bluuebunny/crossref_metadata_2025 huggingface dataset:
Room-Temperature Bonding of Oxide Wafers by Ar-beam Surface Activation
Authors: Takagi Hideki , Utsumi Jun , Takahashi Masaharu , Maeda Ryutaro
Published: October 2008

Surface activated bonding (SAB) by Ar beam sputter etching has been proved to have ability to bond various semiconductor wafers at room temperature. In this paper, we report SAB of oxide wafers. Various oxide wafers were successfully bonded to Si wafers by SAB. Strong bonding equivalent to bulk strength was achieved without any heat treatments. Among the oxide wafers tested, SiO2 was only a material which was not form strong bond with Si at room-temperature. On the other hand, strength of oxide-to-oxide bonding by SAB was not so strong as bulk materials and was largely dependent on the bonded oxide materials. In case of oxide-to-oxide bonding, SiO2 was again difficult to bond. Deposited thin oxide film such as TiO2 could be bonded by SAB and was effective to improve bonding properties. In summary, oxide wafers were successfully bonded by SAB at room-temperature, however its strength depends on oxide materials.
Plasma Activation for Low Temperature Wafer Bonding
Authors: Plach Thomas , Dragoi Viorel , Murauer Franz , Hingerl Kurt
Published: October 2008

Wafer bonding behavior of plasma activated Si and SiO2 surfaces was investigated. Process evaluation was performed by various experiments. Surface energy of wafer pairs bonded after different storage times at room temperature and after thermal annealing at 300oC was investigated as a measure of surface activation lifetime. Plasma activation was studied also for room temperature storage of pre-bonded pairs, as well as for low temperature annealing (50{degree sign}C) of the bonded pairs. The effect of the plasma treatment on the surface microroughness was studied. The quality of the bonded interfaces was explored by TEM cross section analysis.
Laser Transmission Bonding of Silicon-to-Silicon and Silicon-to-Glass for Wafer Level Packaging and Microsystems
Authors: Sari Fahri , Wiemer Maik , Bernasch Michael , Bagdahn Joerg
Published: October 2008

Miniaturization in the semiconductor industry and in microsystems shows that the packaging of sensitive chips with multiple functions is becoming more and more important regarding mechanical stress induced by temperature change during the conventional bonding process. Laser Transmission Bonding (LTB) with selective heat input allows a small heat-affected zone (HAZ) along the bonding frames. The chips can thus be joined without any temperature load in the functional area on Wafer Level or Chip-Level. This paper will present first bonding results determining the joinability of silicon-to-silicon samples by applying a cw-thulium fiber laser at wavelength of 1908 nm using an absorbing intermediate layer at the interface. Furthermore, a part of a study will briefly present results evaluating the mechanical strength (burst pressure) of silicon-glass bonds by applying a cw-Nd:YAG-laser at wavelength of 1064 nm.
Growth, Fabrication, and Characterization of High-Speed 1550-nm S-SEEDs for All-Optical Logic
Authors: Keeler G. A. , Serkland D. K. , Overberg M. , Klem J. F. , Geib K. M. , Clevenger J. B. , Hsu A. Y. , Hadley G. R.
Published: October 2008

We describe recent advances in the development of 1550-nm symmetric self-electrooptic effect devices (S-SEEDs). S-SEEDs are semiconductor optoelectronic devices used to implement ultrafast all-optical logic functions for optical fiber communication applications. In this paper, basic S-SEED operation is described, followed by a detailed explanation of the optimization techniques used to improve DC and high-speed performance in these long wavelength devices. Both epitaxial strain and quantum well design are shown to be important for S-SEEDs grown in the InAlGaAs quaternary material system. The device fabrication approach is outlined, and DC electrical and optical performance is discussed. Finally, we describe the high-speed optoelectronic measurements used to determine S-SEED switching characteristics. The devices described herein are the first known S-SEEDs to operate at telecommunications-compatible wavelengths and demonstrate record switching speeds with rail-to-rail switching rates faster than 6 picoseconds.
High Density Copper Bump Technology Integrated With Wafer Level Package
Authors: Zeng Xiang , Chang-Chien Patty , Cheung Chi , Akerling G , Johnson Rosie , Chung T. , Hennig Kelly
Published: October 2008

Sub-100um fine pitched copper pillars are fabricated using standard semiconductor wafer batch processing techniques. As traditional solder bumps reach their resolution limits, this technology offers performance improvements and compliments advances in flip chip and wafer level packaging technology. A 2-wafer level bonded Ku-Band phase shifter MMIC wafer stack is integrated to PCB assembly with copper pillar interconnects between chip and board, and a fully functional 3-bit phase shifter module has been demonstrated
Directed Crystallization under Nanoscopic Cylindrical Confinement
Authors: Lee Jaesung , Noh Kyong , Woo Euntaek , Huh June , Jeong Young , Kim Kwang-Woo , Shin Kyusoon
Published: October 2008

The crystal orientation of one-dimensional Bi nanorods under nanoscopic cylindrical confinement is investigated. XRD confirmed the alteration of crystal orientation after recrystallization, and we observe changes of thermal properties in DSC thermograms. The melting of the nanorods occurs at lower and broader temperature ranges than that of bulk. The studies about homogeneous and heterogeneous crystallization enlighten these observations and provide characteristic feature of crystallization under nanoscopic cylindrical confinement.
Analysis of Intrinsic and Parasitic Gate Delay of InGaAs HEMTs
Authors: Suemitsu Tetsuya
Published: October 2008

