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Investigation of the dielectric properties of cell membranes plays an important role in understanding the biological activities that sustain cellular life and realize cellular functionalities. Herein, the variable dielectric polarization characteristics of cell membranes are reported. In controlling the dielectric polarization of a cell using dielectrophoresis force spectroscopy, different cellular crossover frequencies were observed by modulating both the direction and sweep rate of the frequency. The crossover frequencies were used for the extraction of the variable capacitance, which is involved in the dielectric polarization across the cell membranes. In addition, this variable phenomenon was investigated by examining cells whose membranes were cholesterol-depleted with methyl-β-cyclodextrin, which verified a strong correlation between the variable dielectric polarization characteristics and membrane composition changes. This study presented the dielectric polarization properties in live cells' membranes that can be modified by the regulation of external stimuli and provided a powerful platform to explore cellular membrane dielectric polarization.

Fabrication of normally-off field effect transistors (FETs) possessed uniform turn-on threshold voltage (

Purpose There is still a clinical need to easily evaluate the metastatic status of lymph nodes during breast cancer surgery. We hypothesized that ex vivo shear-wave elastography (SWE) would predict precisely the presence of metastasis in the excised lymph nodes. Methods A total of 63 patients who underwent breast cancer surgery were prospectively enrolled in this study from May 2014 to April 2015. The excised axillary lymph nodes were examined using ex vivo SWE. Metastatic status was confirmed based on the final histopathological diagnosis of the permanent section. Lymph node characteristics and elasticity values measured by ex vivo SWE were assessed for possible association with nodal metastasis. Results A total of 274 lymph nodes, harvested from 63 patients, were examined using ex vivo SWE. The data obtained from 228 of these nodes from 55 patients were included in the analysis. Results showed that 187 lymph nodes (82.0%) were nonmetastatic and 41 lymph nodes (18.0%) were metastatic. There was significant difference between metastatic and nonmetastatic nodes with respect to the mean (45.4 kPa and 17.7 kPa, p

Facioscapulohumeral muscular dystrophy (FSHD) is caused by insufficient epigenetic repression of D4Z4 macrosatellite repeat where DUX4, an FSHD causing gene is embedded. There are two forms of FSHD, FSHD1 with contraction of D4Z4 repeat and FSHD2 with chromatin compaction defects mostly due to SMCHD1 mutation. Previous reports showed DUX4-induced gene expression changes as well as changes in microRNA expression in FSHD muscle cells. However, a genome wide analysis of small noncoding RNAs that might be regulated by DUX4 or by mutations in SMCHD1 has not been reported yet. Here, we identified several types of small noncoding RNAs including known microRNAs that are differentially expressed in FSHD2 muscle cells compared to control. Although fewer small RNAs were differentially expressed during muscle differentiation in FSHD2 cells compared to controls, most of the known myogenic microRNAs, such as miR1, miR133a and miR206 were induced in both FSHD2 and control muscle cells during differentiation. Our small RNA sequencing data analysis also revealed both DUX4- and SMCHD1-specific changes in FSHD2 muscle cells. Six FSHD2 microRNAs were affected by DUX4 overexpression in control myoblasts, whereas increased expression of tRNAs and 5S rRNAs in FSHD2 muscle cells was largely recapitulated in SMCHD1-depleted control myoblasts. Altogether, our studies suggest that the small noncoding RNA transcriptome changes in FSHD2 might be different from those in FSHD1 and that these differences may provide new diagnostic and therapeutic tools specific to FSHD2.

Enhancement-mode transistors with uniform turn-on threshold voltage (Vth) can be achieved using low damage and low rate gate recess etching techniques. In this work, dry etching conditions for a AlGaN/GaN heterostructure with an ultra-low etching rate of 1.5 nm/min were demonstrated and we succeeded the possibility to achieve a low etch rate of an AlGaN/GaN heterostructure in a Cl2/BCl3 plasma using inductively coupled plasma (ICP). The etching development was successfully implemented in the achievement of a normally-off GaN/AlGaN based transistor. The optimal recess depth was determined after fabrication of various devices with different recess depth values and with various dry etching conditions and after examining the performances of fabricated devices various conditions, and determining the dependence of recess time. The optimized etching condition resulted in low damage and smooth morphology of the etched AlGaN/GaN surfaces. Fine control of the depth of the gate region recess was achieved for the AlGaN/GaN heterostructure without any etch-stop layer, and validated for the fabrication of field effect transistors (FETs) using conventional processes. The fabricated normally-off Al2O3/AlGaN/GaN MOSFETs delivered a high positive Vth of +5.64 V with a low off-state leakage current of ∼10−7 A/mm and lower current collapse.

The radiation hardness of AlGaN/GaN high-electron-mobility transistors (HEMTs) is found to improve with increasing GaN channel thickness. Epitaxial MgCaO shows promise as a radiation-tolerant gate dielectric, with only small shifts in operating parameters of metal–oxide–semiconductor HEMTs observed at doses up to 1 Mrad(SiO 2 ). Bias-induced electron trapping and radiation-induced-hole trapping can occur in the MgCaO, depending on the applied bias during stress and/or irradiation. AC transconductance measurements are used to help understand charge trapping in these devices.

