bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact Model for Nano-Wire Tunnel Field-Effect Transistor
Authors: Sato Shingo , Omura Yasuhisa , Mallik Abhijit
Published: May 2015

This paper presents a compact model of the Nano-Wire Tunnel Field-Effect Transistor (NW-TFET). We analyze the validity of the previous-reported transmission probability and our model using an analytical potential model with a depletion approximation. We clarify the difference between the models by using the ratio of channel length to natural length to characterize the NW-TFET. By considering the offset of the gate voltage, the tunnel probability of our model can reproduce the numerically derived one for any channel length near the on-state. Finally, we present a compact model of the drain current.
Study of Hysteresis in Vertical Ge-Source Heterojunction Tunnel-FETs at Low Temperature
Authors: Neves Felipe Souza , Agopian Paula Ghedini Der , Martino Joao Antonio , Vandooren Anne , Rooyackers Rita , Simoen Eddy , Thean Aaron , Claeys Cor
Published: May 2015

This work studies the hysteresis behaviour in vertical Ge-source gate all-around tunnel field-effect transistors (TFETs) at low temperature. Two devices with different HfO2 thickness in the gate stack (2nm and 3nm) are compared. The goal is to investigate the impact of oxide trapping on the trap-assisted tunneling. It is shown that there is only a minor effect – the main impact of gate oxide trapping is the shift in the onset voltage of the TFET, through a charge-trapping-induced shift in the flat-band voltage.
Vertical Nanowire TFET Diameter Influence on Intrinsic Voltage Gain for Different Inversion Conditions
Authors: Sivieri Victor De Bodt , Bordallo Caio Cesar Mendes , Agopian Paula Ghedini Der , Martino Joao Antonio , Rooyackers Rita , Vandooren Anne , Simoen Eddy , Thean Aaron , Claeys Cor
Published: May 2015

In this work, the impact of the nanowire TFET diameter on analog parameters in “weak” and “strong inversion” conditions is analyzed. Its relation with the current conduction mechanism is also studied. A comparison of the analog performance among TFETs doped with different source doping profile (abrupt and non-abrupt) and MOSFETs was experimentally realized for larger diameter nanowires. Additionally the TFET evaluation was extrapolated for smaller diameters by numerical simulation. The transistor efficiency and the Early voltage were considered in order to calculate the intrinsic voltage gain (AV). Both effects influence AV degradation for TFETs with smaller diameters biased in “weak inversion”. While larger TFET nanowires show better AV than MOSFETs under “strong inversion” bias, narrower nanowires present potentialities for low power and low voltage applications, since their AV is better than the corresponding values for larger diameters TFET nanowires under “weak inversion” bias.
Analytically Modeling the Asymmetric Double Gate Tunnel FET
Authors: Lv Hongfei , Sato Shingo , Omura Yasuhisa , Mallik Abhijit
Published: May 2015

This paper proposes an analytical model for the asymmetric double gate (ADG) TFET. The two-dimensional Poisson equation is solved based on a depletion approximation. The two-dimensional potential function is given by appropriate boundary conditions. Internal electric field is calculated from the potential model and the tunnel current is numerically calculated using Kane’s tunnel current generation model. We use a commercial TCAD simulator to examine the analytical model.
(Invited) Special Memory Mechanisms in SOI Devices
Authors: Cristoloveanu Sorin , Bawedin Maryline , Navarro Carlos , Chang Sung-Jae , Wan Jing , Andrieu François , Le Royer Cyrille , Rodriguez Noel , Gamiz Francisco , Zaslavsky Alexander , Kim Yong-Tae
Published: May 2015

Several types of floating-body capacitorless 1T-DRAM memory cells with planar SOI or multi-gate configuration are reviewed and compared. We show that 1T-DRAMs are also compatible with the ‘unified memory’ paradigm which aims at combining, within a single SOI transistor, volatile, nonvolatile and multiple-state memory functionalities. We focus on our recently proposed concepts (MSDRAM, A2RAM and Z2-FET), by addressing the device architecture and fabrication, operating mechanisms, and scaling issues. Experimental results together with numerical simulations indicate the directions for performance optimization.
(Invited) Spin-Based Silicon and CMOS-Compatible Devices
Authors: Sverdlov Viktor , Selberherr Siegfried
Published: May 2015

Silicon, the main material of microelectronics, is attractive for extending the functionality of MOSFETs by using the electron spin. However, spin lifetime decay in the silicon-on-insulator transistor channel is a potential threat to spin-driven devices using silicon. We predict a giant enhancement of the electron spin lifetime in silicon thin films by applying uniaxial mechanical stress. The advantage of this proposal is that stress techniques are already routinely used in semiconductor industry to enhance the electron and hole mobility, respectively. The spin manipulation in silicon by purely electrical means is a challenge because of a relatively weak coupling of the electron spin to the electric field through an effective gate voltage dependent spin-orbit interaction. In contrast, the coupling between the spin orientation and charge current is much stronger in magnetic tunnel junctions. Magnetic random access memory (MRAM) built on magnetic tunnel junctions is CMOS-compatible and possesses all properties required for universal memory. We demonstrate a significant improvement of one of the critical MRAM characteristics, the switching time, by specially designing the recording layer. Finally, by using MRAM arrays we discuss a realization of an intrinsic non-volatile logic-in-memory architecture suitable for future low-power electronics.
Variation of Spin Lifetime with Spin Injection Orientation in Strained Thin Silicon Films
Authors: Ghosh Joydeep , Osintsev Dmitry , Sverdlov Viktor , Selberherr Siegfried
Published: May 2015