In this paper, the principles, measurement techniques, and analysis of the gate delay of high-electron-mobility-transistors (HEMTs) mainly based on an InP material system are discussed. In the measurement techniques, de-embedding of the pad parasitics is also described. The intrinsic part of the gate delay of HEMTs is the transit time for electrons to travel in the gate depletion region. When the gate length is large enough, the intrinsic gate delay is dominant in the total gate delay. However, as the gate length becomes less than 100 nm, the delay analysis reveals that the intrinsic gate delay is now no longer dominant but the parasitic gate delay ascribed to the resistance and capacitance out of the gate region. Based on these results, ways for further improvement of the frequency response are also discussed.
An Efficient Self-Driven CM-n-TiO2 / p-GaInP2 Photoelectrochemical Cell for Water Splitting
Authors: Ingler William B. , Shaban Yasser A. , Khan Shahed U.
Published: October 2008

A self-driven carbon modified CM-n-TiO2 / p-GaInP2 photoelectrochemical cell (PEC) was found to split water under illumination intensity of 200 mW cm-2 from a solar simulator with a global AM 1.5 filter. This photoelectrochemical cell shows a photocurrent density of of 16.33 mA cm-2 and evolution of 2.78 μL of H2 gas s-1cm-2 of photoelectrode area at zero bias. The PEC was found to split water directly upon illumination without the need of using bias potential from any external source. The water splitting efficiency of this self-driven PEC was found to be 13.3 % for hydrogen gas production under solar simulated light illumination with a global AM 1.5 filter (1 sun).
Effect of the Silver Mirror Location on the Luminance Intensity of Double Roughened GaN Light-Emitting Diodes
Authors: Huang Ping Wei , Wu YewChung Sermon
Published: October 2008

Four kinds of mirror systems were used to investigate the effect of the Ni thin film on the reflectivity of GaN light-emitting diodes after annealing at 200° for 1 h. Samples designated as "ITO/Ag " were ITO/Ag films without Ni layer. "ITO/Ni/Ag " and "ITO/Ag/Ni " were ITO/Ag films with a Ni layer either between the ITO and Ag films, or on the backside of Ag film. "ITO/Ni/Ag/Ni " were ITO/Ag films with Ni layers on both sides of Ag film. It was found that annealed-ITO/Ni/Ag/Ni had the highest reflectivity (96.3%). The thin Ni film could served as a diffusion barrier to retard the in-diffusion of Ag into ITO and the agglomeration of Ag. Therefore annealed-ITO/Ni/Ag/Ni had the highest reflectivity.
Thermal Management Design from Chip to Package for High Power InGaN/sapphire LEDs Applications
Authors: Horng Ray-Hua , Chiang Cheng-Chung , Wuu Dong-Sing , Lin Heng-I , Tsai Yu-Li
Published: October 2008

The optical and thermal properties of blue InGaN/sapphire LEDs with a novel structure design for heat dissipation is investigated. The LED chip is designed to directly contact with a cup-shaped Cu heat spreader, and then mounted on a heat sink coated with a diamond-like film. The packaged LED chip with the novel heat dissipation design demonstrates superior light output power and reduced junction temperature as compared with the same LED chip packaged using conventional process.
Light Output Power Enhancement of GaN-based Vertical Light Emitting Diodes via Fabricating Surface Nanorod Arrays
Authors: Chiu ChingHua , Kuo H. C. , Lu T.C. , Wang S.C. , Hsiao C.S. , Chen S.Y.
Published: October 2008

In this research, we demonstrated two approaches to fabricate nanorod arrays on the surface of GaN-based vertical light emitting diodes (VLEDs). The first approach was via synthesizing single-crystal ZnO nanorod arrays in aqueous solution at room temperature. The light output intensity and wall-plug efficiency of the GaN-based VLEDs with the ZnO nanorod arrays shows 38.9 and 41.2% increases, respectively, at 200 mA current injections compared to that of a VLED without ZnO nanorod arrays. The second approach was formed by spinning nano silica spheres and inductively coupled plasma-reactive ion etching. The light output power of the VLEDs with the dry etched nanorod arrays showed about 40% enhancement than that without the nanorod arrays. The large enhancement of VLED with both ZnO or GaN nanorod arrays was mainly due to the total internal reflection destruction, and the gradually changed refractive index from the nanorod arrays layer.
Wireless Hydrogen Sensor Networks Using AlGaN/GaN High Electron Mobility Transistor Based Differential Diodes Sensor
Authors: Yu X , Li C , Low Z , Lin J , Anderson T J. , Wang H T. , Ren F. , Wang Y L. , Chang C Y. , Pearton Stephen J. , Hsu Chien-Hsing , Osinsky A , Dabiran Amir M. , Chow P , Balaban C , Painter J
Published: October 2008

We have demonstrated a wireless hydrogen sensing system using commercially available wireless components and AlGaN/GaN High Electron Mobility Transistor (HEMTs) differential sensing diodes as the sensing devices. The active device in the differential pair is coated with 10 nm of Pt to enhance catalytic dissociation of molecular hydrogen, while the reference diode is coated with Ti/Au. Our sensors have a wide range of detection from ppm levels to ~30%, with the added advantages of a very rapid response time within a couple of seconds, and rapid recovery. The sensors have shown good stability for more than 18 months in an outdoor field test.
InGaN-based Light Emitting Diodes with Photoelectrochemical Lateral Etching Process on InGaN Active Layers
Authors: Lin Chia-Feng , Yang Chung-Chieh , Liu Hsun-Chih , Lin Chun-Min , Chen Kuei-Ting , Chien Jui-Fen
Published: October 2008

