Showing papers by "Tyndall National Institute published in 2012"
TL;DR: In this article, a range of routes to semiconductor nanowire production have opened up as a result of advances in nanowires fabrication techniques over the last number of decades.
Abstract: Semiconductor nanowires have been the subject of intensive research investment over the past few decades. Their physical properties afford them applications in a vast network of active microelectronic research fields, including logic device scaling in very large scale integrated circuits, sensor devices, and energy harvesting. A range of routes to semiconductor nanowire production have opened up as a result of advances in nanowire fabrication techniques over the last number of decades. These nanowire fabrication routes can usually be categorized into one of two paradigms, bottom-up or top-down. Microelectronic systems typically rely on integrated device platforms, where each device and component thereof can be individually addressed. This requirement for precise addressability places significant demands on the mode of fabrication, specifically with regard to device definition, placement and density, which have typically been strengths of top-down fabrication processes. However, in recent years, advances i...
294 citations
TL;DR: In this article, the authors present a detailed review of integrated magnetics technologies, primarily microinductors, a key component in realizing a monolithic power converter, and propose the use of two performance metrics or figures of merit in order to compare the dc and ac performance of individual microinductor structures.
Abstract: This paper reviews the current state of power supply technology platforms and highlights future trends and challenges toward realizing fully monolithic power converters. This paper presents a detailed survey of relevant power converter technologies, namely power supply in package and power supply on chip (PwrSoC). The performance of different power converter solutions reported in the literature is benchmarked against existing commercial products. This paper presents a detailed review of integrated magnetics technologies, primarily microinductors, a key component in realizing a monolithic power converter. A detailed review and comparison of different microinductor structures and the magnetic materials used as inductor cores is presented. The deposition techniques for integrating the magnetic materials in the microinductor structures are discussed. This paper proposes the use of two performance metrics or figures of merit in order to compare the dc and ac performance of individual microinductor structures. Finally, the authors discuss future trends, key challenges, and potential solutions in the realization of the “holy grail” of monolithically integrated power supplies (PwrSoC).
280 citations
TL;DR: The realization of GaAs lasers on a silicon substrate using a print transfer process offers an alternative wafer-bonding technique for the hybrid integration of optoelectronics.
Abstract: The realization of GaAs lasers on a silicon substrate using a print transfer process offers an alternative wafer-bonding technique for the hybrid integration of optoelectronics.
235 citations
TL;DR: In this article, the effects of spin-orbit-splitting energy on the dominant Auger recombination loss mechanism were investigated for high-mismatched semiconductor alloys such as GaInNAs and GaBiAs.
Abstract: Highly mismatched semiconductor alloys such as GaNxAs1 − x and GaBixAs1 − x have several novel electronic properties, including a rapid reduction in energy gap with increasing x and also, for GaBiAs, a strong increase in spin-orbit-splitting energy with increasing Bi composition. We review here the electronic structure of such alloys and their consequences for ideal lasers. We then describe the substantial progress made in the demonstration of actual GaInNAs telecommunication (telecom) lasers. These have characteristics comparable to conventional InP-based devices. This includes a strong Auger contribution to the threshold current. We show, however, that the large spin-orbit-splitting energy in GaBiAs and GaBiNAs could lead to the suppression of the dominant Auger recombination loss mechanism, finally opening the route to efficient temperature-stable telecomm and longer wavelength lasers with significantly reduced power consumption.
156 citations
TL;DR: In this paper, the electronic structure of GaNAs and GaBiAs has been reviewed and their consequences for ideal lasers have been discussed, and substantial progress has been made in the demonstration of actual GaInNAs telecomm lasers.
Abstract: Highly mismatched semiconductor alloys such as GaNAs and GaBiAs have several novel electronic properties, including a rapid reduction in energy gap with increasing x and also, for GaBiAs, a strong increase in spin orbit- splitting energy with increasing Bi composition. We review here the electronic structure of such alloys and their consequences for ideal lasers. We then describe the substantial progress made in the demonstration of actual GaInNAs telecomm lasers. These have characteristics comparable to conventional InP-based devices. This includes a strong Auger contribution to the threshold current. We show, however, that the large spin-orbit-splitting energy in GaBiAs and GaBiNAs could lead to the suppression of the dominant Auger recombination loss mechanism, finally opening the route to efficient temperature-stable telecomm and longer wavelength lasers with significantly reduced power consumption.
