakdown voltage. However, with excess carbon doping level, a significant amount of CGa (carbon substitution of gallium) form in GaN. The CGa, acting as the donor, compensates the CN and hence impairs the concentration of the deep level acceptor. In a result, the compensation of the n-type background impurities by the deep level acceptor is curbed by the CGa-CN self-compensation effect, which leads to the decrease of the breakdown voltage. [ABSTRACT FROM AUTHOR]

The confined and fractional crystallizationbehavior of poly(ethylene oxide)(PEO) in miscible poly(butylene succinate)(PBS)/PEOblends has been investigated. Both nucleation and growth of PEO crystalsthrough the two-step crystallization process were significantly influencedby the morphology of pre-existed PBS spherulites. At the first crystallizationstep, the PEO component as diluents was segregated into differentregions (interlamellar, interfibrillar and interspherulitic) of PBScrystals, which was dependent on the crystal growth rate of PBS andthe diffusion coefficient of PEO. With the increase of crystallizationtemperatures of PBS (Tc,PBS), more and more PEO molecules were excluded out of the lamellastacks of PBS, and the segregations of PEO became larger and larger.Meantime, the connectivity between the adjacent PEO domains was reduceddramatically. At the second crystallization step, PEO crystallizedsubsequently within the existed frameworks of PBS spherulites formedat various Tc,PBS. Onthe one hand, the nucleation rate of PEO was determined by the totalsolid–liquid interfacial area between PBS crystals and PEOdomains, which could significantly reduce the free energy barrierof nucleation embryos. As Tc,PBSincreased, the nucleation rate of PEO decreased with the decreaseof PBS crystal surfaces which were around PEO domains. The fractionalcrystallization of PEO occurred when the nuclei formed at varioussupercoolings. On the other hand, the crystal growth rate of PEO wasmostly influenced by the connectedness between the PEO domains. Withthe increase of Tc,PBS, the continuous phases of PEO were transformed into isolated domains.The crystal growth of PEO decreased gradually, due to the restrictionsto the diffusion of PEO chains. PEO could only nucleate and grow insideeach isolated domains, just forming tiny PEO crystals. It was foundthat the crystallization of PEO was dependent not only on the diffusionlength of PEO, but also on the intrinsic morphological features ofPBS spherulites. [ABSTRACT FROM AUTHOR]

The Tianshan Range--Junggar Basin--Kalamaili Range system represents the southwestern Central Asian Orogenic Belt and is a natural laboratory for studying intracontinental deformation processes. Its current topography is a product of the farfield effects of the Cenozoic India-Asia collision. However, the Mesozoic topographic and tectonic evolution of the Tianshan and Kalamaili Ranges and their impacts on the Junggar Basin remain enigmatic due to the scarcity of data. Here, we present a comprehensive synthesis of sedimentological and geochronological data on these ranges and adjacent basins to reconstruct the intracontinental evolution from the Early Jurassic to the Early Cretaceous. Based on field observations and seismic profile analysis, we identified several unconformities within the late Mesozoic strata in the Tianshan Range and the Junggar Basin. Detrital zircon U-Pb dating results for Lower Jurassic to Lower Cretaceous sandstones of the eastern and southern Junggar Basin, with published paleocurrent data, reveal a complex intracontinental topographic evolution. Moreover, tuffaceous gravels and tuff samples yielded weighted mean zircon 206Pb/238U ages of 156.5 ± 3.2 Ma and 156.3 ± 2.2 Ma, respectively, which indicates the presence of contemporary magmatic activity. The deformation and magmatism mentioned above were possibly related to multi-plate convergence in East Asia during the late Mesozoic. This study provides new insights into the late Mesozoic tectonic-magmatic evolution of the Tianshan Range and its adjacent areas. [ABSTRACT FROM AUTHOR]

Non-filament 3D vertical RRAM (VRRAM) is a promising technology for emerging high-density memory applications. In this Letter, the layer-dependent resistance variability at both low resistance state (LRS) and high resistance state (HRS) is assessed on state-of-the-art 8-layer 3D VRRAMs. 2048 devices are measured with the aid of an FPGA-controlled relay matrix which enables automated switching of devices without changing the cabling. The results show LRS exhibits little layer dependence while both the average and the standard variation of HRS decrease from the top layer to the bottom layer. A qualitative speculation is proposed to explain the observation based on the high-resolution transmission electronic microscope image. This work is beneficial for future 3D VRRAM circuit design and performance improvement. [ABSTRACT FROM AUTHOR]