The InGaN-based Light Emitting Diodes (LEDs) with a wider lateral etched InGaN active layer were fabricated through the photoelectrochemical (PEC) etching process with an 800W illuminated Hg lamp, an unintentionally doped GaN filter, and immersed in a 2.2 M potassium hydroxide (KOH) solution. The lateral etched LED structures were achieved by using a GaN filter and InGaN as a sacrificial layer with a 2.57μm lateral etching width. The electroluminescence (EL) wavelengths of InGaN/GaN multi-quantum-well (MQW) active layer were observed at 460nm for standard LED and 455.7 nm for lateral etching LED with 20mA DC injection current. The peak EL emission wavelength had 4.3 nm-blueshift phenomenon in the lateral etched LED compared to standard one that was caused by partial reducing the compress strain in InGaN/GaN active layers. The light output power of the lateral etched LED had 54% enhancement compared to the standard LED. By using the PEC lateral etching process, the selective lateral etched LED structure have higher light scattering process and higher carrier recombination efficiency with lower piezoelectric field for higher efficiency optical device application
11.9 W Output Power at S-band from 1 mm AlGaN/GaN HEMTs
Authors: Krämer Mark , Karouta Fouad , Kwaspen J J. , Rudzinski Marius , Larsen Poul K. , Suiker Erwin M. , De Hek Peter A. , Rödle Thomas , Volokhine Iouri , Kaufmann Leon M.
Published: October 2008

We present radio-frequency (RF) power results of GaN-based high electron mobility transistors (HEMTs) with total gate widths (Wg) up to 1 mm. The AlGaN/GaN epi-structures are MOVPE-grown on 2-inches semi-insulating (s.i.) 4H-silicon carbide substrates. The HEMTs have been fabricated using an optimized process flow comprising a low-power Ar-based plasma after ohmic contact metallization, cleaning of the AlGaN surface prior to the Schottky gate metallization using a diluted ammonia (NH4OH) solution, and passivation of the AlGaN surface using a silicon nitride layer deposited by plasma enhanced chemical vapor deposition. We will show that the best RF power performance has been achieved by HEMTs with iron-doped GaN buffer layers (GaN:Fe). Devices with a total gate width of 1 mm yielded a maximum output power of 11.9 W at S-band (2 - 4 GHz) under class AB bias conditions (VDS = 40 - 60 V, and VGS = -4.65 - - 4.0 V).
Epitaxial Deposition of SiC onto 4H SiC using a Hollow Cathode
Authors: Soukup Rodney J. , Ianno Natale , Huguenin-Love James , Lauer Noel , Hofmann Tino , Hubicka Zdenek
Published: October 2008

Thin films of SiC were deposited using DC, RF and pulsed sputtering of a hollow cathode. The majority of the films were deposited using RF sputtering at temperatures ranging from 610 to 858 degrees C. Initial films were deposited onto Si substrates in order to determine deposition rates, film uniformity, and film composition. The introduction of a rotating substrate holder greatly improved the film thickness and composition uniformity. The samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, optical absorption, and infrared ellipsometry. The initial films were polycrystalline in nature independent of the substrate used for deposition. The 4H/3C polytype ratio increases strongly for elevated substrate temperatures for the films which were grown homo-epitaxially on 4H SiC. This observation suggests a new avenue for homo-epitaxial growth of SiC onto 4H SiC and rapid hollow cathode sputtering is envisioned for the growth of single crystal films of 4H SiC for future device applications.
Polarity Inverted GaN for Photonic Crystal Biosensor Applications
Authors: Tompkins Randy P. , Dawson Jeremy , Hornak Lawrence , Myers Thomas
Published: October 2008

Periodic poling of GaN (alteration of the crystallographic direction along the c-axis) has potential for applications in photonics, sensing, and non-linear optics. One approach to periodic poling of GaN, involves Molecular Beam Epitaxy (MBE) growth of heavily Mg doped GaN which results in inversion of the surface polarity from Ga-polar to N-polar GaN. Fabrication and dry etching of the inversion layer followed by re-growth, and a subsequent highly anisotropic wet etch of re-grown N-polar regions can result in periodically poled GaN with features on either the micro or nanoscale. This paper outlines the design of GaN based photonic crystal biosensors based on periodic poling. Initial results of growth, fabrication, and theoretical modeling will be discussed.
Tailoring Electrochemical Capacitor Energy Storage Using Direct Write Dispenser Printing
Authors: Ho Christine C. , Steingart Daniel , Evans James , Wright Paul
Published: October 2008

We present a direct-write, dispenser printing method for additively fabricating solid-state, thick film carbon supercapacitors directly onto any substrate in room temperature, ambient conditions. This proves to be a flexible method for integrating electrochemical energy storage components onto a device and tailoring its performance to a specific application's demands. The capacitors are made using MCMB (mesocarbon microbead) electrode material in a PVDF (polyvinylidene fluoride) gel binder. The gel is able to encapsulate BMIM+BF4- (1-butyl-3-methylimidazolium tetrafluoroborate) ionic liquid electrolyte, and effectively forms solid-state films. From both galvanostatic and electrochemical impedance measurements, printed capacitors exhibited an average capacitance of 0.50 mF/cm2. These tools were also used to evaluate the long-term cycle life of the capacitors, their power and energy density relationship, and compare transport properties.
Micro- and Mesoporous Carbide-Derived Carbon Materials and Polymer Membranes for Supercapacitors
Authors: Janes Alar , Thomberg Thomas , Tonurist Kerli , Kurig Heisi , Laheaar Ann , Lust Enn
Published: October 2008