Spintronics attracts at present much interest because of the potential to build novel spin-based devices which are superior to charge-based microelectronic elements. Silicon, the main element of microelectronics, is promising for spin-driven applications. Understanding the peculiarities of the subband structure and details of spin propagation in thin silicon films in the presence of the spin-orbit interaction is under scrutiny. We show that shear strain has a strong influence in modifying the subband structure and thus can dramatically boost both of the surface roughness and electron-phonon interaction limited spin lifetime in an ultra-thin silicon-on-insulator-based transistor. We also report that a change in the spin injection direction has an impact on the spin lifetime.
Stress Considerations in Thin Films for CMOS-Integrated Gas Sensors
Authors: Filipovic Lado , Selberherr Siegfried
Published: May 2015

The integration of gas sensing elements into hand-held electronics will provide individuals the ability to detect harmful chemicals and pollutants in the environment in real time. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas at an elevated temperature. The intrinsic stress in the metal oxide films during the low-temperature, high-pressure, and low oxygen content sputter deposition of tin oxide (SnO2) and indium-tin-oxide (ITO) is examined in this work. The surface free energy for the two films is found to be 1.69J/m2 and 1.85J/m2, respectively, and the intrinsic stress during the early stages of film growth is plotted. The spray pyrolysis deposition technique is implemented to grow a tin oxide film at 400°C, which is able to detect the presence of multiple gases in the environment. Deposition at this temperature leads to a thermo-mechanical stress of 380MPa.
Geometrical Magnetoresistance in Multi-Gate FDSOI Structures
Authors: Navarro Carlos , Chang Sung-Jae , Bawedin Maryline , Andrieu François , Sagnes Bruno , Cristoloveanu Sorin
Published: May 2015

The geometrical magnetoresistance in advanced planar and 3D multi-gate FDSOI transistors is addressed. The strong dependence of the magnetoresistance mobility on the device architecture, size and magnetic field orientation is analyzed and discussed with the help of numerical simulations.
Low Temperature Atomically Flattening of Si Surface of Shallow Trench Isolation Pattern
Authors: Goto Tetsuya , Kuroda Rihito , Suwa Tomoyuki , Teramoto Akinobu , Akagawa Naoya , Kimoto Daiki , Sugawa Shigetoshi , Ohmi Tadahiro , Kamata Yutaka , Kumagai Yuki , Shibusawa Katsuhiko
Published: May 2015

Low temperature (800 ºC - 900 ºC) Ar annealing for atomically flattening was applied to shallow trench isolation (STI)-patterned wafers where Si and SiO2 coexist on the wafer surface. During the Ar annealing, concentrations of H2O and O2 residual gases in the annealing ambience was maintained at low level less than 30 ppb. Such low temperature and clean Ar ambience can suppress oxidation and etching of Si surface as well as a decomposition of thick SiO2 film for device isolation. As a result, the atomically flat Si surface was obtained for the Si active pattern having STI edge by the Ar annealing at 800 ºC - 900 ºC. Owing to the introduction of the atomically flat Si/gate oxide interface, breakdown characteristic of the fabricated MOS capacitors was improved for the atomically flat devices.
Proton Radiation Effects on the Analog Performance of Bulk n- and p-FinFETs
Authors: Bertoldo Marcelo , Oliveira Alberto Vinícius de , Agopian Paula Ghedini Der , Simoen Eddy , Claeys Cor , Martino Joao Antonio
Published: May 2015

This paper presents an evaluation of the impact of 60 MeV Proton radiation on triple gate Bulk FinFETs, for both n and p types. The main focus is intrinsic voltage gain, threshold voltage and the OFF region drain current. The narrow nFinFET devices present an unexpected degradation of the drain current in the off-state region, which shows that the radiation affects severely the STI oxide resulting in a high parasitic conduction. The pFinFETs are more tolerant than the nFinFETs for environments that suffer from high-energy proton exposure.
Comparison of Current Mirrors Designed with TFET or FinFET Devices for Different Dimensions and Temperatures
Authors: Martino Marcio Dalla Valle , Martino Joao Antonio , Agopian Paula Ghedini Der , Vandooren Anne , Rooyackers Rita , Simoen Eddy , Thean Aaron , Claeys Cor
Published: May 2015

The aim of this work is to compare the suitability of Tunnel-FET and FinFET devices in a basic circuit such as a current mirror. Their performances have been compared in terms of susceptibility to variations in the output transistor dimensions, in bias conditions and in temperature. At first, experimental results showed that both TFETs and FinFETs presented a similar channel width dependence, but the former was much less affected by channel length variations. The output bias condition has been studied as well. Then, simulations expanded the analyses for the temperature impact, showing that the different dominant transport mechanism in each case resulted in opposite trends and susceptibility to the temperature. Therefore, it was observed that TFETs presented better results than FinFETs as components of the highlighted circuit, since the use of TFETs enabled it to mirror the input current even in the case of dimension mismatch and temperature variation.
Impact of Gate Stack Dielectric on Intrinsic Voltage Gain and Low Frequency Noise in Ge pMOSFETs
Authors: Oliveira Alberto Vinícius de , Agopian Paula Ghedini Der , Martino Joao Antonio , Fang Wen , Arimura Hiroaki , Mitard Jerome , Mertens Hans , Simoen Eddy , Mocuta Anda , Collaert Nadine , Thean Aaron , Claeys Cor
Published: May 2015