147 citations
TL;DR: The biosynthesis mechanism of gold nanoparticles (AuNPs) in the fungus Rhizopus oryzae is described, showing that at higher Au(III) concentrations, both mycelial and protein yield decrease and damages to the cellular ultrastructure are observed, likely due to the toxic effect of Au( III).
Abstract: In recent years, there has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of gold biomineralization in microorganisms of industrial relevance remains largely unexplored. Here we describe the biosynthesis mechanism of gold nanoparticles (AuNPs) in the fungus Rhizopus oryzae . Reduction of AuCl(4)(-) [Au(III)] to nanoparticulate Au(0) (AuNPs) occurs in both the cell wall and cytoplasmic region of R. oryzae . The average size of the as-synthesized AuNPs is ~15 nm. The biomineralization occurs through adsorption, initial reduction to Au(I), followed by complexation [Au(I) complexes], and final reduction to Au(0). Subtoxic concentrations (up to 130 μM) of AuCl(4)(-) in the growth medium increase growth of R. oryzae and induce two stress response proteins while simultaneously down-regulating two other proteins. The induction increases mycelial growth, protein yield, and AuNP biosynthesis. At higher Au(III) concentrations (>130 μM), both mycelial and protein yield decrease and damages to the cellular ultrastructure are observed, likely due to the toxic effect of Au(III). Protein profile analysis also confirms the gold toxicity on R. oryzae at high concentrations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis shows that two proteins of 45 and 42 kDa participate in gold reduction, while an 80 kDa protein serves as a capping agent in AuNP biosynthesis.
139 citations
TL;DR: Methods of coating live recombinant adenovirus and modified vaccinia virus Ankara (MVA) vectors onto solid microneedle arrays successfully resulted in virus delivery, transcutaneous infection and induced an antibody or CD8(+) T cell response in mice that was comparable to that obtained by needle-and-syringe intradermal immunization.
136 citations
TL;DR: Bulk quantities of graphene nanosheets and nanodots have been selectively fabricated by mechanical grinding exfoliation of natural graphite in a small quantity of ionic liquids, which are solvent free with low levels of naturally absorbed oxygen, inherited from the starting graphite.
136 citations
TL;DR: This is the first demonstration that MNs created from amorphous sugar glasses can be used for incorporating and delivering molecules, and potentially biologically active macromolecules, via the transdermal route.
115 citations
TL;DR: In this article, a drain current model for triple-gate n-type junctionless nanowire transistors is proposed based on the solution of the Poisson equation, which is validated using 3-D TCAD simulations where the drain current and its derivatives, the potential, and the charge density have been compared, showing a good agreement for all parameters.
Abstract: This paper proposes a drain current model for triple-gate n-type junctionless nanowire transistors. The model is based on the solution of the Poisson equation. First, the 2-D Poisson equation is used to obtain the effective surface potential for long-channel devices, which is used to calculate the charge density along the channel and the drain current. The solution of the 3-D Laplace equation is added to the 2-D model in order to account for the short-channel effects. The proposed model is validated using 3-D TCAD simulations where the drain current and its derivatives, the potential, and the charge density have been compared, showing a good agreement for all parameters. Experimental data of short-channel devices down to 30 nm at different temperatures have been also used to validate the model.
93 citations
TL;DR: The enhanced functionality affordable by inclusion of metallic materials as part of nanoengineered particles provides a wealth of new opportunity for innovation and new, more effective, and safer therapeutics for applications such as cancer and cardiovascular diseases.
Abstract: Nanoparticles (NPs) comprised of nanoengineered complexes are providing new opportunities for enabling targeted delivery of a range of therapeutics and combinations. A range of functionalities can be included within a nanoparticle complex, including surface chemistry that allows attachment of cell-specific ligands for targeted delivery, surface coatings to increase circulation times for enhanced bioavailability, specific materials on the surface or in the nanoparticle core that enable storage of a therapeutic cargo until the target site is reached, and materials sensitive to local or remote actuation cues that allow controlled delivery of therapeutics to the target cells. However, despite the potential benefits of NPs as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of NP materials, as well as their size and shape. The need to validate each NP for safety and efficacy with each therapeutic compound or combination of therapeutics is an enormous challenge, which forces industry to focus mainly on those nanoparticle materials where data on safety and efficacy already exists, i.e., predominantly polymer NPs. However, the enhanced functionality affordable by inclusion of metallic materials as part of nanoengineered particles provides a wealth of new opportunity for innovation and new, more effective, and safer therapeutics for applications such as cancer and cardiovascular diseases, which require selective targeting of the therapeutic to maximize effectiveness while avoiding adverse effects on non-target tissues.
