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Based on the three-temperature 30 V DC stress tests, the reliability of InAlN/GaN heterostructure field-effect transistors (HFETs) on SiC substrate was assessed for the first time. Using a failure criterion defined as 20% reduction in zero-gate-voltage drain current ( I\mathrm {dss} ), the activation energy was estimated to be 1.94 eV, and the median time to failure was estimated to be 8.9\times 10^6 h at junction temperature of 150°. Moreover, the high temperature material storage indicates that the lifetime of InAlN/GaN HFETs can be further prolonged by the optimization of device process, such as introducing LPCVD SiN or ALD Al2O3 as gate dielectric layer. [ABSTRACT FROM AUTHOR]

Presents a high-efficiency and compact AlGaN/GaN heterojunction field-effect transistor (HFET) power amplifier integrated with a microstrip antenna at 7.25 GHz for RF front-end circuit applications. AlGaN/GaN HFET technology; Circuit design and fabrication.

In this paper, we report on a novel enhancement-mode AlGaN/GaN gates-separating groove heterostructure field-effect transistor (GSG HFET), in which a block barrier exists between the double gates as realized by dry etching. The current transport dominated by thermionic emission or thermionic field emission results in a high drain current density. The threshold voltage modulation mechanism of AlGaN/GaN GSG HFET is investigated. Due to the increasing of block barrier height and width, the threshold voltage shifts obviously towards to the positive direction with increasing the gate length or gate-to-gate distance ( L gg ). By optimizing the device structure, a threshold voltage of 1.8 V and a comparable drain current density of 550 mA/mm are obtained at L gg  = 180 nm, while the values of 2.5 V and 370 mA/mm are obtained at L gg  = 280 nm. Moreover, it's noteworthy that the threshold voltage is less sensitive to recess depth and etching time. The devices show high-uniformity threshold voltage within etching time range from 8 to 9 min. [ABSTRACT FROM AUTHOR]

GaN-based heterostructure field-effect-transistors (HFETs) with graded AlGaN barrier, in which the Al mole fraction of Al x Ga 1− x N ranges from 0 to a certain value (e.g. 35%), demonstrated the potential for high-linearity applications. Based on the two-dimensional (2-D) device simulations, in this paper the trapping effects and current collapse in GaN-based HFETs with graded AlGaN barrier are investigated and analyzed. First, both the carrier profile and direct current (DC) characteristics of the device are obtained for calibration of the simulation model, and the simulation results matched the experimental measurement data very well. In addition, the transient responses of GaN-based HFETs with graded AlGaN barrier are simulated to study the trapping behaviors. As the time increases, two rising trends are observed for the transient current, which are caused by the bulk acceptor traps and surface donor traps, respectively. By comparing with the conventional GaN-based HEMT, the results show that the HFET with graded AlGaN barrier has better immunity to the surface traps, leading to smaller current collapse. [ABSTRACT FROM AUTHOR]

AlGaN/GaN polarization-doped field-effect transistors (PolFETs) were fabricated on the graded AlGaN/GaN heterojunctions grown by metal organic chemical vapor deposition, and the trap behaviors were first systemically evaluated by frequency-dependent conductance–voltage characterizations. It was found that there was no obvious effective traps accumulation in the graded AlGaN/GaN heterojunctions of the PolFETs due to the absence of abrupt heterostructure as in the traditional HFETs. The exactly exponential dependence of the trap state time constants on the bias voltage in PolFETs was observed, which was a typical characteristic for interface traps, indicating a multi-heterointerface feature of the PolFETs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Propose nonalloyed Schottky-Source/Drain technology enabling a gate-first InAlN/GaN HEMTs. [•] The Schottky source can reduce source carrier injection and subthreshold leakage. [•] The gate-first InAlN/GaN HEMTs achieves 229% improvement in breakdown voltage. [•] The Schottky-Source/Drain technology is beneficial to device downscaling. [•] This gate-first InAlN/GaN HEMTs show great promise for self-aligned HEMTs. [ABSTRACT FROM AUTHOR]

• LPCVD-SiN/ALD-AlN bilayer served as passivation layer as well as the thermal-oxidation/wet-etching mask. • ALD grown 3 nm SiO 2 prior to LPCVD SiN effectively protect the GaN channel. • Combining SiN/AlN passivation layer with SiN/SiO 2 gate dielectrics in fully-recess normally-off GaN MISFET. The thermal-oxidation/wet-etching gate-recess mask using low-pressure-chemical-vapor-deposition (LPCVD) SiN/atomic-layer-deposition (ALD) AlN combined with high-quality LPCVD-SiN/ALD-SiO 2 gate dielectric has been developed for the fabrication of normally-off GaN MISFETs by the self-terminated gate recess etching technique. The experimental results showed that the SiN/AlN layer could effectively hinder the formation of surface oxide on GaN cap, and ALD grown SiO 2 could effectively protect the GaN channel from high-temperature damages by the following LPCVD. As a result, the fabricated devices exhibit a small on-resistance degradation, 200 mV hysteresis @ V th = 2.4 V, <1 nA/mm gate leakage current and 6 × 108 on/off ratio. [ABSTRACT FROM AUTHOR]