Several nanoscale fine-tuned micro- and mesoporous carbon powders C(Mo2C) produced by reacting Mo2C with Cl2 at various temperatures were studied and characterized using XRD and Raman spectroscopy methods and compared with low temperature N2 adsorption/desorption measurements data. Supercapacitors based on two ideally polarizable nanoporous carbon electrodes and different mesoporous commercially available separators in acetonitrile (AN) as the solvent for the 1.0 M (C2H5)3CH3NBF4 electrolyte have been completed and tested by cyclic voltammetry and electrochemical impedance methods.
Capacitor Properties of Bundled Single- and Double-Walled Carbon Naotubes and Their Electrochemical Doping Mechanism
Authors: Yamada Yasuhiro , Kimizuka Osamu , Tanaike Osamu , Machida Kenji , Suematsu Shunzo , Tamamitsu Kenji , Saeki Susumu , Yamada Yoshio , Hatori Hiroaki
Published: October 2008

The correlation between capacitance and the structure of carbon nanotubes was studied. The electrochemical behaviors were characteristic by the electrochemical doping mechanism of semiconducting nanotubes which are amphoteric and can be doped by both donors and acceptors. High specific capacitance and rate performance were shown for uncapped single-walled carbon nanotubes having inner micropores with the diameter less than 1 nm.
Effect of Doping Ions on Capacitance Properties of Polypyrrole/Functionalized Single-walled Carbon Nanotubes Composites
Authors: Wang Jie , Xu Youlong , Wang Leigang , Du Xianfeng
Published: October 2008

Polypyrrole/functionalized single-walled carbon nanotubes composites (PPy/F-SWNTs) were electrochemically prepared in dispersive solution of pyrrole (Py) and F-SWNTs with or without doping ions. The effect of in-situ doping ions including Cl-, ClO4-, toluenesulfonate (TOS-) and dodecylbenzenesulfonate (DBS-) on the capacitance performance of the composites was investigated by cyclic voltammetry (CV), galvanostatical charge/discharge and electrochemical impedance spectroscopy (EIS) techniques. Except the pristine composite and the composite doped by DBS-, the others exhibited notable electrochemical capacitance behaviors. Furthermore, the specific capacitance of PPy-Cl/F-SWNTs (polymerization charge was 2 mAh•cm-2) reached 241 Fg-1 at the scanning rate of 10 mVs-1. PPy-TOS/F-SWNTs (polymerization charge 2 mAhcm-2) had greater capacitance and charge/discharge rate than the former did. Even at the scanning rate of 200 mVs-1, its specific capacitance was still up to 172 Fg-1. But with heaver doping ion (TOS-), PPy-TOS/F-SWNTs (polymerization charge 2 mAhcm-2) had a slightly smaller specific capacitance, such as 196 Fg-1 at the scanning rate of 10 mVs-1.
Manganese Oxides/SWNTs Composite Films via Anionic Surfactant-Directed Electrochemical Synthesis
Authors: Xiao Fang , Xu Youlong , Wang Jie
Published: October 2008

In this work, MnO2/SWNTs composite film was electrodeposited by the galvanostatic anodic oxidation. The plating solution was prepared by manganese sulfate directed on SWNTs via sodium dodecyl benzene sulphonate as the anionic surfactant. It was shown by FE-SEM that the diameters of SWNTs obviously increased. It may be that there were coated MnO2 on their surface. The specific capacitance values of 137.5 F g-1 and 78.3 F g-1 were obtained by the cyclic voltammograms experiment, respectively, at the sweep rate of 10 mV s-1 and 2000 mV s-1. And the impedance studies revealed that the Faraday resistance of MnO2/SWNTs film was lower than that of the pure MnO2 film. It attributes to the excellent conductivity of the SWNTs. The resultant MnO2/SWNTs composite film exhibited stable fast-response character as electrode material for electrochemical capacitors.
Birnessite as Possible Candidate for Hybrid Carbon/MnO2 Electrochemical Capacitor
Authors: Athouël Laurence , Moser François , Dugas Romain , Crosnier Olivier , Bélanger Daniel , Brousse Thierry
Published: October 2008

Birnessite form of manganese dioxide has been investigated as possible electrode material for electrochemical supercapacitor applications. It has been shown that this material exhibits partial sodium cations/protons intercalation which provides pseudo-capacitance leading to a stable value of 145 F/g on 1100 cycles. The use of Mg-doped Na-birnessite as positive electrode of a hybrid carbon/MnO2 electrochemical supercapacitor has also shown an interesting capacitance of 0.12 F, stable on 17000 cycles.
Asymmetrical Electrochemical Capacitors Using Heteropoly Acid Electrolytes
Authors: Lian Keryn K. , Li Changming
Published: October 2008