This paper presents an experimental analysis of the gate stack dielectric influence on low frequency noise and intrinsic voltage gain (AV) in planar germanium pMOSFETs with a HfO2/Al2O3 gate stack. The Av is studied not only at room temperature, but also from 25 to 150 °C. It is observed that neither the HfO2 - thickness nor the plasma oxidation power have a significant impact on the noise power spectral density and intrinsic voltage gain (AV). In contrast, the thinner Al2O3 - layer is more susceptible to any damage during the fabrication processes, which increases the interface state density (NIT) between the Ge surface and gate stack layer, resulting in a device performance degradation. Furthermore, from high temperature point of view, the AV is predominantly dominated by the carrier mobility degradation, which reduces the transconductance.
The Comprehension of the Interfacial Chemistry during Etching Process onto SC: A Way to Understand the Mechanism
Authors: Vayron Tommy , Causier A , Bouttemy Muriel , Gérard Isabelle , Aureau Damien , Vigneron Jacky , Etcheberry Arnaud
Published: May 2015

Etching and electrochemical behaviors of n & p InP are studied in acidic bromine solutions. We observe very similar behaviors as the ones observed for GaAs. Surface analysis performed by XPS detects that very complex oxidation processes are generated at the interface during the etching process. The presence of these oxide phase points out that we have to consider the classical chemical attack proposed in the literature but also electroless contribution which is intimately associated to the global process.
Impact of Surface Texturization on Overall Performance of Mono-Crystalline Silicon Solar Cells
Authors: Sankarasubramanian Shrihari , Saud Gaurav Kumar , Shashikala M , Suratkar Prakash , Saravanan S
Published: May 2015

The surface texturization of silicon wafers is a key process in solar cell manufacturing to minimize reflective loss and thus increase current. The chemical route adopted for surface texturization have practical issues such as non-uniform texture, homogeneous agitation during process and the most importantly the high cost of isopropanol (IPA). In order to eliminate the aforementioned issues the manufacturers use commercially available texture additives for the texture process. In this this study we evaluated two commercial additives to achieve uniform texture and thus reduce the surface reflectance. The studies were carried out on 125 x 125 mm mono-crystalline silicon (C-Si) wafers. The wafer reflectivity and texture uniformity were studied. The wafers were then processed to fabricate solar cells and the I-V characteristics of these cells were evaluated.
Prediction of Photovoltaic Cu(In,Ga)Se2 p-n Device Performance by forward Bias Electrochemical Analysis of Only the p-Type Cu(In,Ga)Se2 Films
Authors: Colombara Diego , Bertram Tobias , Depredurand Valérie , Fouquet Thierry , Bour Jérôme , Broussillou Cédric , Grand Pierre-Philippe , Dale Phillip J.
Published: May 2015

This work is an attempt to rate the quality of Mo/Cu(In,Ga)Se2 films intended for fabrication of photovoltaic devices. The procedure is based on the simple current-voltage electrochemical analysis of the bilayer in a Eu2+/3+-containing electrolyte solution. Two series of bilayer samples were tested electrochemically, while sister samples were completed into Mo/Cu(In,Ga)Se2/CdS/i-ZnO/Al:ZnO/Ni-Al solid state devices and their current-voltage characteristics measured in the dark. A correlation was found between the reverse saturation current density of the solid state devices and an analogous parameter extracted from the electrochemical response in forward bias. While Eu2+ was found to be metastable in water posing restrictions to the application, reproducible measurements were achieved with a methanol-based solution. The intrinsic simplicity of the proposed methodology makes it particularly suitable for the implementation of a low-cost diagnostic tool.
(Invited) Fabrication and Characterization of Silicon Microwire Anodes by Electrochemical Etching Techniques
Authors: Nöhren Sandra , Quiroga-González Enrique , Carstensen Jürgen , Föll Helmut
Published: May 2015

With a technique principally allowing for large scale production based on electrochemical etching, silicon microwires for Li ion battery anodes are produced. Those silicon wires exhibit high cycling stability with high amount of active material which does not degenerate over the cycling period due to the formation of a homogeneous solid electrolyte interface around each wire. This study summarizes the importance of the (exact) battery work parameters and shows the influence of different wire dimensions on the battery performance and cycling stability. Furthermore, it compares two anode variations in which the wires can be incorporated. FFT-impedance analysis shows the characteristic resistance changes under specific conditions, which relate directly to the processes of the wires, allowing to optimize the electrochemical processes.
Pseudocapacitive Charge Storage at Nanoscale Silicon Electrodes
Authors: McSweeney William , Geaney Hugh , Glynn Colm , McNulty David , O'Dwyer Colm
Published: May 2015

Pseudocapacitive behaviour can be accessed when Si nanowire (NW) electrodes are scanned at relatively fast potential scan rates in Li-ion battery electrolytes. Measurements using cyclic voltammetry supported by electron microscopy confirm that Si NWs formed on silicon substrates, as opposed to metallic current collectors, do not solely undergo alloying reactions. The influence of doping type, carrier concentration and bias condition during voltammetric polarization significantly alters the mechanism of electrochemical energy storage. The formation of a carrier depleted (electrically dead) layer of n-type NWs on silicon current collector electrodes limits insertion or alloying processes and rates that ordinarily form Li-Si phases, and charge is also stored within the electric double layer via pseudocapacitive processes. P-type NWs with solid crystalline cores also exhibit pseudocapacitive charge storage without structural modification of the NWs.
Electroless Ni Layer: Influence of Growth Steps and Annealing Temperature on NiSi Formation
Authors: Delbos Elise , El Belghiti Hanane , Aureau Damien , Vigneron Jackie , Bouttemy Muriel , Etcheberry Arnaud
Published: May 2015

