InAs Channel Research Articles

The Potential Mechanisms behind Loperamide-Induced Cardiac Arrhythmias Associated with Human Abuse and Extreme Overdose.

Loperamide has been a safe and effective treatment for diarrhea for many years. However, many cases of cardiotoxicity with intentional abuse of loperamide ingestion have recently been reported. We evaluated loperamide in in vitro and in vivo cardiac safety models to understand the mechanisms for this cardiotoxicity. Loperamide slowed conduction (QRS-duration) starting at 0.3 µM [~1200-fold (×) its human Free Therapeutic Plasma Concentration; FTPC] and reduced the QT-interval and caused cardiac arrhythmias starting at 3 µM (~12,000× FTPC) in an isolated rabbit ventricular-wedge model. Loperamide also slowed conduction and elicited Type II/III A-V block in anesthetized guinea pigs at overdose exposures of 879× and 3802× FTPC. In ion-channel studies, loperamide inhibited hERG (IKr), INa, and ICa currents with IC50 values of 0.390 µM, 0.526 µM, and 4.091 µM, respectively (i.e., >1560× FTPC). Additionally, in silico trials in human ventricular action potential models based on these IC50s confirmed that loperamide has large safety margins at therapeutic exposures (≤600× FTPC) and confirmed repolarization abnormalities in the case of extreme doses of loperamide. The studies confirmed the large safety margin for the therapeutic use of loperamide but revealed that at the extreme exposure levels observed in human overdose, loperamide can cause a combination of conduction slowing and alterations in repolarization time, resulting in cardiac proarrhythmia. Loperamide's inhibition of the INa channel and hERG-mediated IKr are the most likely basis for this cardiac electrophysiological toxicity at overdose exposures. The cardiac toxic effects of loperamide at the overdoses could be aggravated by co-medication with other drug(s) causing ion channel inhibition.

Improvement of single event effects in InP-based HEMT with a composite channel of InGaAs/InAs/InGaAs

In this paper, a hardened single event effects in InP-based HEMT with a InGaAs/InAs/InGaAs composite channel (CC HEMT) is investigated by the two-dimensional numerical simulations. The composite channel significantly improves the single event effects. Compared to the conventional InP-based HEMT with single InGaAs channel (SC HEMT), the peak drain current is markedly decreased for CC HEMT, owing to a high barrier in the InGaAs/InAs/InGaAs locates electrons in the middle of the sandwiched layer. In addition, the electron concentration of the InAs channel is smaller of CC HEMT than that of InGaAs channel of SC HEMT after ion strike. This also makes the decrease in drain current. Through optimal device parameters, the peak drain current of the CC HEMT with 9/1/5 nm In0.8Ga0.2As/InAs/In0.8Ga0.2 channel is 129.1 % smaller than that of the SC HEMT with In0.53Ga0.47 channel.

Ticagrelor Can Regulate the Ion Channel Characteristics of Superior Cervical Ganglion Neurons after Myocardial Infarction.

The superior cervical ganglion (SCG) plays a key role in cardiovascular diseases. The aim of this study was to determine the changes in the ion channel characteristics of the SCG following myocardial infarction (MI) and the role of pretreatment with the P2Y12 receptor antagonist ticagrelor (TIC). A total of 18 male rabbits were randomly divided into a control group, MI group, and P2Y12 receptor antagonist (TIC) group (abbreviated as the TIC group). Rabbit MI was performed via two abdominal subcutaneous injections of 150 mg·kg-1·d-1 of isoproterenol (ISO) with an interval of 24 h. TIC pretreatment at 20 mg·kg-1·d-1 was administered via gavage for two consecutive days. The cardiac function of each group was evaluated with echocardiography. ADP receptor P2Y12 expressions in SCGs were determined using RT-PCR and immunofluorescence staining. Ion channel characteristics of SCG neurons were measured using a whole-cell patch clamp. Intracellular calcium concentrations for SCG neurons were measured using confocal microscopy. Cardiac function was reduced in the rabbits of the MI group, the sympathetic nerve activity of SCGs was increased, and the current amplitude of the neuron ion channel was increased. MI led to alterations in the activation and inactivation characteristics of INa channels accompanied by increased expression of P2Y12 in SCGs. Most of these abnormalities were prevented by TIC pretreatment in the TIC group. TIC pretreatment could attenuate the increase in P2Y12 expression in SCGs and the changes to the ion channel characteristics of SCG neurons after MI. This may be the mechanism underlying the cardiac protective effects of TIC.