TL;DR: In this paper, the potential of power electronics for energy savings in four major application fields, buildings and lighting, power supplies, smart electricity grid, and industrial drives, is investigated.
Abstract: Power electronics is a key technology for the efficient conversion, control, and conditioning of electric energy from the source to the load. In this paper, the potential of power electronics for energy savings in four major application fields, buildings and lighting, power supplies, smart electricity grid, and industrial drives, is investigated. It is shown that by wider adoption of power electronics in these areas, the current European Union electricity consumption could be reduced by 25%. The technology challenges for exploiting this potential for all the four areas are identified in the paper.
TL;DR: In this article, the effect of varying the cladding-core radius ratio on the LP 11 adiabatic criterion is modeled, and a Laguerre-Gaussian beam is created in free space using a spatial light modulator (SLM) and coupled to a few-mode fiber.
TL;DR: It is proved that microneedles based dry electrodes seem to be a promising alternative to standard wet electrodes for the recording of biosignals in clinical examinations and have performance comparable to wet electrodes in recording EEG, EMG and static ECG signals.
Abstract: Monitoring biosignals, such as in electrocardiography (ECG), electromiography (EMG) and electroencephalography (EEG), is important for a better understanding of the pathological and physiological conditions of human subjects. In clinical practice the recording of biopotentials is carried out in general with wet electrodes, considered as the golden standard, although they have shown some limits: (i) the susceptibility to motions artifacts, critical aspect in ECG and EMG monitoring, (ii) the time-consuming procedure to be applied in EEG examinations, and (iii) the inability to record biosignals in long-term applications. In the past years innovative solutions have been suggested, among which microstructured dry electrodes showed very promising features. This study represents a first technological assessment of a novel type of microneedles-based dry electrodes. In this paper it has been proved that these electrodes: (i) seem to allow a better electro-mechanical interface with human skin, (ii) have performance comparable to wet electrodes in recording EEG, EMG and static ECG signals, showing an improvement in the monitoring of ECG signal in dynamic conditions, and (iii) do not need the long-lasting skin preparation as wet electrodes for EEG applications, appearing easy to use and to apply. In conclusion, our microneedles based dry electrodes seem to be a promising alternative to standard wet electrodes for the recording of biosignals in clinical examinations.
TL;DR: In this article, a solution-phase assembly of alkane-amine layers is presented for non-covalent functionalization of graphene based on solution phase assembly of 1-aminodecane molecules.
Abstract: A simple, versatile method for non-covalent functionalization of graphene based on solution-phase assembly of alkane-amine layers is presented. Second-order Moller–Plesset (MP2) perturbation theory on a cluster model (methylamine on pyrene) yields a binding energy of ≈220 meV for the amine–graphene interaction, which is strong enough to enable formation of a stable aminodecane layer at room temperature. Atomistic molecular dynamics simulations on an assembly of 1-aminodecane molecules indicate that a self-assembled monolayer can form, with the alkane chains oriented perpendicular to the graphene basal plane. The calculated monolayer height (≈1.7 nm) is in good agreement with atomic force microscopy data acquired for graphene functionalized with 1-aminodecane, which yield a continuous layer with mean thickness ≈1.7 nm, albeit with some island defects. Raman data also confirm that self-assembly of alkane-amines is a non-covalent process, i.e., it does not perturb the sp2 hybridization of the graphene. Passivation and adsorbate n-doping of graphene field-effect devices using 1-aminodecane, as well as high-density binding of plasmonic metal nanoparticles and seeded atomic layer deposition of inorganic dielectrics using 1,10-diaminodecane are also reported.
TL;DR: In this article, the fabrication of a novel ultrasharp silicon microneedle array for use as a physiological signal monitoring electrode is described, which uses double-sided silicon wafer patterning and anisotropic potassium hydroxide wet etching to simultaneously create a micro-drone on the front side of the wafer, and a through-silicon via from the backside.
Abstract: The fabrication of a novel ultrasharp silicon microneedle array for use as a physiological signal monitoring electrode is described. This work uses double-sided silicon wafer patterning and anisotropic potassium hydroxide wet etching to simultaneously create a microneedle on the front side of the wafer, and a through-silicon via from the backside. Metal deposition on both the front and the back of the wafer then establishes electrical contact through this via between both sides of the electrode. This technique eliminates the limitations associated with other approaches that are used to create front-to-back electrical contact and that may be slow or cumbersome. Wearable electrode prototypes have been assembled using these arrays, and electrocardiography (ECG) and electromyography (EMG) recordings have been carried out to verify the functionality of the technique.