The pollen wall is important for protecting the male gametophyte and for fertilization. The lipid components of the pollen wall are mainly synthesized and transported from the sporophytic tapetum. Although several factors related to lipid biosynthesis have been characterized, the molecular mechanisms underlying lipid biosynthesis during pollen development in rice (Oryza sativa L.) remain elusive. Here, we showed that mutation in the SWOLLEN TAPETUM AND STERILITY 1 (STS1) gene causes delayed tapetum degradation and aborted pollen wall formation in rice. STS1 encodes an endoplasmic reticulum (ER)-localized protein that contains domain of unknown function (DUF) 726 and exhibits lipase activity. Lipidomic and transcriptomic analyses showed that STS1 is involved in anther lipid homeostasis. Moreover, STS1 interacts with Polyketide Synthase 2 (OsPKS2) and Acyl-CoA Synthetase 12 (OsACOS12), two enzymes crucial in lipidic sporopollenin biosynthesis in pollen wall formation, suggesting a potentially lipidic metabolon for sporopollenin biosynthesis in rice. Collectively, our results indicate that STS1 is an important factor for lipid biosynthesis in reproduction, providing a target for the artificial control of male fertility in hybrid rice breeding and insight into the function of DUF726-containing protein in plants. [ABSTRACT FROM AUTHOR]

Recess structure is one of the main schemes for insulated-gate E-mode GaN transistors. In this work, selective area growth (SAG) is proposed to fabricate damage-free recess-gate device, and related progresses regarding process optimization and structure evolution have been reviewed. Firstly, the SAG process has been optimized by interface separation (conduction interface and regrowth interface) and n-type Si impurity removal to achieve high-quality AlGaN/GaN heterostructure. Compared to the traditional etching method, the feasibility and superiority of SAG scheme are demonstrated for realizing E-mode Al2O3/GaN MISFET with small Vth hysteresis. Then, by inserting an in situ AlN interlayer, the SAG Al2O3/AlN/GaN MISFET yields improved frequency dispersion and gate channel conduction performances. To further enhance the channel conduction, the SAG partially recess-gate Al2O3/AlGaN/GaN MIS-HFET structure is proposed, by which both high Vth and high-field-effect channel mobility have been achieved. Those results indicate that SAG method gives a perspective way for insulated-recess-gate GaN transistors fabrication. [ABSTRACT FROM AUTHOR]

We experimentally investigate the time-dependent degradation of AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors subjected to different bias conditions. By means of the combined performance under OFF/SEMI-ON/ON state bias conditions, the dependence of threshold voltage (Vth), maximum transconductance (gm) and saturation drain current (Idsat) on stress mode are revealed. In the OFF-state, with the high temperature reverse bias stress, the main mechanism is the charge-trapping in the gate dielectric layer, leading to the recoverable negative shift of the Vth. In the SEMI-ON-state, because of the hot-carrier injection, the hot electrons could break the Si–H bonds, resulting in the generation of interface states and can also be captured by the trap states in the AlGaN barrier or GaN buffer. This effect will cause the decrease of saturation drain current and an unrecoverable Vth negative shift. In the ON-state, due to the attenuation of hot electrons effect, Vth hardly changes, while Idsat has a dramatic decrease caused by the self-heating effect. Low frequency noise characteristics were used to extract the defect state density, which then increases by about three orders of magnitude after SEMI-ON-state stress. [ABSTRACT FROM AUTHOR]