Design and Investigation of a Metamorphic InAs Channel Inset InP HEMT for Cryogenic Low-Noise Amplifiers

Design and Investigation of a Metamorphic InAs Channel Inset InP HEMT for Cryogenic Low-Noise Amplifiers

Estudo sobre os mecanismos dos polissacarídeos de Suaeda rigida na inibição do coração e promoção da musculatura esquelética no sapo

ABSTRACT The objectives of this study were to investigate the effects of different concentrations of Suaeda rigida polysaccharides (SRPs) on the physiological characteristics of the frog heart and gastrocnemius muscle, compare their similarities and differences, and analyze the mechanisms. CaCl2 and acetylcholine (Ach) were selected respectively to be co-incubated with the high concentration SRPs to observe the effects on the heart contraction of frog. The effects of different concentrations of the SRPs on the activities of acetylcholinesterase (A-CHE), Na+-K+-ATPase and Ca2+-Mg2+-ATPase in the isolated frog heart were detected by UV-Vis spectrophotometry. The gastrocnemius muscle was immersed in the high concentration of SRPs for 10 min, and the systolic indexes were recorded. The effects of SRPs on the Ach content and A-CHE activity at the sciatic nerve-gastrocnemius junction were determined by UV-Vis spectrophotometry and enzyme-linked immunosorbent assay (ELISA). The results showed that the SRPs had significant inhibitory effects on the contractile amplitude of isolated heart and the contractile amplitude induced by CaCl2 and Ach, respectively (P<0.01). The activity of Ca2+-Mg2+-ATPase was significantly promoted, and the activity of A-CHE was significantly inhibited (P<0.01). The contraction amplitude, contraction rate, relaxation rate of gastrocnemius muscle and the Ach content at the junction of sciatic nerve-gastrocnemius muscle were significantly increased (P<0.01), and the activity of A-CHE at the junction was significantly inhibited (P<0.01) by the SRPs. All the results suggested that the SRPs could inhibit the contraction of heart and promote the contraction and relaxation of skeletal muscle. The mechanism was related to blocking the fast INa channel, inhibiting the ICa-L and activating the M receptors of myocardial membrane and then inhibiting external Ca2+ influx, increasing Ca2+-Mg2+-ATPase activity, decreasing a-che activity.

Electrical Properties of Selective-Area-Grown Superconductor-Semiconductor Hybrid Structures on Silicon

We present a superconductor-semiconductor material system that is both scalable and monolithically integrated on a silicon substrate. It uses selective area growth of Al-InAs hybrid structures on a planar III-V buffer layer, grown directly on a high resistivity silicon substrate. We characterized the electrical properties of this material system at millikelvin temperatures and observed a high average field-effect mobility of $\mu \approx 3200\,\mathrm{cm^2/Vs}$ for the InAs channel, and a hard induced superconducting gap. Josephson junctions exhibited a high interface transmission, $\mathcal{T} \approx 0.75 $, gate voltage tunable switching current with a product of critical current and normal state resistance, $I_{\mathrm{C}}R_{\mathrm{N}} \approx 83\,\mathrm{\mu V}$, and signatures of multiple Andreev reflections. These results pave the way for scalable and high coherent gate voltage tunable transmon devices and other superconductor-semiconductor hybrids fabricated directly on silicon.