TL;DR: In this article, surface engineering of silicon nanocrystals directly in water or ethanol by atmospheric pressure dc microplasma is reported, which induces non-equilibrium liquid chemistry that passivates the silicon nanoparticles surface with oxygen-/organic-based terminations.
Abstract: Surface engineering of silicon nanocrystals directly in water or ethanol by atmospheric-pressure dc microplasma is reported. In both liquids, microplasma processing stabilizes the optoelectronic properties of silicon nanocrystals. The microplasma treatment induces non-equilibrium liquid chemistry that passivates the silicon nanocrystals surface with oxygen-/organic-based terminations. In particular, the microplasma treatment in ethanol drastically enhances the silicon nanocrystals photoluminescence intensity and causes a clear red-shift (�80 nm) of the photoluminescence maximum. The photoluminescence properties are stable after several days of storage in either ethanol or water. The surface chemistry induced by the microplasma treatment is analyzed and discussed.
TL;DR: In this article, a new and low cost facile technique has been reported to fabricate coaxial nickel oxide/nickel (NiO/Ni) nanowire (NW) arrays as high performance electrodes for pseudocapacitors.
TL;DR: The modification of self-assembled monolayers (SAMs) on gold electrode surface with 11-mercaptoundecanoic acid (11-MUA) is described, with acceptable reproducibility and good stability, with a wide linear response to BaP.
Abstract: Well-oriented bio-conjugates on gold electrode surfaces will indirectly influence the molecular recognition of antigens to surface bound antibodies thus improving the detection performance of electrochemical immunosensors This paper describes the modification of self-assembled monolayers (SAMs) on gold electrode surface with 11-mercaptoundecanoic acid (11-MUA) Activation of carboxylic acid terminal was performed by reaction of a mixture of water soluble carbodiimide and N-hydrosuccinimide (NHS) on the electrode surfaces Characterisation of the SAM formation on the gold electrode was performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and contact angle measurements An amperometric immunosensor was developed for the screening of polycyclic aromatic hydrocarbons (PAHs) in water The system consists of gold as the working electrode, platinum as the counter electrode and a Ag/AgCl reference electrode This three electrode system is integrated on a single chip The measurement employs the enzyme-linked immunosorbent assay (ELISA) principle Benzo[a]pyrene (BaP) was detected using an immunological reaction by measuring the alkaline phosphatase (AP) enzymatic reaction towards the substrate para-amino phenyl phosphate (pAPP) A competitive assay was performed within the electrode using AP as the labelled-enzyme A lower limit of detection (56 ng ml−1) of BaP was achieved after the activation of the mixture of carbodiimide and succinimide with the alkanethiol SAM on the gold electrode in comparison to that obtained for the unmodified electrode (142 ng ml−1) The developed surface functionalised sensor demonstrated acceptable reproducibility and good stability, with a wide linear response to BaP (4–140 ng ml−1)
TL;DR: The merits and limitations of balloon angioplasty and stent implantation, the most common treatment options for CAD, and the pathophysiology associated with these treatments are discussed.
Abstract: Coronary artery disease (CAD) kills millions of people every year. It results from a narrowing of the arteries (stenosis) supplying blood to the heart. This review discusses the merits and limitations of balloon angioplasty and stent implantation, the most common treatment options for CAD, and the pathophysiology associated with these treatments. The focus of the review is heavily placed on research efforts geared toward the modification of stent surfaces for the improvement of stent-vascular compatibility and the reduction in the occurrence of related pathophysiologies. Such modifications may be chemical or physical, both of which are surveyed here. Chemical modifications may be passive or active, while physical modification of stent surfaces can also provide suitable substrates to manipulate the responses of vascular cells (endothelial, smooth muscle, and fibroblast). The influence of micro- and nanostructured surfaces on the in vitro cell response is discussed. Finally, future perspectives on the combination of chemical and physical modifications of stent surfaces are also presented. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
TL;DR: It is envisioned that such a controllable process, combined with the precision patterning of the aligned block copolymer nanopatterns, could prolong the scaling of nanoelectronics and potentially enable the fabrication of dense, parallel arrays of multi-gate field effect transistors.