In this paper, we investigated characteristics of AlGaN/GaN high-electron mobility transistors (HEMTs) with high resistive buffer structure consisted of periodically carbon-doped (PCD) GaN buffer layer and AlGaN back barrier layer. The PCD structure was proposed for reducing undesirable trapping effects, which resulted in effective suppression of the current collapse compared to that in conventional carbon buffer structure. To further improve the dynamic performances of the device and to increase the electron confinement of the 2-D electron gas (2-DEG) channel, AlGaN back barrier was inserted between the GaN channel and the PCD buffer layer, which results in greatly improved current collapse with slightly improved 2-DEG mobility compared to those of the device without back barrier. The OFF-state leakage current of the device with back-barrier is about 2 orders lower in magnitude than that of device without back barrier, which leads to the breakdown voltage of 2 kV and figure of merit of 2.27 GV2Ω-1cm-2 for the device with LGD of 10 μm, one of the highest values ever reported for the GaN-based HEMTs.

We report the electrical characteristics of GaN-based high electron mobility transistors (HEMTs) operated on various substrates/films. For the detailed investigation and comparison of the electrical properties of GaN-based HEMTs according to the substrates/films, GaN-based HEMTs were processed using 4-inch sapphire substrates and separated from their original substrates through the laser lift-off technique. The separated AlGaN/GaN films including processed GaN-based HEMTs were bonded to AlN substrate or plated with a 100 µm-thick Cu at the back-side of the devices since AlN substrate and Cu film exhibit higher thermal conductivity than the sapphire substrate. Compared to the sapphire substrate, DC and RF properties such as drain current, transconductance, cut-off frequency and maximum oscillation frequency were improved, when GaN-based HEMTs were operated on AlN substrate or Cu film. Our systematic study has revealed that the device property improvement results from the diminishment of the self-heating effect, increase in carrier mobility under the gated region, and amelioration of sheet resistance at the access region. C(V) and pulse-mode stress measurements have confirmed that the back-side processing for the device transfer from sapphire substrate onto AlN substrate or Cu film did not induce the critical defects close to the AlGaN/GaN hetero-interface.

We fabricated a 0.18-μm gate-length AlGaN/GaN high electron mobility transistor (HEMT) on SiC substrate fabricated by using two-step gate recessing which was composed of inductively coupled plasma (ICP) dry etching with a gas mixture of BCl3/Cl2 and wet chemical etching using the oxygen plasma treatment and HCl-based cleaning. The two-step gate recessing process exhibited an etch depth of 4.5 nm for the AlGaN layer and the clean surface of AlGaN layer at the AlGaN/gate metal contact region for the AlGaN/GaN HEMT structure. The recessed 0.18 μm × 200 μm AlGaN/GaN HEMT devices showed good DC characteristics, having a good Schottky diode ideality factor of 1.25, an extrinsic transconductance (g m ) of 345 mS/mm, and a threshold voltage (V th ) of −2.03 V. The recessed HEMT devices exhibited high RF performance, having a cut-off frequency (f T ) of 48 GHz and a maximum oscillation frequency (f max ) of 130 GHz. These devices also showed minimum noise figure of 0.83 dB and associated gain of 12.2 dB at 10 GHz.

In this paper, an enhanced-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) was developed by using 4-inch GaN HEMT process. We designed and fabricated Emode HEMTs and characterized device performance. To estimate the possibility of application for millimeter wave applications, we focused on the high frequency performance and power characteristics. To shift the threshold voltage of HEMTs we applied the Al2O3 insulator to the gate structure and adopted the gate recess technique. To increase the frequency performance the e-beam lithography technique was used to define the 0.15 um gate length. To evaluate the dc and high frequency performance, electrical characterization was performed. The threshold voltage was measured to be positive value by linear extrapolation from the transfer curve. The device leakage current is comparable to that of the depletion mode device. The current gain cut-off frequency and the maximum oscillation frequency of the E-mode device with a total gate width of 150 um were 55 GHz and 168 GHz, respectively. To confirm the power performance for mm-wave applications the load-pull test was performed. The measured power density of 2.32 W/mm was achieved at frequencies of 28 and 30 GHz.