Cardiac toxicity from bisphenol A exposure in human-induced pluripotent stem cell-derived cardiomyocytes

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical that is widely used in a variety of products, including plastics, medical equipment and receipts. Hence, most people are exposed to BPA through the skin, via inhalation and via the digestive system, and such exposure has been linked to cardiovascular diseases including coronary artery disease, hypertension, atherosclerosis, and myocardial infarction. However, the underlying mechanisms of cardiac dysfunction caused by BPA remain poorly understood. In this study, we found that BPA exposure altered cardiac function in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Acute BPA exposure in hiPSC-CMs resulted in reduced field potential, as measured by multielectrode array (MEA). Furthermore, we observed that BPA dose-dependently inhibited ICa, INa or IKr channels. In addition, BPA exposure dose-dependently inhibited calcium transients and contraction in hiPSC-CMs. Our findings suggest that BPA exposure leads to cardiac dysfunction and cardiac risk factors such as arrhythmia.

Proposal and Experimental Demonstration of Ultrathin-Body (111) InAs-On-Insulator nMOSFETs With L Valley Conduction

Ultrathin-body (UTB) (111) InAs-On-Insulator (InAs-OI) n-channel metal–oxide–semiconductor field-effect transistors (nMOSFETs) are proposed as a new technology booster using the L valley conduction in III–V channels. The performance of the conventional UTB III–V nMOSFETs is limited by the essential band features of the $\Gamma $ valley conduction such as the low density of states, resulting in low inversion capacitance, and the light effective mass ${m}_{z}$ along the confinement direction, resulting in strong thickness fluctuation scattering. The strong confinement of electrons by a combination of (111) surface orientation and UTB InAs-OI structures is expected to transfer the electrons into the L valley with much heavier ${m}_{z}$ than in the $\Gamma $ valley, leading to higher semiconductor capacitance and suppression of thickness fluctuation scattering. We also experimentally demonstrate the UTB (111) InAs-OI nMOSFETs operation with thinning the InAs channels down to 3 nm, realized by the smart-cut and digital etching process. Channel thickness scaling improves both the OFF- and ON-currents by expansion of the effective bandgap. It is shown that the measured mobility increases with decreasing InAs-OI thickness from 4.8 to 4.4 nm, which is attributable to the increase in the electron occupancy in the L valley.

Nonuniform Carrier Heating Induced Nonlinear Electron Transport Properties in Asymmetrically Necked InAs Mesa Structures