For the improvement of the silicon solar cell and competitiveness, one of the today challenges is to process Ni/Cu contact lines by chemical way. The study presented in this article is focused on the annealing of electroless nickel-phosphorous layers to create the NiSi film necessary for the good adhesion of the Ni/Cu stack and to guaranty the low contact resistance of these lines. The impact of the initial Ni-P layer thickness and the annealing temperature were particularly taken into account. Thanks to a combination of characterization techniques (SEM, EDS and XPS), the thickness and the composition of the NiSi layer were well established and monitored enabling to optimize the contact line procedure.
Chemical Nature and Control of High-k Dielectric/III-V Interfaces
Authors: Cabrera Wilfredo J , Halls Mathew D. , Chabal Yves J
Published: May 2015

A number of surface treatments and deposition techniques have been developed to control the interface of high-k/III-V semiconductor gate stacks, which is critical to III-V-based device performance. While electrical measurements have demonstrated the value of these specific processes, there has been little work on the chemical composition of III-V surfaces and interfaces. Using primarily infrared absorption spectroscopy, we have focused on two aspects associated with oxide growth processing: 1) chemical passivation of the interface with monolayer engineering, and 2) barrier for III-V elemental diffusion. We find for example that incorporation of silicon layer by gas phase processing prior to atomic layer deposition of Al2O3 on an oxidized InP surface is effective in reducing an interface layer, composed of dative P=O•••Al and covalent P-O-Al bonds. However, such barriers are not as effective in preventing indium diffusion through high-k dielectrics either during ALD growth or upon post-annealing.
Photoelectrochemical Studies and Capacitance Measurements during the Nitride Passivation of InP in Liquid Ammonia (-55°C)
Authors: Njel Christian , Bakas Idriss , Aureau Damien , Gonçalves Anne-Marie , Etcheberry Arnaud
Published: May 2015

This paper is based on fundamental photo-electrochemical studies of an anodic passivation process at the interface n-InP/liquid ammonia (-55 °C). Thanks to X-ray Photoelectron Spectroscopy analyses, a reproducible polyphosphazene like film was reported on InP (-[(H2N)-P=N]n-). A variation of the interfacial potential close to one volt is observed during the galvanostatic treatment. According to the anodic charge a gradual shift of the flat band potential is revealed while keeping the same slope of the Mott-Shottky straight line. As a consequence the graphical representation of C-2 = f(V) becomes drastically flat and extended over 1 volt. The modification of InP surface leads then to a high interfacial capacitance (≈ 2µF.cm-2). The almost total lack of the photo-potential is another significant consequence of the passivation of InP. These results suggest the accumulation configuration of the modified interface.
(Invited) Measurement of the Energy-Band Relations of Stabilized Si Photoanodes Using Operando Ambient Pressure X-ray Photoelectron Spectroscopy
Authors: Richter Matthias Hermann , Lichterman Michael Frankston , Hu Shu , Crumlin Ethan J , Mayer Thomas , Axnanda S , Favaro Marco , Drisdell Walter , Hussain Z , Brunschwig Bruce , Lewis Nathan S. , Liu Z , Lewerenz Hans Joachim
Published: May 2015

The energy-band relations and electronic properties for the light absorber/protection-layer stack of TiO2-stabilized Si photoanodes have been determined by ambient pressure x-ray synchrotron radiation photoelectron spectroscopy under an applied potential (operando), from single core-level emission lines. The experiments have also been complemented with laboratory-based monochromatic XPS data. Electrochemical parameters are additionally derived directly from x-ray photoemission data, and a method is presented to derive interface-state densities from such operando data.
(Invited) P-Type Transparent Conducting Oxide Protection Layers for Sustainable Photoelectrochemical Water Oxidation
Authors: Chen Le , Yang Jinhui , Lee Lyman , Klaus Shannon , Woods-Robinson Rachel , Lum Yanwei , Cooper Jason K. , Sharp Ian D. , Bell Alexis T. , Ager Joel W.
Published: May 2015

In this paper, we propose that a p-type transparent conducting oxide (p-TCO) can function as a selective hole contact and corrosion protection layer on photoanodes used for light-driven water oxidation. To prove the concept, NiCo2O4 was used as the p-TCO for n-Si protection in alkaline condition, and we show that this material has the requisite electronic structure, stability, transparency, and hole conductivity to achieve sustained and efficient solar water oxidation. The photoelectrochemical performance demonstrates the attractive combination of transparency and low-resistance hole conductivity in the NiCo2O4. Long-term testing indicates multi-day stability with minimal decrease in performance or observable corrosion of the Si photoanode. This works suggests that p-TCOs are promising as corrosion protection layers for stable water oxidation photoanodes.
Atomic Layer Deposition of i-Sb2S3/p-NiO Thin Layers into Anodic Alumina Membranes for Photoelectrochemical Water Splitting
Authors: Barr Maissa , Assaud Loic , Wu Yanlin , Bachmann Julien , Santinacci Lionel
Published: May 2015

A nanostructured photocathode was fabricated by atomic layer deposition (ALD) of NiO and Sb2S3 in nanoporous alumina. The fabrication, i.e. the successive ALD of NiO and Sb2S3, and the characterization of the arrays of coaxial NiO/Sb2S3 junction by electron microscopies are first reported. The optical and photoelectrochemical preliminary testing of the combination of such extremely thin absorber, Sb2S3, with a p-type semiconductor, NiO, are proposed in a second part. Although the photoconversion performances should be improved, the present work demonstrates validity of the concept.
(Invited) Investigations into the Formation of Germanene Using Electrochemical Atomic Layer Deposition (E-ALD)
Authors: Ledina Maria , Liang Xuehai , Kim Youn-Geun , Jung Jin , Perdue Brian , Tsang Chu , Soriaga Manuel , Stickney John Lewellen
Published: May 2015