In this work, the effects of hydrogen on an AlGaN/GaN metal insulator semiconductor field effect transistor (MISFET) with SiNx gate dielectric were investigated. It is found that after hydrogen exposure, (1) the AlGaN/GaN MISFET exhibits better DC performance with larger maximum transconductance, (2) the gate lag phenomenon is effectively suppressed and (3) the 1/f noise performance is improved with lower noise magnitude. These results are different from previous observations in other III–V semiconductor devices. Based on the theoretical analysis by space charge limited current and low-frequency noise models, we propose that the hydrogen treatment induces hydrogen incorporation into SiNx, which could passivate the defect centers. These findings demonstrate the high hydrogen tolerance of AlGaN/GaN MISFETs. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate an enhanced voltage-blocking ability for GaN-on-Si epitaxial structure with the novel feature of combined Mg-doped-GaN/low-temperature-AlN (LT-AlN) interlayers in the buffer. With an optimized Mg-doping level, such combined interlayers can eliminate the original leakage path at the LT-AlN/GaN interface due to the interfacial roughening effect caused by the Mg doping. As a result, for AlGaN/GaN heterojunction FETs (HFETs) fabricated on such epitaxial structure (template), its off-state leakage current could be reduced by 1–2 orders of magnitude and its breakdown voltage could be remarkably raise to 252%. Although, the Mg-doped-GaN interlayer would cause a little degradation on device on-state performance, such as 6.6% increase of on-resistance, its contribution on improving device’s voltage-blocking ability and reducing its off-state power dissipation outweighs the drawbacks. [ABSTRACT FROM AUTHOR]

The influence of different C-doping locations in a GaN/Si structure with a GaN/AlN superlattice (SL) buffer on the material and electrical properties of GaN/Si was studied. The introduction of C doping can remarkably degrade the crystal quality of the buffer. C-doping of a top GaN buffer can introduce compressive stress into the top GaN due to the size effect, while C-doping in a SL buffer can impair the compressive stress provided from the SL buffer to the top GaN. It is found that introducing high-density carbon into the whole buffer can result in a more strain-balanced GaN/Si system with small deterioration of the 2DEG channel. Furthermore, the whole buffer C-doping method is an effective and easy way to achieve a thin buffer with low leakage current and high breakdown voltage (266 V@1 nA mm−1; 698 V@10 μA mm−1; 912 V@1 mA mm−1). By using the whole-buffer C-doping method, a 2.5 μm-thick AlGaN/GaN HFET with a breakdown voltage higher than 900 V was achieved, and the breakdown voltage per unit buffer thickness can reach 181 V μm−1. [ABSTRACT FROM AUTHOR]

Both the forward and reverse-bias current transport mechanisms of an AlGaN/GaN Schottky barrier diode with a fully recessed Schottky anode (recessed-SBD) are investigated for the first time. A two-dimensional (2D) device simulation gives insight into the electronic transport. The difference between the forward and reverse conduction paths enables the reduction in Von without sacrificing the low reverse leakage current properties. The results of temperature-dependent current–voltage (T–I–V) measurements show that thermionic field emission (TFE) is the dominant current transport mechanism for forward bias. In the reverse-bias region above the pinch-off voltage, two mechanisms codetermine leakage currents, which contain Frenkel–Poole emission from the overlapped planar contact and tunneling from the recessed sidewall contact. Below the pinch-off voltage, the leakage currents are observed to have exponential temperature dependence, which may be consistent with trap-assisted tunneling (TAT). [ABSTRACT FROM AUTHOR]

The effect of AlN/GaN superlattice (SL) buffer on the strain state in a GaN-on-Si(111) system was studied in detail by room-temperature micro-Raman scattering measurement. An abnormal satellite peak attached to a GaN E2 peak was observed, which was verified to stem from the compressively strained GaN in SLs. The results indicate that the strain-sensitive GaN E2 (high) peak in the GaN-on-Si system with AlN/GaN SLs splits into two peaks because the GaN stress state in the top GaN layer is different from that in SLs. The compressive stress in the GaN layer in SLs was introduced by the AlN layer in each SL period because of the lattice mismatch between GaN and AlN, which ultimately counterbalanced the tensile stress in the top GaN during cooling. Such a counterbalance interaction is strongly dependent on the stiffness coefficient of AlN/GaN SLs, which is proportional to the number of periods of SLs and the relative thickness of AlN in SLs. Such two E2 peaks from GaN enable us to monitor the strain state in the GaN-on-Si system with AlN/GaN SLs quantitatively. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) is enabled by the latest developments in smart sensors, communication technologies, and Internet protocols with broad applications. Collecting data from IoT and generating information from these data become tedious tasks in real-life applications when missing data are encountered in datasets. It is of critical importance to deal with the missing data timely for intelligent decision-making. Hence, this survey attempts to provide a structured and comprehensive overview of the research on the imputation of incomplete data in IoT. The article starts by providing an overview of incomplete data based on the architecture of IoT. Then, it discusses the various strategies to handle the missing data, the assumptions used, the computing platform, and the issues related to them. The article also explores the application of imputation in the area of IoT. We encourage researchers and data analysts to use known imputation techniques and discuss various issues and challenges. Finally, potential future directions regarding the method are suggested. We believe this survey will provide a better understanding of the research of incomplete data and serve as a guide for future research. [ABSTRACT FROM AUTHOR]