IntroductionTerahertz (THz) wave has been very attractive light for scientific and practical applications such as light source for characterizing fundamental physics on ultra-fast carrier dynamics in semiconductors and imaging applications in the submillimeter wavelength regime. Therefore, there have been studied on various kind of emitting and detecting methods on THz waves in this quarter century. So far, we also have proposed simple and low-cost THz wave source with InAs thin films grown on GaAs substrates combining with a time-domain spectroscopy system [1, 2]. In case of THz detectors, there are not so many techniques which enable to detect THz wave at room temperature with high responsivity without biasing. For example, square-law field rectifier detectors, such as Schottky diodes and InGaAs-based bow-tie diodes, respond to THz electric field at room temperature with no external power supply [3]. Nonlinear current-voltage characteristics of the latter technique is based on unique operation principle which is generated by nonuniform carrier heating in asymmetric bow-tie shaped planar structures. Since InAs possesses one of the highest electron mobility at room temperature among semiconductors, this material based thin films will be hopeful candidate for detecting THz waves by fabricating this unique nonlinear device structures on them. In this paper, we devise utilizing InAs THz wave emitter thin films to base material for asymmetrically necked bow-tie mesa structures for the THz detector. As a first step of this idea, nonlinear current-voltage characteristics of these devices are presented. We especially discuss on the curvature of current-voltage characteristic at zero-bias point which is closely related to the sensitivity on square-law detection for THz wave.ExperimentalNominally undoped InAs thin films were epitaxially grown on semi-insulating GaAs (100) substrate by molecular beam epitaxy. For improving the crystal quality of InAs channel layer, 150 nm thick InAs buffer layer was directly grown with gradually changing growth temperature from 300 to 500°C on GaAs substrate. An 1 µm think InAs channel layer was grown on this buffer layer at 450°C. This growth condition is same as that of THz emitter InAs films we have reported [2]. The patterning of asymmetric bow-tie mesa structure was carried out by photo lithography and phosphoric acid based wet chemical etching. After defining mesa structures, in order to investigate the film thickness dependence on nonlinear current properties, some samples were performed recess etching for InAs channel, which were made each thickness to be 265 nm, 435 nm, 625 nm and 835 nm. Finally, non-alloyed ohmic contact metals of Ti/Pt/Au (50/30/170 nm) were deposited by electron-beam evaporation technique and defined by lift-off. The structure of asymmetric bow-tie diode and the measurement configuration are shown in Fig. 1. Current-voltage characteristics were measured by using Keithley 4200A-SCS system at room temperature.Results and Conclusion Typical current-voltage characteristic of the investigated InAs asymmetric bow-tie diode is represented in Fig. 2, which was the result measured with the sample of 265 nm thick InAs channel. It showed clear asymmetric current-voltage characteristic depended on the polarity of applied voltage, which was considered originated from nonlinear carrier transport related to non-uniform carrier heating in asymmetric mesa structure. In order to evaluate the nonlinearity of current-voltage curve at zero-biased point, the zero-biased curvature coefficient γ was calculated, which is given by the formula written in Fig. 3. A fifth order polynomial fit was utilized to current-voltage curves in determining the curvature. As shown in Fig. 3, the zero-bias curvature clearly depended on thickness of InAs thin film. The highest zero-bias curvature of 0.12 V-1 was obtained in the thinnest sample. In addition, this value was about 2.2 times larger than that of the GaAs/AlGaAs heterostructure-based asymmetric bow-tie diode which had the same shape and size (not shown here). These results indicate that the InAs thin film for THz radiation has possibility to be applied to square-law detection device for THz wave. The details of nonlinearity which depends on mesa shape and size and comparison between InAs based structures and that of GaAs/AlGaAs will be discussed at the conference.

Silica Nanoparticles Disturb Ion Channels and Transmembrane Potentials of Cardiomyocytes and Induce Lethal Arrhythmias in Mice.

BackgroundThe toxicity of silica nanoparticles (SiNPs) on cardiac electrophysiology has seldom been evaluated.MethodsPatch-clamp was used to investigate the acute effects of SiNP-100 (100 nm) and SiNP-20 (20 nm) on the transmembrane potentials (TMPs) and ion channels in cultured neonatal mouse ventricular myocytes. Calcium mobilization in vitro, cardiomyocyte ROS generation, and LDH leakage after exposure to SiNPs in vitro and in vivo were measured using a microplate reader. Surface electrocardiograms were recorded in adult mice to evaluate the arrhythmogenic effects of SiNPs in vivo. SiNP endocytosis was observed using transmission electron microscopy.ResultsWithin 30 min, both SiNPs (10−8–10−6 g/mL) did not affect the resting potential and IK1 channels. SiNP-100 increased the action potential amplitude (APA) and the INa current density, but SiNP-20 decreased APA and INa density. SiNP-100 prolonged the action potential duration (APD) and decreased the Ito current density, while SiNP-20 prolonged or shortened the APD, depending on exposure concentrations and increased Ito density. Both SiNPs (10−6 g/mL) induced calcium mobilization but did not increase ROS and LDH levels and were not endocytosed within 10 min in cardiomyocytes in vitro. In vivo, SiNP-100 (4–10 mg/kg) and SiNP-20 (4–30 mg/kg) did not elevate myocardial ROS but increased LDH levels depending on dose and exposure time. The same higher dose of SiNPs (intravenously injected) induced tachyarrhythmias and lethal bradyarrhythmias within 90 min in adult mice.ConclusionSiNPs (i) exert rapid toxic effects on the TMPs of cardiomyocytes in vitro largely owing to their direct interfering effects on the INa and Ito channels and Ca2+ homeostasis but not IK1 channels and ROS levels, and (ii) induce tachyarrhythmias and lethal bradyarrhythmias in vivo. SiNP-100 is more toxic than SiNP-20 on cardiac electrophysiology, and the toxicity mechanism is likely more complicated in vivo.