Abstract: Extending the resolution and spatial proximity of lithographic patterning below critical dimensions of 20 nm remains a key challenge with very-large-scale integration, especially if the persistent scaling of silicon electronic devices is sustained. One approach, which relies upon the directed self-assembly of block copolymers by chemical-epitaxy, is capable of achieving high density 1 : 1 patterning with critical dimensions approaching 5 nm. Herein, we outline an integration-favourable strategy for fabricating high areal density arrays of aligned silicon nanowires by directed self-assembly of a PS-b-PMMA block copolymer nanopatterns with a L0 (pitch) of 42 nm, on chemically pre-patterned surfaces. Parallel arrays (5 × 106 wires per cm) of uni-directional and isolated silicon nanowires on insulator substrates with critical dimension ranging from 15 to 19 nm were fabricated by using precision plasma etch processes; with each stage monitored by electron microscopy. This step-by-step approach provides detailed information on interfacial oxide formation at the device silicon layer, the polystyrene profile during plasma etching, final critical dimension uniformity and line edge roughness variation nanowire during processing. The resulting silicon-nanowire array devices exhibit Schottky-type behaviour and a clear field-effect. The measured values for resistivity and specific contact resistance were ((2.6 ± 1.2) × 105 Ωcm) and ((240 ± 80) Ωcm2) respectively. These values are typical for intrinsic (un-doped) silicon when contacted by high work function metal albeit counterintuitive as the resistivity of the starting wafer (∼10 Ωcm) is 4 orders of magnitude lower. In essence, the nanowires are so small and consist of so few atoms, that statistically, at the original doping level each nanowire contains less than a single dopant atom and consequently exhibits the electrical behaviour of the un-doped host material. Moreover this indicates that the processing successfully avoided unintentional doping. Therefore our approach permits tuning of the device steps to contact the nanowires functionality through careful selection of the initial bulk starting material and/or by means of post processing steps e.g. thermal annealing of metal contacts to produce high performance devices. We envision that such a controllable process, combined with the precision patterning of the aligned block copolymer nanopatterns, could prolong the scaling of nanoelectronics and potentially enable the fabrication of dense, parallel arrays of multi-gate field effect transistors.
TL;DR: Highly dense hexagonal ordered arrays of superparamagnetic iron oxides nanodots are fabricated by a simple and cost-effective route and show good thermal stability and strong adherence to the substrate surface, making them useful for practical device applications.
Abstract: Highly dense hexagonal ordered arrays of superparamagnetic iron oxides nanodots are fabricated by a simple and cost-effective route. Spectroscopic, microscopic and magnetic measurements show that the nanodots have uniform size, shape and their placement mimics the original self-assembled block copolymer pattern. The nanodots show good thermal stability and strong adherence to the substrate surface, making them useful for practical device applications.
TL;DR: In this article, a hybrid NiNWA/PdNF (nanoflowers) electrocatalyst with high electrocatalytic performance for the electrooxidation of ethanol in alkaline media has been fabricated by borohydride hydrothermal reduction method.
TL;DR: The use of III-V materials as the channel in future transistor devices is dependent on removing the deleterious native oxides from their surface before deposition of a gate dielectric.
Abstract: The use of III–V materials as the channel in future transistor devices is dependent on removing the deleterious native oxides from their surface before deposition of a gate dielectric. Trimethylaluminium has been found to achieve in situ “clean-up” of the oxides of GaAs and InGaAs before atomic layer deposition (ALD) of alumina. Here we propose seven reaction mechanisms for “clean-up”, featuring exchange of ligands between surface atoms, reduction of arsenic oxide by methyl groups, and desorption of various products. We use first-principles density functional theory (DFT) to determine which mechanistic path is thermodynamically favored. We also discuss the statistical likelihood of the interdependent pathways. “Clean-up” of an oxide film is shown to strongly depend on electropositivity of the precursor metal, affinity of the precursor ligand to the oxide, and the redox character of the oxide. The predominant pathway for a metalloid oxide such as arsenic oxide is reduction, producing volatile molecules or ...
TL;DR: An analytical limitation on the use of time-delayed feedback control for the stabilization of periodic orbits in autonomous systems is proved, and it is shown that this limitation correctly predicts the stability boundaries in this case.
Abstract: We prove an analytical limitation on the use of time-delayed feedback control for the stabilization of periodic orbits in autonomous systems. This limitation depends on the number of real Floquet multipliers larger than unity, and is therefore similar to the well-known odd number limitation of time-delayed feedback control. Recently, a two-dimensional example has been found, which explicitly demonstrates that the unmodified odd number limitation does not apply in the case of autonomous systems. We show that our limitation correctly predicts the stability boundaries in this case.