The element-free Galerkin scaled boundary method (EFG-SBM) based on moving Kriging (MK) interpolation is used to solve steady heat conduction problems with temperature loads on side-faces, in which the circumferential boundary is discretized based on MK interpolation and the element-free Galerkin (EFG) method. As the shape functions constructed from the MK interpolation possess the Kronecker delta interpolation property, the MK shape functions overcome the shortcomings of moving least squares (MLS) approximation which is difficult to impose essential boundary conditions directly and accurately. As a new boundary-type meshless method, EFG-SBM has advantages of the EFG and scaled boundary finite element method (SBFEM). This method inherits the semi-analytical property of SBFEM by introducing the scaled boundary coordinate system, in which the governing differential equations are weakened in the circumferential direction and can be solved analytically in the radial direction. Unlike the traditional SBFEM, the preprocessing and postprocessing processes of EFG-SBM are simplified since only the nodal data structure is required in the circumferential direction. Numerical examples show that the EFG-SBM based on MK interpolation can obtain a higher accuracy than the SBFEM based on Lagrange polynomials. Compared with the finite element method (FEM), this method can better characterize the thermal singularity at the sharp corner and the temperature distribution of the infinite region.

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression posttranscriptionally through silencing or degrading their targets, thus playing important roles in the immune response. However, the role of miRNAs in the host response against infectious bursal disease virus (IBDV) infection is not clear. In this study, we show that the expression of a series of miRNAs was significantly altered in DF-1 cells after IBDV infection. We found that the miRNA gga-miR-130b inhibited IBDV replication via targeting the specific sequence of IBDV segment A and enhanced the expression of beta interferon (IFN-β) by targeting suppressors of cytokine signaling 5 (SOCS5) in host cells. These findings indicate that gga-miR-130b-3p plays a crucial role in host defense against IBDV infection. [ABSTRACT FROM AUTHOR]

Objective: This study aims to evaluate the clinical efficacy of Sun's abdominal acupuncture combined with cognitive behavioral therapy (CBTI) in the treatment of chronic insomnia with anxiety., Methods: A total of 86 patients diagnosed with chronic insomnia and anxiety were selected from October 2022 to September 2023. Patients were divided into two groups: the cognitive therapy group (treated with CBTI alone) and the combined therapy group (treated with Sun's abdominal acupuncture combined with CBTI). Various parameters including insomnia severity (measured by ISI score), sleep quality (assessed by PSQI score), polysomnography (PSG) results (including sleep duration, latency, wake time, and efficiency), cognitive function (MMSE score), anxiety symptoms (HAM-A score), and insomnia efficacy and anxiety efficacy were compared between the two groups., Results: The combined therapy group exhibited significantly lower ISI and PSQI scores compared to the cognitive therapy group (P < .05). PSG results showed increased sleep duration, decreased latency and wake time, and higher sleep efficiency in the combined therapy group (P < .05). Moreover, MMSE and HAM-A scores were significantly lower in the combined therapy group (P < .05). The total effective rate for both insomnia and anxiety efficacy were higher in the combined therapy group compared to the cognitive therapy group (P < .05)., Conclusions: Sun's abdominal acupuncture combined with CBTI demonstrates superior clinical efficacy in the management of chronic insomnia with anxiety. This combined approach not only reduces insomnia severity and improves sleep quality but also enhances cognitive function and reduces anxiety symptoms. Overall, the efficacy of combined therapy surpasses that of CBTI alone, suggesting its potential for widespread clinical adoption and application.