Requirements of epitaxially grown InGaAs channel layers for tunnel field-effect transistors

The requirements of the epitaxially grown InGaAs channel layers for tunnel field-effect transistors (TFETs) have been studied by a comparison between the experimental results and technology computer-aided design (TCAD) simulations. It is observed that the threshold voltage (Vth) of InGaAs TFETs with high In contents is shifted more toward the negative bias direction and the off-characteristics are degraded more than that expected in simulation results. These results are attributable to the increase in n-type effective carrier concentration (Nch) in the InGaAs and InAs channels, which can be caused by lattice relaxation because of the large lattice mismatch between the epitaxial layer and the substrate. The use of a thin channel layer with high In content InGaAs and/or InAs can be a solution for achieving high on-current and low off-current simultaneously. It is found that p-type doping in the InGaAs and InAs channels can mitigate the degradation of the cut-off properties. Moreover, it is observed that increased Nch by unintentional Si impurity atoms at the epitaxial layer and the substrate interface can affect the performance of TFETs with thin InGaAs channels, which can be suppressed by introducing an insertional undoped buffer layer. The impact of Nch is also studied for the short channel devices by TCAD simulations. The p-type doping in InGaAs channels can also mitigate short channel effects in comparison to the n-type doping. The carefully controlled epitaxial growth of InGaAs and InAs channel layers with Nch <1 × 1017 cm−3 is required to realize superior performance InGaAs TFETs.

A microtranslatome coordinately regulates sodium and potassium currents in the human heart.

Catastrophic arrhythmias and sudden cardiac death can occur with even a small imbalance between inward sodium currents and outward potassium currents, but mechanisms establishing this critical balance are not understood. Here, we show that mRNA transcripts encoding INa and IKr channels (SCN5A and hERG, respectively) are associated in defined complexes during protein translation. Using biochemical, electrophysiological and single-molecule fluorescence localization approaches, we find that roughly half the hERG translational complexes contain SCN5A transcripts. Moreover, the transcripts are regulated in a way that alters functional expression of both channels at the membrane. Association and coordinate regulation of transcripts in discrete 'microtranslatomes' represents a new paradigm controlling electrical activity in heart and other excitable tissues.

InAs Channel Inset Effects on the DC, RF, and Noise Properties of InP pHEMTs

GaInAs/InAs composite channels in InP-based pHEMTs enable wideband and/or low-noise performances because of their superior carrier transport properties. To date, the influence of the InAs inset design details on transistor performance has not been parametrized in the literature. We present a systematic study of the effects of the InAs channel inset thickness on transistor characteristics and cutoff frequencies versus temperature, and on the noise performance at 300 K. The epitaxial layer structures considered here incorporate 2 to 5-nm InAs insets in a fixed total composite channel thickness. All layers exhibit excellent electron mobilities (from 40 200 to 54 800 cm2/Vs at 77 K). Thicker InAs insets improve both the current gain cutoff frequency ( ${f}_{\text {T}}$ ) and the maximum oscillation frequency ( ${f}_{\text {MAX}}$ ). However, they also result in higher gate leakage currents and increased channel impact ionization. 50-nm gate length pHEMTs with a 5-nm InAs inset feature the highest simultaneous ${f}_{\text {T}} / {f}_{\text {MAX}} \ge {390}$ /675 (455/800) GHz at 300 (15) K for a low-noise bias but exhibit the poorest minimum noise figure ${NF}_{\text {MIN}}$ . Whereas higher ${f}_{\text {T}}$ (and/or ${f}_{\text {MAX}}$ ) values have traditionally been associated with improved noise performances, this is no longer the case.

The acute toxic effects of platinum nanoparticles on ion channels, transmembrane potentials of cardiomyocytes in vitro and heart rhythm in vivo in mice.