This paper will discuss possible formation of germanene electrochemically. Germanene should be a single layer allotrope of Ge. The techniques of in-situ electrochemical STM (EC-STM), voltammetry, coulometry, and micro-Raman have been used to investigate the electrochemical formation of germanene. Studies on Au(111) show that the initial deposition of Ge is kinetically slow and somewhat unstable, whereas the self-limited layer of Ge is stable and shows atomic distances of about 0.44 nm ± 0.02 nm. Micro-Raman was performed on Ge nanofilms, but only displayed a shift near 290 cm-1 in one area. Given the STM results, it appears that the coherence of the germanene domains will need to be increased in order to more consistently produce the Raman signal. The data presented suggest that germanene has been formed electrochemically, although only as a minority species.
ZnO Electrodeposition on Boron-Doped Diamond: Effects of Zinc Precursor Concentration
Authors: Gautier Pierrick , Vallée Anne , Etcheberry Arnaud , Simon Nathalie
Published: May 2015

The cathodic electrodeposition of zinc oxide has been widely studied on various substrates in the last decades. The boron doped diamond (BDD) is a non conventional wide band gap semiconductor, which offers new possibilities as a substrate for this electrochemical deposition. Thus, in the present work, we study the deposition process performed with zinc chloride and dissolved oxygen as a precursor. The effect of zinc precursor concentration in a range of 0.2 to 5 mM is tested at 60°C. The current transient curves coupled with X-Ray Diffraction and Scanning Electron Microscopy analysis, reveal the effect of this parameter on the morphology of obtained ZnO/BDD deposits. Interestingly, the formation of ZnO pyramids was highlighted for the first time.
Cleaning Solution Effect on Electrical and Reliability Properties of Dense and Porous Low Dielectric Constant Materials
Authors: Cheng Yi-Lung , Huang Chi-Jia
Published: May 2015

The effects of different cleaning solutions and various immersion times on the physical, electrical, and reliability characteristics of dense and porous low-k dielectric films were investigated in this study. After immersing into a wet cleaning solution, both low-k dielectric films are needed to remove the physically-adsorbed water by a post-baking process in order to ensure a better performance. The experimental results indicated that irrespective of acid HF and basic NH4OH solutions, they would cause negative impacts on the low-k films, even performing a post-baking process due to the existence of chemically-bonded moisture. The formation of chemically-adsorbed moisture was serious for the porous low-k dielectric films in the NH4OH solution. In addition to the adsorbed moisture, the HF solution caused the low-k dielectric's structure and porosity to be modified and its impact increased with the immersion time. Except the positive benefit in reducing the dielectric constant, these changes caused the degradation in electrical and reliability performance for low-k dielectric films.
Surface Metal Cleaning of GaN Surface Based on Redox Potential of Cleaning Solution
Authors: Nagao Kenji , Nakamura Kenichi , Teramoto Akinobu , Shirai Yasuyuki , Imaizumi Fuminobu , Suwa Tomoyuki , Sugawa Shigetoshi , Ohmi Tadahiro
Published: May 2015

The efficacy of wet cleaning on GaN surface to remove the metal contamination, such as Fe, Ni, Cu, and Zn, has been investigated using total-reflection X-ray fluorescence analyzer (TXRF). Metal contamination on GaN surface can be reduced by the solutions with low pH and high redox potential. The start redox potential of the metal oxidation on GaN surface is larger than that of metal itself. Because metal can receive electrons from GaN surface, and then metal cannot be oxidized to ionization by solutions. The metal contamination on GaN can be reduced by the solutions with the pH less than 4.2 and the redox potential larger than 0.8 V are required. In addition, the cleaning solution required the etching ability of β-Ga2O3, because some kind of metals include in the native oxide of GaN, which is like β-Ga2O3. This method is very useful for metal cleaning and very effective for reducing chemical consumption.
Annealing Effects on the Electrical Activation of Si Dopants in InGaAs
Authors: Lind Aaron Gregg , Aldridge Henry Lee , Bomberger Cory Carl , Hatem Chris , Zide Joshua M. O. , Jones Kevin Scott
Published: May 2015

The thermal stability of Si dopants incorporated during growth and via ion implantation was investigated as a function of annealing time and temperature. Ion implanted samples show a maximum achievable doping concentration of 1.4×1019 cm-3. Growth doped samples exhibit higher post growth electrical activations than achievable in ion implanted samples but subsequent thermal processing at 750°C for 10 minutes is shown to deactivate heavily doped (3×1019 cm-3) MBE doped substrates to the same active doping concentration of 1.4×1019 cm-3 suggesting a common thermodynamic limit to Si activation in InGaAs.
Electrochemical Transfer Doping: A Novel Phenomenon Seen in Diamond, Gallium Nitride, and Carbon Nanotubes
Authors: Chakrapani Vidhya
Published: May 2015

The oxygen redox couple in adsorbed water films acts as an “electrochemical ground” that tends to pin the Fermi level in solids at the electrochemical potential of the redox couple. This paper discusses this effect on the conductivity of diamond; the conductivity type of sp2-based carbons including single-walled, semiconducting carbon nanotubes; the photoluminescence of GaN.
(Invited) Growth of Non-Polar Cubic GaN on Common Si
Authors: Durniak Mark , Bross Adam , Elsaesser David , Chaudhuri Anabil , Lee S C , Brueck Steven R.J. , Wetzel Christian
Published: May 2015