Asymmetrical electrochemical capacitors using heteropoly acid electrolytes and RuO2-graphite electrodes were investigated. The fabricated devices have a working voltage window of 0 to 1.4 V and can be discharged more efficiently than conventional symmetrical capacitors. Heteropoly acids have been shown to be able to both function as electrolyte and to leverage pseudo-capacitance.
An Asymmetrical Supercapacitor Based on CNTs/SnO2 and CNTs/MnO2 Nanocomposites Working at 1.7 V in Aqueous Electrolyte
Authors: Ng Kok Chiang , Zhang Shengwen , Chen George Z.
Published: October 2008

An asymmetrical supercapacitor was fabricated with a CNTs/SnO2 negative electrode and a CNTs/MnO2 positive electrode. It was tested in charge and discharge to 1.7 V in aqueous electrolyte without showing noticeable current resulting from water decomposition. Physicochemical properties of the CNTs/SnO2 and CNTs/MnO2 nanocomposites were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectrometry (EIS). At a current density of 0.25A g-1, the energy density of the hybrid supercapacitor was found to be 20.3 Whkg-1 which is comparable to that obtained from electric double layer supercapacitors using organic electrolytes (17~18Wh kg-1). The asymmetrical supercapacitor also shows exceptional stability over 1000 cycles with the capacity loss being less than 8%.
Graphite/TiO2 Electrochemical Capacitor as a Safe Electric Energy Storage System
Authors: Thapa Arjun K. , Ishihara Tatsumi , Moriyama Nariaki , Kawamura Toshihiko , Nakamura Hiroyoshi , Yoshio Masaki
Published: October 2008

Graphite/TiO2 electrochemical capacitor has been developed as an electric energy storage system with high capacity as well as high energy density. The crystal structure of anatase and rutile structure of TiO2 have investigated with respect to the performance of capacitors. in situ XRD measurements have been also carried out on the both cathode and anode during the charge of capacitor
Performance & Application based on Graphite/Activated Carbon with Titanium Dioxide Electrode for Electrochemical Capacitor
Authors: Park Soo-Gil , Kim Hong-Il , Yang Jeong-Jin , Kim Han-Joo
Published: October 2008

The capacitive properties of activated carbon electrodes with CNT coated titanium oxide composite electrode were investigated in PC containing TEABF4 or LiPF6 by galvanostatic charge/discharge and electrochemical impedance spectroscopy. The composite electrode showed relatively good electrochemical behaviors better than activated carbon electrode. During cycling, the composite electrode presented 275 mF/cm2 of specific capacitance in TEABF4/PC and reduced resistance.
Transparent MnO2-based Electrochemical Capacitor
Authors: Moser François , Athouël Laurence , Crosnier Olivier , Favier Frédéric , Bélanger Daniel , Brousse Thierry
Published: October 2008

In this paper, a new concept for an electrochemical capacitor is presented. This new symmetrical device includes two MnO2 electrodes separated with a gel electrolyte, which makes the whole system transparent and less than 1mm thick. Preliminary results for such device revealed a capacitance of 5mF/cm2 that can be maintained over 200 cycles.
Controlled Interfacial Synthesis of MnO2 and its Application in Aqueous Supercapacitors
Authors: Roberts Alexander J. , Chandra Amreesh , Slade Robert C. T.
Published: October 2008

A controlled interfacial synthesis has been used to obtain ε - MnO2 of varying surface area between 50 and 160 m2 g-1 and pore volumes between 0.3 and 0.4 cm3 g-1. The synthesis conditions have been shown to have a marked effect on pore size distributions. These materials have been cast into composite electrode films. The differences in pore size and surface areas of the films are compared to those of the precursor powders. After assembly in supercapacitor test cells with aqueous neutral electrolyte, Specific capacitances have been assessed through galvanostatic cycling giving initial values as high as 448 F g-1, dropping to 260 F g-1 after 5 cycles but showing no further degradation over 200 cycles.
Photoluminescence of ZnO Nanowires with Eu Diffusion Process
Authors: Chen C. W. , Pan C. J. , Huang P. J. , Chi G. C. , Chang C. Y. , Ren F. , Pearton Stephen J.
Published: October 2008

ZnO nanowires with europium (Eu) diffusion process are studied. The ZnO nanowires were grown by chemical vapor deposition on Si substrate with employing Au as catalyst. The diameter of the resulting nanowires was about 200 nm with the length of about 1 μm. To perform the diffusion process, the ZnO nanowires were placed with an Eu shot in a furnace at 900ºC. Annealing was performed under vacuum for 1 hr. From photoluminescence spectra excited by a He-Cd laser at room temperature, the green luminescence of the ZnO nanowires with Eu diffusion process observed at about 515 nm is attributed to Eu impurity in ZnO nanowires. Thermal annealing of diffusion process could cause the red shift of near-band-edge emission of ZnO nanowires. From microstructural observations by high-resolution transmission electron microscopy, there exists Eu2O3 formed on the surface of ZnO nanowires after Eu diffusion process.
Evolution of Surface Morphology by Wet-Etching of ZnO and GaN with Different Polarity
Authors: Lee Ji-Myon , Kim Jae-Kwan , Jo Young-Je , Han Seung-Cheol , Kim Taek-Seung , Kim Kyoung-Kook
Published: October 2008