Background Facioscapulohumeral muscular dystrophy (FSHD) is in most cases caused by a contraction of the D4Z4 macrosatellite repeat on chromosome 4 (FSHD1) or by mutations in the SMCHD1 or DNMT3B gene (FSHD2). Both situations result in the incomplete epigenetic repression of the D4Z4-encoded retrogene DUX4 in somatic cells, leading to the aberrant expression of DUX4 in the skeletal muscle. In mice, Smchd1 regulates chromatin repression at different loci, having a role in CpG methylation establishment and/or maintenance. Methods To investigate the global effects of harboring heterozygous SMCHD1 mutations on DNA methylation in humans, we combined 450k methylation analysis on mononuclear monocytes from female heterozygous SMCHD1 mutation carriers and unaffected controls with reduced representation bisulfite sequencing (RRBS) on FSHD2 and control myoblast cell lines. Candidate loci were then evaluated for SMCHD1 binding using ChIP-qPCR and expression was evaluated using RT-qPCR. Results We identified a limited number of clustered autosomal loci with CpG hypomethylation in SMCHD1 mutation carriers: the protocadherin (PCDH) cluster on chromosome 5, the transfer RNA (tRNA) and 5S rRNA clusters on chromosome 1, the HOXB and HOXD clusters on chromosomes 17 and 2, respectively, and the D4Z4 repeats on chromosomes 4 and 10. Furthermore, minor increases in RNA expression were seen in FSHD2 myoblasts for some of the PCDHβ cluster isoforms, tRNA isoforms, and a HOXB isoform in comparison to controls, in addition to the previously reported effects on DUX4 expression. SMCHD1 was bound at DNAseI hypersensitivity sites known to regulate the PCDHβ cluster and at the chromosome 1 tRNA cluster, with decreased binding in SMCHD1 mutation carriers at the PCDHβ cluster sites. Conclusions Our study is the first to investigate the global methylation effects in humans resulting from heterozygous mutations in SMCHD1. Our results suggest that SMCHD1 acts as a repressor on a limited set of autosomal gene clusters, as an observed reduction in methylation associates with a loss of SMCHD1 binding and increased expression for some of the loci. Electronic supplementary material The online version of this article (doi:10.1186/s13395-017-0129-7) contains supplementary material, which is available to authorized users.

AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated using a gate recess process and a surface treatment with tetramethylammonium hydroxide (TMAH) prior to gate metal deposition. Electrical characterizations show improved extrinsic transconductance and saturation current, as well as more uniform off-state behavior with reduced off-current by a factor of 3.5 and gate leakage current by a factor of 4.2 in the devices with TMAH treatment. The analyses based on atomic force microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy show that the TMAH treatment effectively reduces the roughness of the recess-etched AlGaN surface and removes the native oxide layer on the AlGaN surface, suggesting a simple and viable route towards the fabrication of gate-recessed HEMTs based on AlGaN/GaN heterostructure with improved controllability and uniformity.

We report the characteristics of InGaAs-based independent double-gate FinFETs with Al2O3/LaAlO3 as gate dielectric. The device can be operated in three different modes ( i.e., single-, double-, and independent double-gate) made possible by the physically separated two sidewall gates. When the device is operated in the double-gate mode, it exhibits better performance in terms of the On/Off current ratio, subthreshold swing, Off current, and channel mobility than in the single-gate mode. In addition, independent double-gate operation makes it possible to modulate channel properties by applying a bias at the opposite gate via gate coupling effects. Our systematic measurements reveal that gate control and coupling effects are enhanced with reduced fin width.

The high temperature storage (HTS) effects on the thermal stability and electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. The step-temperature storage tests in the temperature range from 150 °C to 325 °C were performed to evaluate the reliability of device. It was shown that the electrical properties of devices were remarkably changed as temperature increases. The values of the saturation current and the transconductance ranged from 187 mA to 299 mS/mm (fresh device) to 149 mA and 246 mS/mm (after HTS at 325 °C), respectively. In addition, the threshold voltage was shifted in a positive position and the leakage current was significantly decreased. In order to analyze the fundamental mechanisms of device degradation, we investigated the ohmic contact reliability by the transmission line model and analyzed the gate diode characteristics to estimate the diode parameters. It was found that Ti/Al/Ni/Au ohmic contact were stable and showed good thermal performance, but the Schottky contact was more sensitive to the HTS test. Failure analysis using electrical characterization of the gate diode and TEM/EDX cross-section revealed that the gate metal diffusion phenomenon was main degradation mechanism. During HTS test, Ni diffused out from the metal-semiconductor interface and Au formed a Schottky contact on AlGaN layer. To suppress the gate deformation, we adopted the optimum passivation and demonstrated its effect on the device reliability. By comparing the behavior of gate during HTS test, we clarified that the optimum passivation could suppress the diffusion related degradation mechanism and increase the reliability of AlGaN/GaN HEMTs.

In this study, we investigated the operational characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by applying the copper-filled trench and via structures for improved heat dissipation. Therefore, we used a basic T-gate HEMT device to construct the thermal structures. To identify the heat flow across the device structure, a thermal conductivity model and the heat transfer properties corresponding to the GaN, SiC, and Cu materials were applied. Initially, we simulated the direct current (DC) characteristics of a basic GaN on SiC HEMT to confirm the self-heating effect on AlGaN/GaN HEMT. Then, to verify the heat sink effect of the copper-filled thermal structures, we compared the DC characteristics such as the threshold voltage, transconductance, saturation current, and breakdown voltage. Finally, we estimated and compared the lattice temperature of a two-dimensional electron gas channel, the vertical lattice temperature near the drain-side gate head edge, and the transient thermal analysis for the copper-filled thermal trench and via structures. Through this study, we could optimize the operational characteristics of the device by applying an effective heat dissipation structure to the AlGaN/GaN HEMT.

This study investigates metal-insulator-semiconductor high electron mobility transistor DC characteristics with different gate dielectric layer compositions and thicknesses, and lattice temperature effects on gate leakage current by using a two-dimensional simulation. We first compared electrical properties, including threshold voltage, transconductance, and gate leakage current with the self-heating effect, by applying a single Si3N4 dielectric layer. We then employed different Al2O3 dielectric layer thicknesses on top of the Si3N4, and also investigated lattice temperature across a two-dimensional electron gas channel layer with various dielectric layer compositions to verify the thermal effect on gate leakage current. Gate leakage current was significantly reduced as the dielectric layer was added, and further decreased for a 15-nm thick Al2O3 on a 5-nm Si3N4 structure. Although the gate leakage current increased as Al2O3 thickness increased to 35 nm, the breakdown voltage was improved.