By some accounts group-III nitride may be the widest disseminated man-made compound semiconductors. Yet, what is it that makes it so successful? Maybe the wurtzite structure which allows for piezoelectric polarization? We know about the Stokes shift it induces and its associated troubles. So we rush to reduce polarization in non-polar growth. But how about the cubic form of GaN. Shouldn't that be free of polarization? Would it be the better light emitter even? To find out we prepare GaN and GaInN/GaN heterostructures in cubic lattice form. By virtue of some patterning we achieve cubic growth on the more common form of Si, the (001) orientation, which further allows for conceptional integration with the semiconductor of industry choice.
The Effect of Interfacial Contamination on Antiphase Domain Boundary Formation in GaAs on Si(100)
Authors: Barrett Caleb Shuan Chia , Lind Aaron Gregg , Bao Xinyu , Ye Zhiyuan , Ban Keun-Yong , Martin Patrick , Sanchez Errol , Jones Kevin Scott
Published: May 2015

The suppression of defects such as antiphase domain boundaries (APBs) is a key challenge in the effort to integrate III-V compound semiconductor devices on Si. The formation of APBs naturally arises from growing a polar material on a nonpolar substrate. Surface contamination present on the substrate prior to growth can also disrupt the ordering of atoms in an epitaxial layer and lead to extended defects. In this study, the amount of contamination on Si(100) wafers was varied by approximately an order of magnitude to investigate the effect on formation of APBs in an epitaxial GaAs film grown by MOCVD. The results indicate a direct correlation between the interfacial oxygen and carbon impurity dose and the APB density.
Atomic Level Simulation of Ridge Reconstruction and Passivation in GaAs Nanopillars
Authors: Yu Ted H. , Ratsch Christian
Published: May 2015

Semiconductor nanopillars have unique geometries that make them very promising photo-voltaic materials. In order to improve their performance, we need to understand the role of stacking faults and chemical passivation. It is experimentally observed that most GaAs nanopillars exhibit polytypism that includes Zn blende (ABC) and wurtzite (AB) stacking. We use density-functional theory to compare the simplest four-layered polytype stackings, that contain 50% of each stacking. We calculate their band gap and determine the energy for ridge reconstruction. We also discuss how sulfur passivation leads to the removal of midgap states, and thus improves the solar cell conversion efficiency.
(Invited) Fabrication and Applications of High-Efficiency, Lightweight, Multi-Junction Solar Cells by Epitaxial Liftoff
Authors: Elarde Victor Christopher , Miyamoto Haruki , Chan Ray , Stender Chris , Youtsey Chris , Adams Jessica G J , Wibowo Andree , Tatavarti Rao , Osowski Mark , Pan Noren
Published: May 2015

MicroLink Devices has developed an epitaxial liftoff (ELO) technology for removing thin device layers from the surface of a semiconductor wafer using a flexible metallic sheet to provide structural support. The wafer is left intact and available for use in a subsequent growth cycle. This technology has been applied to high-efficiency, multi-junction solar cells. Removal of the substrate allows the devices to achieve very high specific power of approximately 1000W/kg. For large area devices, the cost of the substrate can be a significant component of the overall device manufacturing cost. By utilizing ELO technology to reuse the substrate for multiple growth cycles, the manufacturing cost of the device can be dramatically reduced.
(Invited) Dilute-Nitride-Antimonide Materials Grown by MOVPE for Multi-Junction Solar Cell Application
Authors: Mawst Luke J , Kim T. W. , Kim H. , Kim Y. , Kim K. , Lee J. J. , Kuech Thomas F , Lingley Z. R. , LaLumondiere S. D. , Sin Y. , Lotshaw W. T. , Moss S. C.
Published: May 2015

We have investigated the growth by metalorganic vapor phase epitaxy (MOVPE) of multinary (four- and five- element) dilute-nitride-antimonide materials on GaAs substrates. The lowest background carbon concentration (~ 5 × 1016 cm-3) is observed in dilute-nitride materials grown at high temperature which do not contain Sb (i.e. InGaAsN). An increased depletion region width significantly improves the solar cell performance over that found from dilute-nitride cells grown at lower growth temperatures (~525oC). The device performance of the single-junction solar cells with the low carbon background InGaAsN base region (InGaAsN/Ge double-junction solar cell) exhibit short-circuit current density, open-circuit voltage, fill factor, and efficiency values of 26.05 (28.46) mA/cm2, 0.67 (0.9) V, 75.85 (72.8) %, and 13.2 (18.54) %, with anti-reflecting coating (ARC), respectively.
(Invited) InAs/InAs1-XSbx Type-II Superlattices for High-Performance Long-Wavelength Infrared Medical Thermography
Authors: Razeghi Manijeh , Haddadi Abbas , Chen Guanxi , Chevallier Romain , Hoang Ahn Minh
Published: May 2015

We present the demonstration of a high-performance long-wavelength infrared nBn photodetectors based on InAs/InAs1-xSbx type-II superlattices on GaSb substrate. The photodetector’s 50% cut-off wavelength was ~10 mm at 77K. The photodetector with a 6 mm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 mm, corresponding to a quantum efficiency of 54% at -90 mV applied bias voltage under front-side illumination and without any anti-reflection coating. With an R×A of 119 Ω·cm2 and a dark current density of 4.4×10-4 A/cm2 under -90 mV applied bias voltage at 77 K, the photodetector exhibited a specific detectivity of 2.8×1011 cm./W. This photodetector opens a new horizon for making infrared imagers with higher sensitivity for medical thermography.
Template-directed Synthesis of Ag2S-Fe2O3 Heterostructures
Authors: Chen Yingjie , Liu Shiben , Zhao Mei , Yu Liyan , Dong Hongzhou , Dong Lifeng
Published: May 2015