BackgroundPlatinum nanoparticles (PtNPs) have been considered a nontoxic nanomaterial and been clinically used in cancer chemotherapy. PtNPs can also be vehicle exhausts and environmental pollutants. These situations increase the possibility of human exposure to PtNPs. However, the potential biotoxicities of PtNPs including that on cardiac electrophysiology have been poorly understood.MethodsIon channel currents of cardiomyocytes were recorded by patch clamp. Heart rhythm was monitored by electrocardiogram recording. Morphology and characteristics of PtNPs were examined by transmission electron microscopy, dynamic light scattering and electrophoretic light scattering analyses.ResultsIn cultured neonatal mice ventricular cardiomyocytes, PtNPs with diameters 5 nm (PtNP-5) and 70 nm (PtNP-70) concentration-dependently (10–9 – 10–5 g/mL) depolarized the resting potentials, suppressed the depolarization of action potentials and delayed the repolarization of action potentials. At the ion channel level, PtNPs decreased the current densities of INa, IK1 and Ito channels, but did not affect the channel activity kinetics. In vivo, PtNP-5 and PtNP-70 dose-dependently (3–10 mg/kg, i.v.) decreased the heart rate and induced complete atrioventricular conduction block (AVB) at higher doses. Both PtNP-5 and PtNP-70 (10–9 – 10–5 g/mL) did not significantly increase the generation of ROS and leak of lactate dehydrogenase (LDH) from cardiomyocytes within 5 mins after exposure except that only very high PtNP-5 (10–5 g/mL) slightly increased LDH leak. The internalization of PtNP-5 and PtNP-70 did not occur within 5 mins but occurred 1 hr after exposure.ConclusionPtNP-5 and PtNP-70 have similar acute toxic effects on cardiac electrophysiology and can induce threatening cardiac conduction block. These acute electrophysiological toxicities of PtNPs are most likely caused by a nanoscale interference of PtNPs on ion channels at the extracellular side, rather than by oxidative damage or other slower biological processes.

Channel Characteristics of InAs/AlSb Heterojunction Epitaxy: Comparative Study on Epitaxies with Different Thickness of InAs Channel and AlSb Upper Barrier

Because of the high electron mobility and electron velocity in the channel, InAs/AlSb high electron mobility transistors (HEMTs) have excellent physical properties, compared with the other traditional III-V semiconductor components, such as ultra-high cut-off frequency, very low power consumption and good noise performance. In this paper, both the structure and working principle of InAs/AlSb HEMTs were studied, the energy band distribution of the InAs/AlSb heterojunction epitaxy was analyzed, and the generation mechanism and scattering mechanism of two-dimensional electron gas (2DEG) in InAs channel were demonstrated, based on the software simulation in detail. In order to discuss the impact of different epitaxial structures on the 2DEG and electron mobility in channel, four kinds of epitaxies with different thickness of InAs channel and AlSb upper-barrier were manufactured. The samples were evaluated with the contact Hall test. It is found the sample with a channel thickness of 15 nm and upper-barrier layer of 17 nm shows a best compromised sheet carrier concentration of 2.56 × 1012 cm−2 and electron mobility of 1.81 × 104 cm2/V·s, and a low sheet resistivity of 135 Ω/□, which we considered to be the optimized thickness of channel layer and upper-barrier layer. This study is a reference to further design InAs/AlSb HEMT, by ensuring a good device performance.

InGaSb-on-insulator p-channel metal-oxide-semiconductor field-effect transistors on Si fabricated by direct wafer bonding

