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The aim of this study was to evaluate the hypotensive effect and optimal protocol of inspiratory muscle resistance training (IMST). Randomized controlled trials using IMST to lower blood pressure (BP) were retrieved from 12 databases as of July 2022. A meta‐analysis of BP and heart rate variability (HRV) was performed and a trial sequence analysis was performed using trial sequential analysis (TSA) software. Twelve articles (n = 386 participants) from five countries were included, with a mean quality score of 5.83. IMST achieved significant results in reducing systolic, diastolic, and mean arterial pressure (−7.93 [−12.08, −3.78]; −3.80 [−6.08, −1.53]; −4.90 [−13.76, 3.96]). Furthermore, TSA has shown that the findings for systolic and diastolic BP are conclusive. Finally, considerable variation remained between studies when analyzing HRV. The overall hypotensive effect of IMST was demonstrated by the TSA and was well tolerated in different populations. Of these, two interventions, high resistance or low resistance combined with slow breathing, showed the best efficacy under an 8‐week exercise intervention. In addition, the process of lowering BP by modulating sympathetic vagal activity has not been further confirmed in this study. Future long‐term interventions, especially those over 3 months, are needed to observe the prolonged antihypertensive effects and modulatory mechanisms; controlling for variables such as respiratory rate and executing more rigorous studies to further explore antihypertensive options. [ABSTRACT FROM AUTHOR]

Î"-gate has been used to increase the breakdown voltage of radio frequency (RF) devices, and the damage caused by gate pin etching has been studied. In this study, a TiO2 layer, acting as a protective layer, was inserted between the AlGaN barrier layer and SiN passivation layer. The AlGaN/GaN high-electron-mobility transistor (HEMT) with TiO2 had no kink effect in its output characteristic, and at high gate voltages, it demonstrated a higher transconductance than the HEMT without TiO2. The HEMT without TiO2 exhibited a more prominent saturation tendency for drain current. Additionally, the Câ€"V test data show that the trap state density of the AlGaN/GaN interface of an AlGaN/GaN HEMT with TiO2 decreased compared with a HEMT without TiO2. DC and Câ€"V test results show that the TiO2 layer can effectively reduce the etching damage of the material under the gate. [ABSTRACT FROM AUTHOR]

A metal–insulator–semiconductor high‐electron‐mobility transistor (MIS‐HEMT) with Al2O3/SiNx (SiNx next to semiconductor) double insulators is proposed to obtain lower gate leakage and lower current collapse simultaneously and is comparatively studied in this article. SiNx directly next to the (Al)GaN induces fewer interface traps and provides better passivation, and Al2O3 can greatly reduce gate leakage. The Schottky gate HEMT and MIS‐HEMTs with single SiNx and Al2O3 layer are also fabricated for comparison. The proposed structure shows the lowest gate leakage and the lowest current collapse as well as better output, transfer, breakdown performance. Besides, this proposed structure shows low requirements on fabrication techniques and induces fewer interface traps. Moreover, to further explore the reason behind those superior performances, the gate leakage mechanisms under reverse and forward bias conditions are studied and the interface traps are compared through capacitance–voltage (C–V) measurements in those four kinds of devices. The experimental results demonstrate that the MIS‐HEMT with Al2O3/SiNx double insulators is a superior candidate for nitrides‐based MIS‐HEMT devices. [ABSTRACT FROM AUTHOR]

This article aims to further test the cognitive claims of the so-called subjectivity account of causal events and their linguistic markers, causal connectives. We took Mandarin Chinese, a language that is typologically completely different from the usual western languages, as a case to provide evidence for this subjectivity account. Complementary to the commonly used corpora analyses, we employed crowdsourcing to tap native speakers' intuitions about causal coherence, focusing on four result connectives kějiàn 'therefore', suǒyǐ 'so', yīncǐ 'so/for this reason' and yúshì 'thereupon/as a result'. The analysis shows systematic differences regarding the use of connectives in relations that differ in terms of subjectivity, demonstrating that native speakers make use of subjectivity to encode and decode different types of causal relations in discourse. Moreover, our study evidences that a comprehensive model of subjectivity should include the epistemic dimension of certainty about the subjectivity scale that might be indicated by other linguistic elements. In-depth analyses of the test items revealed that the presence/absence of modality words in the result segments are related to different preferential patterns for the connectives. There is a trade-off between the epistemic dimension of certainty and the expression of subjectivity in the four connectives involved. [ABSTRACT FROM AUTHOR]