A short-circuited capacitor in a matching circuit between the third and fourth stages of an LNA has been used to reduce an unwanted small-signal gain at 50∼70 GHz and to flatten signal gain at an operating frequency of 77∼97 GHz. The designed LNA shows a small-signal gain of 21.2 to 22.2 dB, a gain flatness of 1 dB, a noise figure of 5.7 to 6.9 dB, an input-reflection coefficient of −14 to −7 dB, an output-reflection coefficient of −26 to −3 dB, an isolation of −51 to −44 dB, and an 1 dB bandwidth of 20 GHz over a frequency range of 76.6∼96.6 GHz. And the simulated power characteristic of the designed LNA present an 1 dB compression power, P IdB , of −3 to −1 dBm over a frequency range of 76.6∼96.6 GHz.

We propose a 5/12 ​V dual output DC-DC converter that can achieve high efficiency and a small size form factor. Using low temperature co-fired ceramic (LTCC)-based multi-layer circuits, the converter minimizes power losses caused by power and ground metal planes and reduces the size. The lateral dimension of the converter with nine LTCC layers was 35 ​mm ​× ​45 ​mm. The proposed converter was compatible with the outputs of typical electric bike batteries, which are 48 ​V and 36 ​V. At a full-load condition of 3.1 ​A ​at 5 ​V output and 2 ​A ​at 12 ​V output, the measured efficiency was 92.9% and 93.6% with a supply voltage of 48 ​V and 36 ​V, respectively. The measured line regulation with ±20% of an input voltage was lower than 0.75% and load regulation with a 10%–100% load change for the dual output was lower than 1.4%. Under the condition of 100% load for one output and 25%–100% load change for another output, the maximum cross-regulation was 1.7%. The dynamic load regulation and response was lower than 9.6% and 480 μs with 0%–100% load change, respectively, and the maximum ripple and noise was 33.2 mVpp. Reliability tests indicated that the average efficiency degradation rate was less than 0.002%/°C. The results of an electromagnetic interference (EMI) test indicated the converter satisfies the IEC61000-6-3 class B standard. The results show that the LTCC multilayer circuit substrate is suitable for a high-efficiency, high-density, high-output stability, and high-reliability in a power converter.

Microwave low-noise performance AlGaN/GaN HEMT on a SiC substrate with a wide head double-deck T-shaped gate has been reported. The HEMTs with gate-length ( $L_{\mathrm { {g}}})$ of $0.17~\mu \text{m}$ and source–drain spacing ( $L_{\mathrm { {sd}}})$ of $3.5~\mu \text{m}$ exhibited a maximum extrinsic transconductance of 360 mS/mm, a current gain cutoff frequency ( $f_{\mathrm { {T}}})$ of 50 GHz, a maximum oscillation frequency ( $f_{\mathrm { {max}}})$ of 149 GHz, and three-terminal breakdown voltage of 113 V. The device exhibited a minimum noise figure (NF $_{\mathrm { {min}}})$ of 0.50 and 0.84 dB at 10 and 18 GHz, respectively, when biased at $V_{\mathrm { {ds}}}= 5$ V and $I_{\mathrm { {ds}}}= 140$ mA/mm, which is the lowest noise characteristics ever reported for the GaN-based T-shaped gate HEMTs with gate length larger than $0.1~\mu \text{m}$ . This excellent noise performance is attributed to the reduction of the gate resistance resulting from a wide head T-shaped gate and the improved device characteristics.

Characterization of cellular dielectrophoretic (DEP) behaviors, when cells are exposed to an alternating current (AC) electric field of varying frequency, is fundamentally important to many applications using dielectrophoresis. However, to date, that characterization has been performed with monotonically increasing or decreasing frequency, not with successive increases and decreases, even though cells might behave differently with those frequency modulations due to the nonlinear cellular electrodynamic responses reported in previous works. In this report, we present a method to trace the behaviors of numerous cells simultaneously at the single-cell level in a simple, robust manner using dielectrophoretic tweezers-based force spectroscopy. Using this method, the behaviors of more than 150 cells were traced in a single environment at the same time, while a modulated DEP force acted upon them, resulting in characterization of nonlinear DEP cellular behaviors and generation of different cross-over frequencies in living cells by modulating the DEP force. This study demonstrated that living cells can have non-linear di-polarized responses depending on the modulation direction of the applied frequency as well as providing a simple and reliable platform from which to measure a cellular cross-over frequency and characterize its nonlinear property.