InGaSb-on-insulator (InGaSb-OI) and InAs/InGaAs/InAs-on-insulator (InAs/InGaAs-OI) structures have been realized on Si by a direct wafer bonding (DWB) technology using atomic-layer-deposition Al2O3. While strain introduced in InGaSb channel layers grown on InAs can enhance the hole mobility of the Sb-based channel layers, a difficult issue of fabricating InGaSb-OI wafers is to obtain a smooth InGaSb surface, which is mandatory for wafer bonding. In this study, the surface of a 20-nm-thick In0.185Ga0.815Sb channel grown on an InAs (100) substrate and an InAs (2.5 nm)/In0.185Ga0.815Sb (20 nm)/InAs (2.5 nm) channel with a 20-nm-thick GaSb buffer layer grown on an InAs (100) substrate by metal-organic chemical vapor deposition have a root mean square of the surface roughness as low as 0.16 and 0.22 nm, respectively, over a scan area of 10 × 10 μm2, which are smooth enough to employ the wafer bonding. As a result, the fabrication of the InGaSb-OI wafers by the DWB and the operation of InGaSb-OI p-channel metal-oxide-semiconductor field-effect transistors (p-MOSFETs) by using the DWB wafers are demonstrated. Also, the performance of InGaSb-OI p-MOSFETs is found to be improved by inserting ultrathin InAs layers between InGaSb and insulating buried oxide layers. An InGaSb-OI and an InAs/InGaAs-OI p-MOSFET under the accumulation-mode operation exhibit a peak mobility of ∼161 and ∼273 cm2/V s, respectively. The channel hole mobility of the InGaSb-OI p-MOSFET is higher than that of the GaSb-on-insulator (GaSb-OI) p-MOSFET and can exceed that of Si p-MOSFETs.

Nucleoporin 107 facilitates the nuclear export of Scn5a mRNA to regulate cardiac bioelectricity.

Nucleoporins (Nups) are known to be functional in nucleo‐cytoplasmic transport, but the roles of nucleoporins in nonproliferating cells, such as cardiac myocytes, are still poorly understood. In this study, we report that Nup107 regulates cardiac bioelectricity by controlling the nucleo‐cytoplasmic trafficking of Scn5a mRNA. Overexpression of Nup107 induced the protein expression of Scn5a rather than that of other ion channels, with no effects of their mRNA levels. The analysis for the protein production demonstrated Nup107‐facilitated transport of Scn5a mRNA. Using RIP‐PCR and luciferase assay, we found that the 5′‐UTR of Scn5a mRNA was not involved in the interaction, whereas the spatial interaction between Nup107 protein and Scn5a mRNA was formed when Scn5a mRNA passing through the nuclear pore. Functionally, Nup107 overexpression in neonatal rat ventricle myocytes significantly increased the currents of Scn5a‐encoded INa channel. Moreover, the close correlation between Nup107 and Nav1.5 protein expression was observed in cardiomycytes and heart tissues subjected to hypoxia and ischaemic insults, suggesting a fast regulation of Nup107 on Nav1.5 channel in cardiac myocytes in a posttranscriptional manner. These findings may provide insights into the emergent control of cardiac electrophysiology through Nup‐mediated modulation of ion channels.

Bottom-up fabrication of InAs-on-nothing MOSFET using selective area molecular beam epitaxy

In this paper we report on the fabrication and electrical characterization of InAs-on-nothing metal-oxide-semiconductor field-effect transistor composed of a suspended InAs channel and raised InAs n+ contacts. This architecture is obtained using 3D selective and localized molecular beam epitaxy on a lattice mismatched InP substrate. The suspended InAs channel and InAs n+ contacts feature a reproducible and uniform shape with well-defined 3D sidewalls. Devices with 1 μm gate length present a saturation drain current (IDsat) of 300 mA mm−1 at VDS = 0.8 V and a trans-conductance (GM) of 120 mS mm−1 at VDS = 0.5 V. In terms of electrostatic control, the devices display a minimal subthreshold swing of 110 mV dec−1 at VDS = 0.5 V and a small drain induced barrier lowering of 50 mV V−1.