The surface morphologies of ZnO and GaN thin film by wet-chemical etching were investigated. While ZnO was readily etched by acidic solutions regardless of its polarity, GaN was hardly etched by acidic solutions, but etched in alkali-based solutions such as KOH, especially for N-face GaN. Furthermore, we will also discuss the micro-structural evolution of hexagonal pyramids on the O-polar (N-polar) surfaces and hexagonal pits on the Zn-polar (Ga-polar) surfaces of ZnO and GaN, respectively.
Electrical Properties of Zn(Mn,Co)O Films Grown by Pulsed Laser Deposition Method
Authors: Kim Jae-Hoon , Song Hooyoung , Kim Eun Kyu , Lee Sejoon , Shon Yoon
Published: October 2008

High quality ZnO films were made by using a pulsed laser deposition (PLD) system. Through a same method magnetic element doped Zn(Mn,Co)O films were grown. An XRD measurement was tried and the result showed a single crystal of wurtzite structure. A capacitance-voltage measurement showed that the ZnMnO has electrical properties of an n-type semiconductor, and carrier concentration is 5 × 1018 cm-3. From a deep level transient spectroscopy (DLTS) measurement, an oxygen vacancy and a Mn-related electron trap in the ZnMnO film were appeared as Ec-0.62 eV and Ec-0.13 eV, respectively. The electrical measurement of the ZnCoO films showed meaningless results because of its high conductance.
Preparation and Properties of Transition Metal Doped ZnO Nanowires
Authors: Matei Elena , Sima Marian , Enculescu Ionut , Enculescu Monica , Neumann Reinhard , Granville Simon , Ansermet Jean-Philippe
Published: October 2008

We employed template replication by electrochemical deposition as the technique to prepare transition metals doped zinc oxide nanowires. Polycarbonate nanoporous membranes obtained by swift heavy ions irradiation and subsequent etching were used as templates. The pores were filled with the desired material by electrochemical deposition from an aqueous bath. The properties of the nanowires were investigated by scanning electron microscopy, energy dispersive X ray analysis and optical spectroscopy. We investigated the effect of preparation condition (i.e. deposition potential, deposition bath composition) on nanostructures properties
High-Operating Current High-Mobility Thin Film Transistors Using Room-Temperature Sputtering GZO/ZnO as the Channel Layer
Authors: Wu Meng Lun , Liu Kuang Chung , Hsiao Shih Hua , Huang JianJang
Published: October 2008

We demonstrate a high performance delta-GZO TFTs by inserting a thin Ga-doped ZnO layer in between two ZnO layers. The GZO layer is deposited by sputter with a Ga-doped ZnO(Ga2O3-0.5wt%) target. The device shows a drain-source current 2mA at VGS=5V and VDS=18V, which is significantly higher than that of the conventional one. The improvement of the current level is associated with an additional channel path and a lower channel resistance due to the insertion of the GZO layer, which supply additional carriers to the channel layer. Also, the threshold voltage of the device becomes smaller, makes the delta-GZO TFTs almost operate in the depletion mode, while the conventional one is operated in the enhancement mode. The result shows our proposed structure has the advantage of controlling threshold voltages.
Reactive Ion Etching of ZnO Using a Cl2/Ar Mixture
Authors: Hsueh Kuang-Po , Hou Ren-Jie , Kuo Cheng-Huang , Tun Chun-Ju
Published: October 2008

This study investigates physical properties of ZnO films after reactive ions etching (RIE) using a Cl2/Ar mixture by varying the gas flow ratio, radio-frequency (rf) plasma power and chamber pressure. Atomic force microscopy (AFM) results and surface topographies are discussed. The etching rate at a Cl2/Ar flow rate of 150/10 sccm, a work pressure of 60 mTorr and an rf power of 300 W is higher than under any other conditions. Additionally, the root-mean-square (rms) roughness of 24.20 nm is the highest at a Cl2/Ar flow rate of 150/10 sccm, a work pressure of 190 mTorr and an rf power of 300 W; it is suitable for roughened transparent contact layer (TCL) in light-emitting diodes (LEDs). Bearing ratio analysis reveals that, under this condition, the nanorods covered 25.41 % of the total surface area and their maximum height was approximately 150.83 nm.
Exploiting the Benefits of Negative Polarization in n-InGaN/p-GaN Single Heterostructure Light Emitting Diode with p-side Down
Authors: Reed Meredith , Shen Paul , Wraback Mike , Syrkin Alexander , Usikov Alexander
Published: October 2008

In this paper we demonstrate the electrical and optical effects of negative polarization charge at the n-InGaN/p-GaN interface on the performance of single heterostructure n-InGaN/p-GaN LEDs with p-side down. This negative polarization charge at the interface leads to a reduced barrier for hole injection from p-GaN to n-InGaN, with a hole accumulation layer forming within the InGaN near the n-InGaN/p-GaN interface. Electrons encounter a significant barrier for injection from the n-InGaN into p-GaN, compounded by the heterobarrier, making p-GaN behave like an effective electron blocking layer. We show that the combination of 2D hole-gas formation on the n-InGaN side of the hetero-interface and enhancement of the electron barrier to transport across this interface may reduce efficiency droop at high current density without the need for an AlGaN electron blocking layer.
Si/SiGe Epitaxy and Selective Etch Applications for Advanced Thin-Films MOSFET Structures
Authors: Loubet Nicolas , Boeuf Frédéric , Monfray Stéphane , Fenouillet-Beranger Claire , Denorme Stéphane , Bidal Grégory , Skotnicki Thomas , Dutartre Didier
Published: October 2008