In this study, a high-performance AlGaN/GaN high electron mobility transistor (HEMT) is presented to improve its electrical operation by employing an inner field-plate (IFP) structure. Prior to the IFP structure analysis, we compared the measured and simulated direct current characteristics of the fabricated two-finger conventional T-shaped gate HEMTs. Then, the AlGaN/GaN HEMT with a drain-side field plate (FP) structure was suggested to enhance the breakdown voltage characteristics. The maximum breakdown voltage recorded with a 0.8 &mu, m stretched FP structure was 669 V. Finally, the IFP structure was interfaced with the gate head of the device to compensate the radio frequency characteristics, choosing the optimum length of the drain-side FP structure. Compared to the 0.8 &mu, m stretched FP structure, the IFP structure showed improved frequency characteristics with minimal difference to the breakdown voltage. The frequency variation caused by changing the passivation thickness was also analyzed, and the optimum thickness was identified. Thus, IFP AlGaN/GaN HEMT is a promising candidate for high-power and high-frequency applications.

The DUX4 transcription factor is encoded by a retrogene embedded in each unit of the D4Z4 macrosatellite repeat. DUX4 is normally expressed in the cleavage-stage embryo, whereas chromatin repression prevents DUX4 expression in most somatic tissues. Failure of this repression causes facioscapulohumeral muscular dystrophy (FSHD) due to mis-expression of DUX4 in skeletal muscle. In this study, we used CRISPR/Cas9 engineered chromatin immunoprecipitation (enChIP) locus-specific proteomics to characterize D4Z4-associated proteins. These and other approaches identified the Nucleosome Remodeling Deacetylase (NuRD) and Chromatin Assembly Factor 1 (CAF-1) complexes as necessary for DUX4 repression in human skeletal muscle cells and induced pluripotent stem (iPS) cells. Furthermore, DUX4-induced expression of MBD3L proteins partly relieved this repression in FSHD muscle cells. Together, these findings identify NuRD and CAF-1 as mediators of DUX4 chromatin repression and suggest a mechanism for the amplification of DUX4 expression in FSHD muscle cells., eLife digest The DNA sequences of humans and other mammals contain many repetitive regions. This repetition makes these regions difficult to study with conventional approaches, and so the exact role of repetitive DNA is not fully understood. A particular sequence of repetitive DNA that plays an important role in human health contains a gene called DUX4 in each repeat. DUX4 is normally active in stem cells and in early-stage embryos. This gene is then switched off or ‘silenced’ during later stages of development and in most cells of the body. However, in some individuals the DUX4 gene inappropriately activates in muscle cells. This causes a disease known as facioscapulohumeral muscular dystrophy (FSHD), in which muscle weakness begins in the face and upper body and eventually spreads to other muscles. Currently, there is no cure for FSHD. Proteins that bind to DNA can control the activity of nearby genes. Little is known about which proteins silence DUX4 at the appropriate time and in the right cells, so Campbell et al. set out to identify the proteins that attach to the repetitive DNA sequences containing DUX4. Further investigation showed that several of these proteins play an important role in keeping DUX4 turned off, including two protein complexes called NuRD and CAF-1. These complexes are necessary to silence DUX4 in human muscle cells and stem cells. Campbell et al. also identified a protein that can increase the activity of the DUX4 gene in FSHD muscle cells by overcoming the silencing activity of the NuRD complex. Overall, the results presented by Campbell et al. provide the groundwork for developing new treatments for FSHD. The next step will be to discover ways of enhancing the ability of NuRD and CAF-1 to silence the DUX4 gene.

International audience; Normally-off AlGaN/GaN-based MOS-HEMT has been fabricated by utilizing damage-free self-terminating tetramethyl ammonium hydroxide (TMAH) recess etching. The device exhibited a threshold voltage of +2.0 V with good uniformity, extremely small hysteresis of ∼20 mV, and maximum drain current of 210 mA/mm. The device also exhibited excellent off-state performances, such as breakdown voltage of ∼800 V with off-state leakage current as low as ∼10−12 A and high on/off current ratio (Ion/Ioff) of 1010. These excellent device performances are believed to be due to the high quality recessed surface, provided by the simple self-terminating TMAH etching. Previous article in issue

We fabricated a 0.17-μm gate-length AlGaN/GaN high electron mobility transistor (HEMT) on SiC recessed by using ICP gate etching with a gas mixture of BCl3/Cl2. The ICP gate recess process exhibited an etch rate of 20 nm/min for the AlGaN layer and the clean surface characteristics at the etched AlGaN/gate metal interface for the AlGaN/GaN HEMT devices. The recessed 0.17 μm × 200 μm AlGaN/GaN HEMT devices showed good DC characteristics, having a high gateto-drain breakdown voltage of -177 V, a good Schottky diode ideality factor of 1.32, an extrinsic transconductance (g m ) of 245 mS/mm, and a threshold voltage (V th ) of -2.6 V. The recessed 0.17 μm × 200 μm AlGaN/GaN HEMT devices also exhibited high RF performance, having a cut-off frequency (f T ) of 46 GHz and a maximum oscillation frequency (f max ) of 150 GHz.

SiC substrates and GaN/AlGaN epitaxial layers were etched by using an inductively-coupled plasma (ICP) in order to electrically connect the backside metal to the source electrode pads on the front-side of an AlGaN/GaN high-electron-mobility transistor (HEMT) device. The shape of an etched via hole was a tapered cylinder with a larger diameter at the entrance. The surfaces on the bottom and a wall of the via hole were very smooth in comparison with the results on the most recently published papers. Through optimization of the etching conditions, the etch-stops on the GaN epi-layer and on the source pad were successfully completed. The electrical properties of the device with the backside via holes were not critically different from those of the device without the backside via holes. In this paper, the fabrication process and the electrical properties of AlGaN/GaN HEMTs on SiC substrates with taper-shaped backside via holes are reported for the first time.