Using Light to Endow Stem-Cell-Derived Cardiomyocytes With Virtual IK1 Conductances

Using Light to Endow Stem-Cell-Derived Cardiomyocytes With Virtual IK1 Conductances

Investigating Polycrystalline III-V Thin Films As Channel Materials for “Above IC” Logic and Memory Applications

As conventional semiconductor devices approach the limit of dimensional scaling, the hardware underpinning Information and Communication Technologies is entering an exciting new phase where further increases in integration density will depart from conventional scaling approaches. Future integrated circuits for high performance systems would benefit greatly from a practical realisation of heterogeneous 3D integration, where memory is interleaved with logical computation layers [1]. This approach has the potential for significant gains in energy efficiency, area, and performance. To realise these potential benefits requires the development of semiconductor switches fabricated at temperatures low enough for ‘above IC’ applications, which generally limits processing (on time scales from minutes to hours) to temperatures < 450℃. As dopant activation is typically the highest temperature in a transistor process, this points to semiconductor material systems where dopant activation is not required. In the case of certain III-V and III-N semiconductors, a high density free carrier concentration is present on the surface, with no intentional doping and no activation annealing. For example, it is known that InAs exhibits a high surface electron sheet density (1012-1013cm-2) even in the absence of intentional n-type doping or any thermal annealing for activation [2]. In this work we report on research activities exploring if this high electron concentration can be exploited for above IC device applications. The electronic and structural properties of InAs and Al doped InAs deposited by chemical vapour deposition (CVD) on SiO2/Si and glass substrates at temperatures ≤ 475℃ are reported, with a view to their application as low temperature formed n and p channel transistors which could be integrated in the traditionally passive back-end-of-line metallization of integrated circuits. Figure 1(a) shows the electron mobility and carrier concentration obtained for a nominally undoped polycrystalline (poly) InAs layer (~35nm) on glass formed by CVD at 475℃. The poly-InAs layer demonstrates a high electron concentration in the 6-8x1018 cm-3 range. The carrier type is electrons, with a mobility value around 100 cm2/Vs, which is almost independent of temperature from 125K to 400K, indicating the electron mobility is limited by surface roughness. It is noted that poly-GaAs films demonstrate measured electron mobility values of 0.14 cm2/Vs and measured carrier concentration of 1.3x1016 cm-3. Moving to poly-InAs, the carrier concentration increases to values in the 1018 cm-3 range, with electron mobility values typically from 20-100 cm2/Vs. Forming InAlAs/InAs/InAlAs heterostructures (T< 475℃) results in electron mobility values which are consistently above 100cm2/Vs. If we consider the devices to be embedded within upper metal layers of the IC, then a simplest device architecture would be to utilize the thin InAs channel in a junctionless device architecture [3]. This may require control of the electron concentration to ensure full InAs charge depletion for a high Ion/Ioff ratio. Figure 1(b) demonstrates how the InAs electron concentration can be controlled through Zn incorporation. Moreover, the InAs can be inverted to a p-type semiconductor with increasing Zn flux. Initial hole mobility values around 5 cm2/Vs have been achieved (see Figure 1(c)), demonstrating the potential of this approach for low temperature (T≤ 475℃) formed complementary n and p channel semiconductors for logic or memory (select transistor or SRAM) devices above IC. Figure 1(d) shows a functioning top gated n-channel MOSFET formed on a composite InAs (nominal thickness = 10nm)/GaAs (nominal thickness = 25nm) channel on glass. The device Ion/Ioff ratio is 100. The largest value obtained for the Ion/Ioff ratio to date is ~800. Work is on-going to introduce Al into the InAs channel to increase the energy gap, with the view to achieve higher Ion/Ioff ratios. The presentation will include results from XPS to analyse the % Al incorporation and how this addition of aluminium impacts the carrier mobility and MOSFET behaviour. Finally, it is noted that there is considerable scope for innovation in III-V heterostructure design for optimising device performance, as the spectrum of options is extensive, and epitaxy is not required. In addition, low temperature devices with high electron mobility could be of interest to logic and display technology on flexible substrates. [1] Wong et al., Nature Nanotechnology 10, 191 (2015) [2] Weber, J. R. et al., Appl. Phys. Lett. 97, 192106 (2010) [3] Colinge, J.P. et al., Nature Nanotechnology 5, 225-229 (2010) Figure 1