This article proposes a parallel dual‐metal‐gate structure (PDM) of AlGaN/GaN high‐electron‐mobility transistors (HEMTs) for high‐linearity applications. Cancellation of the third‐order derivative of the Ids–Vgs curve (gm″)is achieved by splitting the device into two subcells in parallel with different gate metals. The two subcells have different threshold voltages. When the same bias voltage Vgs is applied, the operating states of the two subcells are independently controlled by the gate bias voltages. The maximum transconductance (gm,peak) of the conventional single‐metal‐gate (SMG) HEMT, double‐metal‐gate (DMG) HEMT, and PDM‐HEMT is all comparable, whereas gm″ of the proposed structure is 75% lower than that of the SMG HEMT and 47.8% lower than that of the DMG HEMT. The effects of the differences and width ratios of the work function on gm″ are studied and compared, and a suitably designed PDM‐HEMT that can considerably improve linearity without degrading other performance aspects is obtained. This research has significant implications for high‐linearity applications. [ABSTRACT FROM AUTHOR]

In this study, we analyze the meaning and use of Mandarin causal connectives kějiàn 'therefore/it can be seen that', suǒyǐ 'so', yīncǐ 'for this reason', and yúshì 'thereupon/as a result' in terms of causality and subjectivity. We adopt an integrated approach to subjectivity and analyze the subjectivity profile of a causal construction in terms of three features: the propositional attitude of the consequent, the identity of the subject of consciousness (SoC), and the linguistic realization of the SoC. The investigation is based on natural discourse produced in fundamentally distinctive channels, namely, spontaneous conversation, microblogging, and formal writing. Compared to previous studies, the empirical foundation is therefore enlarged and more varied. The results show that these connectives differ systematically from each other with regard to the above three features, and that the differences remain robust across the three discourse types. The relative importance of each feature in characterizing the connectives is also determined. The propositional attitude appears to be the most important subjectivity feature, followed by the linguistic realization of the SoC and the identity of the SoC. [ABSTRACT FROM AUTHOR]

In this study, AlGaN/GaN high-electron-mobility transistors (HEMTs) were grown on a GaN template and GaN substrate under the same growth conditions. It was observed that, in the HEMT structure grown on the GaN substrate, mobility decreased because of an increase in the two-dimensional electron-gas (2DEG) density; the origin of these redundant electrons was studied. The 2DEG density decreased with decreasing temperature, this phenomenon closely related to unintentionally induced shallow donors with ionization energy calculated to be around 67.8 meV. After Ⅴ/Ⅲ ratio regulation, the 2DEG density returned to a normal level; this combined with photoluminescence, confirmed for the first time that the abnormal increase of 2DEG density in HEMT structure grown on the GaN substrate is associated with nitrogen vacancies. Therefore, increasing the Ⅴ/Ⅲ ratio is beneficial for obtaining higher mobility by returning the 2DEG density to a normal level. [ABSTRACT FROM AUTHOR]

This is a theoretical study of GaN-based heterostructures with unintentionally doped (UID) GaN channel layer and high-resistivity (HR) GaN buffer layer doped by deep acceptors. Self-consistent Schrödinger-Poisson (SP) numerical simulation shows that, by increasing the acceptor concentration in the HR buffer or narrowing the width of UID channel, the quantum confinement of two-dimensional electron gas (2DEG) is enhanced, while the sheet density of 2DEG is reduced. The tuning effect of 2DEG density is attributed to the depletion effect of negative space charges composed of ionized acceptors located in the region between the UID channel and the Fermi-level pinned region in the HR buffer. For the heterostructure without the UID channel, the 2DEG can be depleted as the acceptor concentration is beyond a critical value. However, by inserting a UID channel layer, the depletion effect of buffer acceptor on 2DEG density is reduced. To gain a further insight into the physics, a simple analytical model is developed, which reproduces well the results of SP simulation. By comparing our theoretical results with the experimental ones, a good agreement is reached, thus the validity of our model is verified. [ABSTRACT FROM AUTHOR]

A normally-off hybrid-gate p-GaN high-electron-mobility transistor (HEMT) is presented in this paper. The gate region is designed as a parallel connection between the Schottky-gate and the metal–insulator–semiconductor gate by inserting a dielectric layer under part of the gate metal. Compared to the conventional Schottky-gate p-GaN HEMT, the fabricated hybrid-gate p-GaN HEMT showed a higher threshold voltage of 3.2 V (increases by 167%), and the maximum transconductance is only a slight decrease (reduces by 23%). At the same time, the forward gate leakage current of the hybrid-gate structure is smaller. Furthermore, through simulation, we revealed that the increase in the threshold voltage originated from the delayed full opening of the two-dimensional electron gas. And we also find that the parameters of the gate dielectric layer have a great influence on the performance of the device. The results show that the hybrid-gate structure is a more promising device structure. [ABSTRACT FROM AUTHOR]