Low ohmic contact resistance and smooth AlGaN/GaN surface morphology were obtained on a 2-inch c-plane sapphire substrate by using stepwise annealing at three different temperatures. Metallization was performed under deposition of a composite metal layer of Ti/Al/Ni/Au with thickness variations of 30 nm/100 nm/30 nm/100 nm (MS1), 15 nm/220 nm/40 nm/50 nm (MS2), 20 nm/120 nm/55 nm/45 nm (MS3), 15 nm/120 nm/40 nm/50 nm (MS5) and 20 nm/200 nm/55 nm/45 nm (MS6) and of Au/Ge/Au/Ge/Pt with thicknesses of 120 nm/60 nm/120 nm/60 nm/85 nm (MS4), respectively. After multi-layer metal stacking, a rapid thermal annealing (RTA) process was applied with a stepwise annealing temperature profile of 400°C for 180 s, 900°C for 30 s and 940°C for 30 s. We obtained a minimum specific contact resistance of ρc = 4.3 × 10−7 cm2 for MS1, ρc = 1.0 × 10−4 cm2 for MS2, ρc = 3.2 × 10−6 cm2 for MS3, ρc = 5.4 × 10−8 cm2 for MS5 and ρc = 1.1 × 10−7 cm2 for MS6.

© 2017 The Royal Society of Chemistry. Magnetic nanoparticles (MNPs) are widely used in biomedical and clinical applications, including medical imaging, therapeutics, and biological sample processing. Rapid characterization of MNPs, notably their magnetic moments, should facilitate optimization of particle synthesis and accelerate assay development. Here, we report a compact and low-cost magnetometer for fast, on-site MNP characterization. Termed integrated microHall magnetometer (iHM), our device was fabricated using standard semiconductor processes: an array of Hall sensors, transistor switches, and amplifiers were integrated into a single chip, thus improving the detection sensitivity and facilitating chip operation. By applying the iHM, we demonstrate versatile magnetic assays. We measured the magnetic susceptibility and moments of MNPs using small sample amounts (∼10 pL), identified different MNP compositions in mixtures, and detected MNP-labeled single cells.

This article describes the successful development and the performance of X-band 100 W pulsed SSPA using a 25 W GaN-on-SiC high electron mobility transistor (HEMT). The GaN HEMT with a gate length of 0.25 µm and a total gate width of 8 mm were fabricated. The GaN HEMT provide a linear gain of 8 dB with 25 W output power operated at 30 V drain voltage in continuous wave (CW)-operation with a power added efficiency of 43% at X-band. It also shows a maximum output power density of 3 W/mm. The X-band pulsed SSPA exhibited an output power of 100 W (50 dBm) with a power gain of 53 dB in a frequency range of 9.2–9.5 GHz. This 25 W GaN HEMT and X-band 100 W pulsed SSPA are suitable for the radar systems and related applications in X-band. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:212–216, 2015

This paper demonstrates normally-off dual gate AlGaN/GaN MISFETs with a selective area-recessed floating gate fabricated on the AlGaN/GaN-based heterostructure with an AlN insertion layer. For the fabrication of the dual gate structure, the AlGaN layer in the control gate region was fully recessed and then an Al2O3 layer as a gate dielectric was deposited by the atomic layer deposition method, which ensures the normally-off operation and greatly decreases the leakage current. An additional floating gate with selective area-recessed patterns, which is located between the control gate and the drain electrode, was employed to enhance the breakdown voltage. The fabricated normally-off dual gate AlGaN/GaN MISFET exhibited a threshold voltage of 2 V, a high ION/IOFF ratio of 3 × 108 at a drain voltage of 10 V, a maximum transconductance of 88 mS/mm at a gate voltage of 5.8 V, a drain current density of 364 mA/mm at a gate voltage of 8 V, and a breakdown voltage of 880 V.

We report the fabrication and DC and microwave characteristics of 0.5 μm AlGaN/GaN high electron mobility transistors using double plasma treatment process. Silicon nitride layers 700 and 150 A thick were deposited by plasma-enhanced chemical vapor deposition at 260 °C to protect the device and to define the gate footprint. The double plasma process was carried out by two different etching techniques to obtain enhancement-mode AlGaN/GaN high electron mobility transistors with 0.5 μm gate lengths. The enhancement-mode AlGaN/GaN high electron mobility transistor was prepared in parallel to the depletion-mode AlGaN/GaN high electron mobility transistor device on one wafer. Completed double plasma treated 0.5 μm AlGaN/GaN high electron mobility transistor devices fabricated by dry etching exhibited a peak transconductance, gm, of 330 mS/mm, a breakdown voltage of 115 V, a current-gain cutoff frequency ( f T ) of 18 GHz, and a maximum oscillation frequency ( f max ) of 66 GHz.