TL;DR: In this paper, the authors demonstrate a facile, generic method for the fabrication of highly dense long range hexagonally ordered various inorganic oxide nanodots on different substrates by using a microphase separated polystyrene-b-poly(ethylene oxide) block copolymer (BCP) thin film as a structural template.
Abstract: We demonstrate a facile, generic method for the fabrication of highly dense long range hexagonally ordered various inorganic oxide nanodots on different substrates by using a microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin film as a structural template. The method does not require complex co-ordination chemistry (between metal precursors and the polymer) and instead involves the simple, solution based chemistry applicable to a wide range of systems. A highly ordered PS-b-PEO thin film with perpendicularly oriented PEO cylinders is fabricated by solvent annealing over wafer scale. PEO cylinders are activated by ethanol to create a functional chemical pattern for nanodot development via spin coating and block selective metal ion inclusion. Subsequent UV/ozone treatment forms an ordered arrangement of oxide nanodots and removes the polymer components. The phase purity, crystallinity and thermal stability of these materials coupled to the ease of production may make them useful in technological applications. This method is particularly useful because the feature sizes can be tuned by changing the concentration of the precursors without changing the molecular weight and concentration of the block copolymer.
TL;DR: Frequency division multiplexing/frequency division multi-access passive optical networks are shown to provide a possible solution in terms of performance, manufacturability and cost to the specification of the second next generation passive optical access systems (NG-PON2).
Abstract: Frequency division multiplexing/frequency division multi-access passive optical networks are shown to provide a possible solution in terms of performance, manufacturability and cost to the specification of the second next generation passive optical access systems (NG-PON2). The upstream capacity of a particular implementation is experimentally evaluated, and the implementation of the required optical network unit in silicon photonics is analyzed, as this complementary-metal-oxide-semiconductor-compatible technology is well suited for mass market applications.
TL;DR: It is demonstrated that on the length scale on which the semimetal-semiconductor transition occurs, this enables the use of bandgap engineering to form a field-effect transistor near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain.
Abstract: Energy bandgaps are observed to increase with decreasing diameter due to quantum confinement in quasi-one-dimensional semiconductor nanostructures or nanowires. A similar effect is observed in semimetal nanowires for sufficiently small wire diameters: A bandgap is induced, and the semimetal nanowire becomes a semiconductor. We demonstrate that on the length scale on which the semimetal-semiconductor transition occurs, this enables the use of bandgap engineering to form a field-effect transistor near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain. By removing the requirement to supply free carriers by introducing dopant impurities, quantum confinement allows for a materials engineering to overcome the primary obstacle to fabricating sub-5 nm transistors, enabling aggressive scaling to near atomic limits.
TL;DR: In this paper, the effect of forming gas annealing on surface-channel In0.53 Ga0.47As MOSFETs with atomic-layer-deposited Al2O3 as the gate dielectric was investigated.
Abstract: We investigated the effect of forming gas (5% H2/95% N2) annealing on surface-channel In0.53 Ga0.47As MOSFETs with atomic-layer-deposited Al2O3 as the gate dielectric. We found that a forming gas anneal (FGA) at 300°C for 30 min was efficient at removing or passivating positive fixed charges in Al2O3 , resulting in a shift of the threshold voltage from -0.63 to 0.43 V and in an increase in the Ion/Ioff ratio of three orders of magnitude. Following FGA, the MOSFETs exhibited a subthreshold swing of 150 mV/dec, and the peak transconductance, drive current, and peak effective mobility increased by 29%, 25%, and 15%, respectively. FGA significantly improved the source- or drain-to-substrate junction isolation, with a reduction of two orders of magnitude in the reverse bias leakage exhibited by the Si-implanted In0.53Ga0.47As n+/p junctions, which is consistent with passivation of midgap defects in In0.53Ga0.47As by the FGA process.
Proceedings Article•
01 May 2012TL;DR: In this paper, the physics and basic properties of junctionless transistors are described and compared to devices with junctions, including excellent sub-threshold slope and DIBL, and they are shown to be less subject to short-channel effects than devices with junction.
Abstract: This paper describes the physics and basic properties of junctionless transistors. These FETs are less subject to short-channel effects than devices with junctions, including excellent subthreshold slope and DIBL.