In this paper, a study is presented of the effect of Fe in the buffer layer on the laser lift-off (LLO) of GaN high electron mobility transistors (HEMTs). AlGaN/GaN HEMTs grown on Fe-doped and unintentionally doped buffer layers were separated from sapphire substrates using a 248 nm KrF excimer laser lift-off system. We analyzed the variations of the crystal characteristics, two-dimensional electron gas (2DEG) characteristics and the strain state of AlGaN/GaN HEMT films before and after LLO by the x-ray diffraction, Hall and Raman methods. The measurement of the distribution of elemental Fe in the GaN buffer layer was performed by secondary ion mass spectroscopy. The results show that a peak Fe concentration of 9.56 × 1018 cm−3 appears at the interface. Moreover, the crystal quality and 2DEG characteristics of the Fe-doped GaN film obviously degenerated, with the formation of micro-cracks under the threshold laser separation energy density (Es). In this case, the threshold laser damage energy density (ED) was used to measure the laser damage tolerance of GaN in LLO. The analysis considers that additional laser absorption centers, induced by the Fe impurity energy level, coupled with a large residual stress of up to 1.0763 GPa in Fe-doped GaN, reduced the threshold laser damage energy density (ED). [ABSTRACT FROM AUTHOR]

Silicon carbide MOSFET has been commercialized for many years. Its performance is still improving especially for high-frequency application. High-frequency figure-of-merit (HF-FOM) RON* CGD and RON* QGD were used for a comprehensive evaluation of the performance of MOSFET. In this article, SiC planar MOSFETs with different p-body designs were comparatively studied. A new planar MOSFET with buffered gate and thick central oxide gate structure (TCOX-MOS) was proposed to further improve the gate oxide electric field in OFF-state and HF-FOM. Compare to the conventional planar MOSFET (C-MOS), the maximum gate oxide electric field, gate–drain charge, and HF-FOM (RON* QGD) of TCOX-MOS are 32%, 83%, and 84% lower, respectively. Furthermore, TCOX-MOS shows less short-channel effects by better channel shielding structure. The results show that TCOX-MOS is a more attractive device structure. [ABSTRACT FROM AUTHOR]

The temperature uniformity and heating efficiency in a high-temperature epitaxial growth system were investigated by modeling and simulating. The finite element method (FEM) was used to calculate the distribution of magnetic field and temperature field in the reactor of growth system. The simulation results showed that due to the skin effect and heat conduction in the conventional susceptor, the temperature distribution of the wafer on the susceptor is not uniform. However, the temperature uniformity of the wafer can be greatly improved by adding an air gap below the wafer. The existence of air gap effectively reduced the temperature on the center of the wafer, and the effect of its radius on temperature uniformity was studied. By calculating different frequencies and coil currents, the temperature and heating rate in the reactor with modified susceptor were investigated. The results indicated that higher temperature and faster heating rate can be obtained by increasing heating frequency and coil current. However, both lower and higher frequency will bring worse temperature uniformity. [ABSTRACT FROM AUTHOR]

In this paper, AlGaN/GaN- and GaN/AlGaN/GaN-based Schottky barrier diodes (SBDs) were fabricated and studied for comparison. The recorded electrical characteristics of the devices show that the introduction of a GaN cap layer can evidently reduce the reverse leakage current and suppress the forward current decay of the devices. What is more important, the GaN/AlGaN/GaN-based SBDs are capable of greatly alleviating the unrecoverable degradation of the reverse characteristics, which was observed in the device without a GaN cap layer when the device was under long time reverse dc stress. Detailed analyses were discussed. [ABSTRACT FROM AUTHOR]

AlGaN layers were grown on InAlN/AlN/GaN heterostructure with various temperatures. The two-dimensional electron gas density and mobility in heterostructure with high temperature AlGaN were deteriorated which is attributed to the reverse polarization field of AlGaN and the degradation of InAlN structural quality and surface morphology. A 2 nm low temperature GaN spacer was inserted to reduce the risk of InAlN degradation. The improved structures demonstrated an increase of two-dimensional electron gas density and mobility compared to the heterostructures without the GaN spacer, which results in the reduction of sheet resistance. Particularly, at 855 °C, an enhancement of mobility in the improved structure indicates that the heterostructure is relatively stable at this temperature. At higher temperature of 920 °C, significant increase of sheet resistance indicates a sharp degradation of InAlN quality. [ABSTRACT FROM AUTHOR]