In counterfire warfare, it is important to detect and attack enemy targets faster than the enemy using sensing and shooting assets. The artillery assets of North Korea are mostly mine artillery and much more than those of South Korea. To cope with sudden fire attacks from North Korea, we need to improve capability of our artillery. In this paper, we discuss issues and problems of our counterfire warfare systems and processes to overcome numerical inferiority and defend against the mine artillery. We develop a simulation model for counterfire warfare and analyze effectiveness of our counterfire weapon systems and operations based on various counterfire warfare scenarios. Finally, we propose methods of tactical operations and acquisition strategies of counterfire weapon systems, including detaction, firing, and protection assets.Keywords : Counterfire Warfare(대화력전), Tactical Operations(전술적 운용), Acquisition(획득), Mine Artillery(갱도포병)

A dielectric resonator antenna with broad bandwidth at millimeter wave band is presented. This antenna is fabricated using low temperature cofired ceramics (LTCC) process, which is one of the most promising candidates for system-in-package (SiP) technology. The proposed antenna is an aperture coupled dielectric resonator antenna. The central region surrounded by equally spaced metallic vias act as a dielectric resonator, and an aperture for the signal feeding is located on the bottom of the resonator. The simulated antenna bandwidth is as wide as 11.7 GHz (55.4–67.1 GHz), and the measured bandwidth decreases to 9.6 GHz (56.5–66.1 GHz), which is still wider than the internationally allocated bandwidth for the communication.

Surface passivation of AlGaN/GaN heterojunction structure was examined through the thermal oxidation of evaporated Al. The Al-oxide passivation increased channel conductance of two dimensional electron gas (2DEG) on the AlGaN/GaN interface. The sheet resistance of 463 ohm/ for 2DEG channel before passivation was decreased to 417 ohm/ after passivation. The oxidation of Al induces tensile stress to the AlGaN/GaN structure and the stress seemed to enhance the sheet carrier density of the 2DEG channel. In addition, the films formed by thermal oxidation of Al suppressed thermal deterioration by the high temperature annealing.

To better understand transcriptional regulation during human oogenesis and preimplantation development, we defined stage-specific transcription, which highlighted the cleavage stage as being highly distinctive. Here, we present multiple lines of evidence that a eutherian-specific multicopy retrogene, DUX4, encodes a transcription factor that activates hundreds of endogenous genes (for example, ZSCAN4, KDM4E and PRAMEF-family genes) and retroviral elements (MERVL/HERVL family) that define the cleavage-specific transcriptional programs in humans and mice. Remarkably, mouse Dux expression is both necessary and sufficient to convert mouse embryonic stem cells (mESCs) into 2-cell-embryo-like ('2C-like') cells, measured here by the reactivation of '2C' genes and repeat elements, the loss of POU5F1 (also known as OCT4) protein and chromocenters, and the conversion of the chromatin landscape (as assessed by transposase-accessible chromatin using sequencing (ATAC-seq)) to a state strongly resembling that of mouse 2C embryos. Thus, we propose mouse DUX and human DUX4 as major drivers of the cleavage or 2C state.

Krüppel-like zinc finger transcription factors compose the largest transcription factor family in the mammalian genome. However, the functions for the majority of these transcription factors as well as their in vivo downstream targets are not clear. We have functionally characterized a novel KRAB domain zinc finger transcription factor ZNF431 using both in vitro and in vivo assays. ZNF431 is a nuclear transcriptional repressor whose repressive activity depends on its association with HDAC1 and -2. Using the limb mesenchymal cell line MPLB, we identified Patched1 as a direct transcriptional target of ZNF431. Promoter analyses revealed three ZNF431 binding sites that bind to ZNF431 both in vitro and in vivo as revealed by gel-shift and chromatin immunoprecipitation, respectively. Mutations of these three sites abolished ZNF431 repression in transient transfection assays. Moreover, overexpressing ZNF431 in MPLB cells or in Xenopus and mouse embryos strongly repressed Patched1 expression. On the other hand, shRNA knockdown of ZNF431 in MPLB cells elevated Patched1 expression. Finally, hedgehog signaling readout was reduced in ZNF431 overexpression but elevated in ZNF431 knockdown MPLB cells. Our results indicate that ZNF431 directly represses Patched1 expression and likely functions to repress the hedgehog response in cells.

In this article, 60 GHz MMIC down-conversion mixers for a 60 GHz communication system are designed and fabricated on-chip using a 0.12 μm GaAs PHEMT process technology with an fT of 78 GHz and fmax of 190 GHz.The characteristics of a 60 GHz monolithic cascode mixer with an open stub microstrip line are compared with those of a 60 GHz monolithic cascode mixer without an open stub microstrip line, which are integrated on-chip including matching and bias circuits. The 60 GHz monolithic cascode mixer with an open stub microstrip line measured at RF 60 GHz show a conversion gain of −16 dB, LO to RF isolation of 21.5 dB, and LO to IF isolation of 40.5 dB. Especially in the case of the mixer, the LO to IF isolation characteristic is much better than that of the 60 GHz monolithic cascode mixer without an open stub microstrip line. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1341–1345, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25191

We present an analysis of microstrip coupled lines (MCLs) used to improve the stability of a 60 GHz narrowband amplifier. The circuit has a 4-stage structure implementing MCLs instead of metal-insulator-metal (MIM) capacitors for the unconditional stability of the amplifier and yield enhancement. The stability parameter, U, is used to compare the stability of MCLs with that of MIM capacitors. Experimental results show that MCLs are more stable than MIM capacitors with the same capacitances as MCLs because the parasitic parallel resistances of MCLs are lower than those of MIM capacitors. Moreover, the bandwidth of an amplifier using MCLs is narrower than one using MIM capacitors because the parasitic series inductances of MCLs are higher than those of MIM capacitors.