In this work, by taking into account the isotropic piezoelectric property of III-nitrides and the stress distribution in the circular diaphragm, AlGaN/GaN pressure sensor with a specially designed Wheatstone bridge structure is demonstrated. Two pairs of gateless HEMTs are placed at the tensile (near to the edge) and compressive (in the center) stress regions of the circular diaphragm, respectively, to maximize the pressure sensor's responsivity and stability. As a result, the 2DEG resistors located diagonally featured completely opposite piezoelectric polarization effects, which translated to a linear response of the fabricated AlGaN/GaN pressure sensor with a high sensitivity of 72 μV/kPa/V. The device also showed a large output capability of 64.8 mV/V, suggesting a potentially low power consumption in the practical applications. [ABSTRACT FROM AUTHOR]

The excellent electrical properties of graphene make it have broad application in electronic devices [1–2]. Grain boundaries and wrinkles will greatly scatter charge carriers of graphene [3–4]. Graphene with less gain boundaries and wrinkles are highly demanded. At present, the chemical vapor deposition (CVD) of graphene on Cu foil/Cu-Ni surfaces has been known as the simplicity and low cost way to prepare large-sized high-quality graphene films. However, the suppressing nucleation density method also leads to a low growth rate. Here we demonstrate a surface oxygen supply strategy for the Cu Ni substrate on sapphire to form a Cu-Ni-O surface. With the Cu-Ni-O surface, the growth rate of graphene is greatly increased to 240 μm/min. The as-synthesized graphene has less wrinkles, and a small 2D peaks FWHM of 25.2 cm−1. The room temperature sheet resistance reaches 267 Ω/square. This study provides a meaningful method to time-saving synthesis of high-quality graphene. Unlabelled Image • Surface oxygen supply strategy for the Cu Ni substrate on sapphire to form Cu-Ni-O surface. • The high growth rate and high quality of graphene are obtained on Cu-Ni-O surface. • A meaningful method to time-saving synthesis of high-quality graphene. [ABSTRACT FROM AUTHOR]

Understanding the in situ structure, organization, and interactions of macromolecules is essential for elucidating their functions and mechanisms of action. Cellular cryo-electron tomography (cryo-ET) is a cutting-edge technique that reveals in situ molecular-resolution architectures of macromolecules in their lifelike states. It also provides insights into the three-dimensional distribution of macromolecules and their spatial relationships with various subcellular structures. Thus, cellular cryo-ET bridges the gap between structural biology and cell biology. With rapid advancements, this technique achieved substantial improvements in throughput, automation, and resolution. This review presents the fundamental principles and methodologies of cellular cryo-ET, highlighting recent developments in sample preparation, data collection, and image processing. We also discuss emerging trends and potential future directions. As cellular cryo-ET continues to develop, it is set to play an increasingly vital role in structural cell biology., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Based on genetic studies, lysosome dysfunction is thought to play a pathogenetic role in Parkinson's disease (PD). Here we show that VPS13C, a bridge-like lipid transport protein and a PD gene, is a sensor of lysosome stress/damage. Upon lysosome membrane perturbation, VPS13C rapidly relocates from the cytosol to the surface of lysosomes where it tethers their membranes to the ER. This recruitment depends on Rab7 and requires release of a brake, most likely an intramolecular interaction within VPS13C, which hinders access of its VAB domain to lysosome-bound Rab7. While another PD protein, LRRK2, is also recruited to stressed/damaged lysosomes, its recruitment occurs at much later stages and by different mechanisms. Given the putative role of VPS13 proteins in bulk lipid transport, these findings suggest lipid delivery to lysosomes by VPS13C is part of an early response to lysosome damage.

Mutations in Leucine-rich repeat kinase 2 (LRRK2) are responsible for late-onset autosomal dominant Parkinson's disease. LRRK2 has been implicated in a wide range of physiological processes including membrane repair in the endolysosomal system. Here, using cell-free systems, we report that purified LRRK2 directly binds acidic lipid bilayers with a preference for highly curved bilayers. While this binding is nucleotide independent, LRRK2 can also deform low-curvature liposomes into narrow tubules in a guanylnucleotide-dependent but Adenosine 5'-triphosphate-independent way. Moreover, assembly of LRRK2 into scaffolds at the surface of lipid tubules can constrict them. We suggest that an interplay between the membrane remodeling and signaling properties of LRRK2 may be key to its physiological function. LRRK2, via its kinase activity, may achieve its signaling role at sites where membrane remodeling occurs.