In this contribution, we are focusing on low temperature Si and SiGe epitaxy for the fabrication of thin-films transistors devices. In particular, we will consider two different approaches: the first one is the use of FDSOI substrates in combination with a poly-selective Si epitaxy. The second one is the use of conventional wafers for the fabrication of SON devices where SiGe can be employed as a sacrificial layer to form very-thin buried ONO below the transistor channel. Some electrical results on FDSOI, folded Bulk+, and localized SOI with TiN/HK gate stack are presented showing a perfect control of the SCE and DIBL with a very low Ioff which is mandatory for advanced CMOS low power applications
Carbon- and Tin- Incorporated Source/Drain Stressors for CMOS Transistors
Authors: Yeo Yee-Chia
Published: October 2008

We explore several technology options for forming lattice-mismatched source/drain (S/D) stressors for enhancing the performance of complementary metal-oxide-semiconductor (CMOS) field-effect transistors. Recent research on silicon-carbon [Si:C or Si(1-y)C(y)] S/D stressors for n-FETs will be reviewed. Device integration work involving epitaxial Si:C S/D with high carbon concentration and in situ doping, as well as alternative technologies for forming Si:C S/D, e.g. using implantation and anneal, will be discussed. For p-FETs, tin-incorporated S/D stressors will be explored. Integration of new stressors in advanced device architectures is expected to enable the realization of ultimate CMOS performance.
Performance Evaluation of 15nm Gate Length Double-Gate n-MOSFETs with High Mobility Channels: III-V, Ge and Si
Authors: Kim Donghyun , Krishnamohan Tejas , Saraswat Krishna
Published: October 2008

We have thoroughly investigated Double Gate (DG) n-MOSFETs with III-V materials (GaAs (111), InP (111), InAs (111) and InSb (111)) and compared to Si (100) and Ge (111). The simulations performed under ballistic transport take into account non-parabolic full band structure, quantum confinement effects, BTBT leakage and SCE effects. Our results show that with oxide thickness of 0.7 nm, despite of small density of states (DOS) of these materials, III-V and Ge outperform Si in terms of drive current and gate delay. However, the high mobility, small bandgap materials like InAs, InSb and Ge, suffer from excessive BTBT current and poor SCE, which limits their scalability. Effect of parasitic gate capacitance in DGFET on device performance is given as well.
Fabrication and Characterization of Suspended Uniaxial Tensile Strained-Si Nanowires for Gate-All-Around Nanowire n-MOSFETs
Authors: Hashemi Pouya , Canonico Michael , Yang Joel K.W. , Gomez Leonardo , Berggren Karl K. , Hoyt Judy
Published: October 2008

Suspended strained-Si nano-wires (NWs) were fabricated from a highly biaxially strained-Si substrate (with an initial stress of 2.16 GPa). Using e-beam lithography, ~25nm thick NWs with the widths in the range of 20 to 80 nm were fabricated and the stress was investigated by UV micro-Raman spectroscopy. Suspended NWs are strained to an average uniaxial tensile stress level of ~2.1 GPa which is almost independent of NW width, in the range studied in this work. Ultra-dense (25 NWs per micron) sub-20 nm suspended strained-Si NWs were fabricated using resolution-enhanced lithography to improve the Raman signal-to-noise ratio. A tensile in-plane stress level of 1.7GPa was measured for 18 nm-wide NWs at 40 nm pitch. Gate-all-around n-MOSFETs were fabricated based on these strained-Si NWs. Electrical measurements on these MOSFETs demonstrate near ideal subthreshold behavior, very high on-to-off ratio and current drive and transconductance enhancement of ~2X over unstrained NWs.
Study on Stress Memorization by Argon Implantation and Annealing
Authors: Hino Masafumi , Nagata Kouki , Yoshida Tetsuya , Kosemura Daisuke , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Ogura Atsushi , Hattori Takeo , Iwai H.
Published: October 2008

The effects of SiN stress film, argon implantation and annealing on the stress of planar and patterned samples were examined. Stress levels changed with SiN films of line-and-space patterned samples can be well characterized by de-convoluting the UV-micro-Raman spectra. Argon implantation caused stress because argon atoms remained in silicon after long-time annealing. Larger stress change in the patterned sample than the planar sample by argon implantation was observed.
Inductively Coupled Ar/CCl2F4 /Cl2 Plasma Etching of Ge
Authors: Kim Taek Sung , Choi Sang-Sik , Jeong Tae Soo , Kang Sukill , Shim Kyu-Hwan
Published: October 2008

We have investigated the etch rates and the angle subtended for Ge as a function of varied Inductively Coupled Plasma (ICP) power, CCl2F2 flow, and Cl2 flow. The etch rate of Ge increases from 374 to 520 Aå/min as ICP power increases from 400 to 700 W, whereas the etching rate of Ge decreases from 524 to 400 Aå/min as CCl2F2 flow increases from 40 to 80 sccm, respectively. Also, the etching rate of Ge decreases from 467 to 400 Aå/min as Cl2 flow increases from 0 to 20 sccm. As ICP power increases the angle subtended also increases. From the SEM photographs it appears that Ar/CCl2F2 /Cl2 ICP etching causes the presence of carbon-based material in the form of large particles.
Liquid Phase Diffusion Growth of SiGe Single Crystals under Magnetic Fields
Authors: Armour Neil , Yildiz Mehmet , Yildiz Emine , Dost Sadik
Published: October 2008