Controlled synthesis of optical-magnetic nanostructures has attracted more and more interest due to their enhanced performance for simultaneous optical applications and magnetic manipulating. Herein, we demonstrated the synthesis of nanocomposites containing silver sulfide and iron oxide materials by the sulfidation of silver-iron oxide nano-templates with elemental sulfur as sulfur resource. In the presence of oleylamine, the sulfidation of silver-iron oxide core-shell nanoparticles followed a “coalescence-fracture-ripening” process just like the reported sulfidation of silver nanoparticles. Meanwhile, while the sulfidation products of silver-iron oxide heteromers retained similar nanostructures as templates, indicating an in-situ sulfidation of silver. These investigations will help us to understand the sulfidation and growth process of silver-containing nanomaterials and control their syntheses for potential applications.
(Invited) The Stability of High Voltage AlGaN/GaN HEMTs
Authors: Huang Chih-Fang , Chang Ting-Fu , Wang Yun-Hsiang , Liang Yung C.
Published: May 2015

In this study we investigated the effects of gate stress and body stress on the stability of high voltage AlGaN/GaN HEMTs, emphasizing on the variation of threshold voltage under different stress conditions. Devices with a Schottky gate, a recess MIS gate, and a p-GaN gate design were tested. Gate stresses were imposed with different pulse conditions. Body stresses were performed with a constant voltage or a constant current applied at the body electrode. The experiment results show that Schottky gate devices have a smaller threshold voltage variation and hence are more robust under all these stress conditions.
(Invited) Plasmonic Terahertz Detectors
Authors: Shur Michael
Published: May 2015

We review the achieved and potential performance of plasmonic terahertz detectors implemented in III-N, III-V, and Si materials systems and operating in the overdamped and resonant regimes. Such detectors have been using single transistors and transistor arrays. They operated in a wide temperature range – from cryogenic to elevated temperatures – and in the frequency range from 0.2 THz to 5 THz with Noise Equivalent Powers as low as 1 pW/Hz1/2. The predicted modulation frequencies reach into the THz range. Each materials system (III-N, III-V, and Si) has its optimum frequency range of operation. High mobility InGaAs plasmonic HEMT detectors are expected to operate efficiently up to 10 THz and higher. For the III-N plasmonic transistors, the operation range could reach or exceed 1 or 2 THz. Si CMOS could work as efficient plasmonic THz detectors up to 1 THz or higher. The optimum channel length for each frequency range depends on the materials system. The detection of single THz pules with plasmonic detectors has also been achieved. These THz detectors are expected to find numerous applications in sensing, imaging, wireless communications, and security systems.
Detection of HIV-1 RT Protein Using AlGaN/GaN High Electron Mobility Transistors
Authors: Chu Chia-Ho , Hsu Chen-Pin , Wang Yu-Lin
Published: May 2015

As AIDS caused by (human immunodeficiency virus type 1) has now spread to every country in the world. Statistics show that approximately 40 million people are currently living with HIV infection, and an estimated 35 million have died from this disease since the beginning of the epidemic1. In this study, we use DNA-immobilized AlGaN/GaN high electron mobility transistors (HEMTs) for detecting low concentration of HIV-1 RT protein (1 fM) binding with duplex DNA (dsDNA) electronically, showing that the technique is promising for biosensor applications.
The Photoluminescence Properties of CuInS2 and AgInS2 Nanocrystals Synthesized in Aqueous Solutions
Authors: Borkovska L. , Romanyuk A , Strelchuk V. , Polishchuk Yu. , Kladko V. , Stroyuk O. , Raevskaya A. , Kryshtab T.
Published: May 2015

The results of investigations of the AgInS2 and CuInS2 nanocrystals (NCs) by the photoluminescence (PL), PL excitation (PLE), optical absorption, Raman scattering and X-ray diffraction (XRD) methods are presented. The NCs were synthesized under stoichiometric conditions in aqueous solutions in the presence of aliphatic mercapoacids and transferred in polymer films of gelatin. The XRD patterns and Raman spectra indicated formation of the AgInS2 and CuInS2 NCs of chalcopyrite phase mainly of the average size of about 4 and 2 nm, respectively. The PL spectra of the NCs showed intense defect-related band being much broader for the AgInS2 crystallites. The PLE spectra demonstrated strong dependence on the emission position in the PL spectrum. The low-temperature PL study showed that the PL band of the AgInS2 NCs consisted of two components originated from the ensembles of the NCs of different crystal structure presumably of the chalcopyrite and cubic phases.
Metallization Reliability and Defectivity in Compound Semiconductors
Authors: Kilgore Steve
Published: May 2015

Compound semiconductor devices are in mass volume production, yet our understanding of reliability and defectivity of III-V materials is still evolving. Process-induced defects in electroplated Au interconnect metallization on GaAs devices were detected during the course of reliability testing. Abnormally high lognormal sigmas (σ > 0.7) indicated the existence of a bi-modal failure mechanism. A distinct early lifetime failure mode was observed along with the intrinsic electromigration metallization wear-out failure mode. Failure analysis of an early Au structure failure showed an unusually large void at the atypical anode end. Physical characterization of the electroplated Au film revealed as-deposited nanoscale voids. Elimination of these voids through process improvement as well as proposed mechanisms for the early Au failures are discussed.
5-HT1Areceptors of the nucleus tractus solitarii facilitate sympathetic recovery following hypotensive hemorrhage in rats
Authors: Vantrease Jaime E. , Dudek Nichole , DonCarlos Lydia L. , Scrogin Karie E.
Published: May 2015