This study examines the effect of multiknowledge individuals (especially those possessing both marketing and technological knowledge) on performance in cross-functional new product development teams. A survey of 62 cross-functional teams shows that the proportion of multiknowledge individuals has an indirect positive effect through information sharing on product innovativeness and a direct positive effect on time efficiency of new product development teams.

Proneural basic helix–loop–helix proteins are key regulators of neurogenesis but their ‘proneural’ function is not well understood, partly because primary targets have not been systematically defined. Here, we identified direct transcriptional targets of the bHLH proteins Neurogenin and NeuroD and found that primary roles of these transcription factors are to induce regulators of transcription, signal transduction, and cytoskeletal rearrangement for neuronal differentiation and migration. We determined targets induced in both Xenopus and mouse, which represent evolutionarily conserved core mediators of Neurogenin and NeuroD activities. We defined consensus sequences for Neurogenin and NeuroD binding and identified responsive enhancers in seven shared target genes. These enhancers commonly contained clustered, conserved consensus‐binding sites and drove neural‐restricted transgene expression in Xenopus embryos. We then used this enhancer signature in a genome‐wide computational approach to predict additional Neurogenin/NeuroD target genes involved in neurogenesis. Taken together, these data demonstrate that Neurogenin and NeuroD preferentially recognize neurogenesis‐related targets through an enhancer signature of clustered consensus‐binding sites and regulate neurogenesis by activating a core set of transcription factors, which build a robust network controlling neurogenesis.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by the aberrant expression of the DUX4 transcription factor in skeletal muscle. The DUX4 retrogene is encoded in the D4Z4 macrosatellite repeat array, and smaller array size or a mutation in the SMCHD1 gene results in inefficient epigenetic repression of DUX4 in skeletal muscle, causing FSHD1 and FSHD2, respectively. Previously we showed that the entire D4Z4 repeat is bi-directionally transcribed with the generation of small si- or miRNA-like fragments and suggested that these might suppress DUX4 expression through the endogenous RNAi pathway. Here we show that exogenous siRNA targeting the region upstream of the DUX4 transcription start site suppressed DUX4 mRNA expression and increased both H3K9 methylation and AGO2 recruitment. In contrast, similarly targeted MOE-gapmer antisense oligonucleotides that degrade RNA but do not engage the RNAi pathway did not repress DUX4 expression. In addition, knockdown of DICER or AGO2 using either siRNA or MOE-gapmer chemistries resulted in the induction of DUX4 expression in control muscle cells that normally do not express DUX4, indicating that the endogenous RNAi pathway is necessary to maintain repression of DUX4 in control muscle cells. Together these data demonstrate a role of the endogenous RNAi pathway in repeat-mediated epigenetic repression of the D4Z4 macrosatellite repeat, and show that enhancing the activity of this pathway by supplying exogenous siRNA oligonucleotides represents a potential therapeutic approach to silencing DUX4 in FSHD.

We report the fabrication and DC and microwave characteristics of 0.12 µm double-recessed T-gate AlGaAs/InGaAs/GaAs pseudomorphic high-electron-mobility transistors (PHEMTs) using dielectric-assisted process. Silicon nitride layers 300 and 200 A thick were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 260 °C to protect the device and to define the gate footprint. The double-recess process was carried out by two different etching techniques to obtain double-recessed T-gates with 0.12 µm gate lengths. Completed double-recessed T-gate AlGaAs/InGaAs/GaAs pHEMT devices fabricated using dry etching exhibited a peak transconductance, gm, of 765 mS/mm, a current-gain cutoff frequency ( fT) as high as 124 GHz, and a maximum oscillation frequency ( fmax) of 247 GHz. The fabricated low-noise amplifier (LNA) has a measured gain of more than 20 dB in the 62.75 to 64.75 GHz frequency range.

We report on the fabrication of an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) using a dielectric-defined process. This process was utilized to fabricate 0.12 µm × 100 µm T-gate PHEMTs. A two-step etch process was performed to define the gate footprint in the SiNx. The SiNx was etched either by dry etching alone or using a combination of wet and dry etching. The gate recessing was done in three steps: a wet etching for removal of the damaged surface layer, a dry etching for the narrow recess, and wet etching. A structure for the top of the T-gate consisting of a wide head part and a narrow lower layer part has been employed, taking advantage of the large crosssectional area of the gate and its mechanically stable structure. From s-parameter data of up to 50 GHz, an extrapolated cut-off frequency of as high as 104 GHz was obtained. When comparing sample C (combination of wet and dry etching for the SiN x ) with sample A (dry etching for the SiNx), we observed an 62.5% increase of the cut-off frequency. This is believed to be due to considerable decreases of the gate-source and gate-drain capacitances. This improvement in RF performance can be understood in terms of the decrease in parasitic capacitances, which is due to the use of the dielectric and the gate recess etching method.