The role of serotonin in the hemodynamic response to blood loss remains controversial. Caudal raphe serotonin neurons are activated during hypotensive hemorrhage, and their destruction attenuates sympathetic increases following blood loss in unanesthetized rats. Caudal raphe neurons provide serotonin-positive projections to the nucleus tractus solitarii (NTS), and disruption of serotonin-positive nerve terminals in the NTS attenuates sympathetic recovery following hemorrhage. Administration of 5-HT1A-receptor agonists following hemorrhage augments sympathetic-mediated increases in venous tone and tissue hypoxia. These findings led us to hypothesize that severe blood loss promotes activation of 5-HT1Areceptors in the NTS, which facilitates sympathetic recovery and peripheral tissue perfusion. Here, we developed an adeno-associated viral vector encoding an efficacious small hairpin RNA sequence targeting the rat 5-HT1Areceptor. Unanesthetized rats subjected to NTS injection of the anti-rat 5-HT1Asmall hairpin RNA-encoding vector 4 wk prior showed normal blood pressure recovery, but an attenuated recovery of renal sympathetic nerve activity (−6.4 ± 12.9 vs. 42.6 ± 15.6% baseline, P < 0.05) 50 min after 21% estimated blood volume withdrawal. The same rats developed increased tissue hypoxia after hemorrhage, as indicated by prolonged elevations in lactate (2.77 ± 0.5 vs. 1.34 ± 0.2 mmol/l, 60 min after start of hemorrhage, P < 0.05). 5-HT1AmRNA levels in the commissural NTS were directly correlated with renal sympathetic nerve activity ( P < 0.01) and inversely correlated with lactate ( P < 0.05) 60 min after start of hemorrhage. The data suggest that 5-HT1Areceptors in the commissural NTS facilitate tissue perfusion after blood loss likely by increasing sympathetic-mediated venous return.
Metamaterial Inspired Microstrip Antenna Investigations Using Metascreens
Authors: Tauseef Asim Muhammad , Ahmed Mushtaq
Published: May 2015

A dual layer periodically patterned metamaterial inspired antenna on a low cost FR4 substrate is designed, simulated, fabricated, and tested. The eigenmode dispersion simulations are performed indicating the left handed metamaterial characteristics and are tunable with substrate permittivity. The same metamaterial unit cell structure is utilized to fabricate a metascreen. This metascreen is applied below the proposed metamaterial antenna and next used as superstrate above a simple patch to study the effects on impedance bandwidth, gain, and radiation patterns. The experimental results of these antennas are very good and closely match with the simulations. More importantly, the resonance for the proposed metamaterial antenna with metascreen occurs at the left handed (LH) eigenfrequency of the metamaterial unit cell structure. The measured −10 dB bandwidths are 14.56% and 22.86% for the metamaterial antenna with single and double metascreens, respectively. The metascreens over the simple patch show adjacent dual band response. The first and second bands have measured −10 dB bandwidths of 9.6% and 16.66%. The simulated peak gain and radiation efficiency are 1.83 dBi and 74%, respectively. The radiation patterns are also very good and could be useful in the UWB wireless applications.
Design of a Smart Antenna for Mobile Ad Hoc Network Applications
Authors: Di Filippo Marco , Lucci Leonardo , Marabissi Dania , Selleri Stefano
Published: May 2015

Among the mobile ad hoc networks appealing characteristics there are network reconfigurability and flexibility. In this context a smart antenna capable of self-configuring multiple high-directivity beams provides a major advantage in terms of power saving, increased range, and spatial reuse of channels. In this paper a smart antenna made of a cylindrical array of patches suitable for MANETs is presented.
High-Efficiency Electromagnetic Wave Controlling with All-Dielectric Huygens’ Metasurfaces
Authors: Wang Zheng-bin , Shi Jin , Chen Jin-chang
Published: May 2015

Subwavelength dielectric blocks with varying thicknesses are introduced to realize 0∼2πphase change. A Huygens’ metasurface composed of such nonuniform building blocks is shown to efficiently refract normally incident waves in a broadband. According to the same physical mechanism, we fabricate an electrically thin lens with concentric subwavelength dielectric blocks and integrate it with a patch antenna to form a three-dimensional (3D) ultra-low-profile lens antenna system. Full-wave simulation demonstrates the lens antenna’s excellent performances in high directivity, broadband, low loss, and low side-lobe levels.
Suture Distension of Schlemm’s Canal in Canaloplasty: An Anterior Segment Imaging Study
Authors: Brandao Livia M. , Schötzau Andreas , Grieshaber Matthias C.
Published: May 2015

Purpose. The object of this study was to investigate the role of the suture stent regarding its impact on reduction of intraocular pressure (IOP) in canaloplasty based on the distension of the inner wall of Schlemm’s canal.Methods. Nineteen glaucoma patients who underwent canaloplasty with successful positioning of the tensioning suture were included. The measurements were analyzed using linear mixed models, with the means adjusted to IOP, age, cup-to-disc ratio, and time of follow-up.Results. Mean follow-up time was 27.6 months (SD 10.5). Mean intraocular pressure (IOP) was 24.6 mmHg (SD 5.29), 13.8 (SD 2.65), and 14.5 (SD 0.71) before surgery, at 12 months, and at 36 months after surgery, respectively. 57.9% of patients had no medication at last evaluation. Differences and variations of measurements between the devices over a time of 12 months were not significant (p= 0.15 to 0.98). Some angles of distension associated with the suture stent inside SC were predictive for IOP reduction (p< 0.03 to < 0.001), but not for final IOP (p= 0.64 to 0.96).Conclusion. The angles of the inner wall of Schlemm’s canal generated by the suture stent were comparable between OCT and UBM and did not change significantly over time. There was a tendency towards a greater distension of Schlemm’s canal, when the difference was larger between pre- and postoperative IOP, suggesting the tensioning suture may contribute to IOP reduction.