The manuscript presents the results of a combined experimental and modeling study on the Liquid Phase Diffusion (LPD) growth of single crystal SixGe1-x on Germanium with and with the application of magnetic fields. Although the LPD process is mainly diffusion driven through out the growth period, strong natural thermosolutal convection occurs in the first five hours of growth, and the growth interface is concave to the melt. Applied rotating and static magnetic fields were considered to examine the growth and silicon dissolution processes in the LPD system. Results show that the application of a combined applied magnetic is beneficial.
UV and Visible Raman Spectroscopy Applied to sSi/Si1-XGeX and sSOI Stacks
Authors: Rouchon Denis , Hartmann Jean-Michel , Crisci Alexandre , Mermoux Michel
Published: October 2008

Mechanical strain can be used to improve electronic transport properties in advanced short gate length Si-based Metal Oxide Semiconductor Field Effect Transistors. The controlled introduction of strain in the channel area of transistors (thanks to recessed SiGe sources and drains, contact etch stop layers or to previous processing at the wafer scale) can indeed increase the carrier mobility by a factor of up to two. We have used here ultra-violet and visible Raman Spectroscopy to study the processes that can influence strain during the elaboration of strained Si On Insulator (sSOI) substrates. The results obtained during analyses of tensily-strained Si layers grown on polished Si1-xGex virtual substrates (VS) show that the strain can be preserved for 20% of Ge. However, we observed a relaxation of the strain for 40% Ge, after layer transfer onto oxidized silicon. A definite strain relaxation at the edges of lines patterned in sSOI wafers was also demonstrated. A good agreement between experimental results and simulation has been achieved
Enhancement of Local Strain in Si Microstructure by Oxidation Induced Ge Condensation
Authors: Tanaka Masanori , Tanaka Takanori , Sadoh Taizoh , Morioka Jun , Kitamura Tokuhide , Miyao Masanobu
Published: October 2008

Effects of oxidation induced Ge condensation on local strains in Si microstructures induced by the SiGe stressor were investigated. The strain ratio in the Si microstructures increased by the Ge condensation, due to piled-up Ge atoms at SiO2/SiGe interfaces. However, the strains were relaxed by defect generation, if the concentration of piled-up Ge exceeded a critical value (~40%). Thus, a possibility to enhance local strains by oxidation induced Ge condensation was demonstrated.
Extended Defects in Ge-condensed SGOI Structures Fabricated by Using Proton and Helium Implantations
Authors: Kwak Dong Wook , Seo Myung Won , Kim Do Hyung , Lee Dong Wha , Lee Youn Hwan , Cho Hoon Young
Published: October 2008

The SGOI structures using Ge condensation method have been fabricated by rapid thermal chemical vapor deposition using H+ and He+ ion-implantations, and deep level defects investigated using the deep level transient spectroscopy (DLTS). According to DLTS measurement, a deep level defect induced during Ge condensation process was found at 0.28 eV above the valence band with capture cross sections of 2.67x1017 cm-2, and two extended deep levels at 0.54 eV and 0.42 eV above the valence band with capture cross sections of 3.17x1014 cm-2, 0.96x1015 cm-2, respectively. Of ion-implanted samples, the densities of the newly generated defect as well as the existing defects were decreased effectively. And, Coulomb barrier height of the extended defect was drastically reduced. Thus, we suggest that the Ge condensation method using the H+ ion implantation could reduce deep level defects generated from the Ge condensation and control electrical properties of condensed SiGe layers.
Strain in Epitaxial Si/SiGe Graded Buffer Structures Grown on Si (100), Si (110) and Si(111): a Raman Spectroscopy Study
Authors: Rouchon Denis , Destefanis Vincent , Hartmann Jean-Michel , Crisci Alexandre , Mermoux Michel
Published: October 2008

We report preliminary results on the Raman characterization of strained-Si films pseudomorphically grown on (001), (110) and (111) SiGe virtual substrates. Because the relation between strain or stress and the Raman frequencies are complex, we first derive the strain-shift coefficients for the different substrate orientations considered in this work. Then, visible and near-UV Raman spectroscopies were used to extract the in-plane lattice parameter of the virtual substrate and the strain in the thin silicon epitaxial layers grown on top. Finally, we investigated the in-plane strain distribution in strained Si/SiGe buffer layers grown on (110) and (111) silicon substrates by Raman imaging. In-plane strain fluctuations are observed both in the epilayer and the virtual substrate for all substrate orientations.
Regrowth Kinetics Of Self-amorphized Germanium and Evolution Of Implant Damage
Authors: Koffel Stephane , Scheiblin Pascal , Claverie Alain
Published: October 2008

This paper presents the accurate measurement by Transmission Electron Microscopy of the Solid Phase Epitaxial Regrowth of an amorphous Germanium layer. Moreover, these experiments give the proof that End of Range defects form in Germanium during the regrowth of the layer.
Temperature-dependent Operation of Ge on Si p-i-n Photodetectors
Authors: Colace Lorenzo , Balbi Michele , Sorianello Vito , Assanto Gaetano
Published: October 2008

We investigate the temperature dependence of p-i-n photodetectors realized in germanium on silicon. The dark current increases by a factor 1.6÷1.9 every 10oC and is typically dominated by generation in the space charge region, with diffusion contributing in the best samples. The NIR responsivity decreases with temperature in devices with a large defect-density, but is more stable in high quality photodiodes. These findings provide a relevant insight on the design Ge-on-Si NIR detectors to be operated above room temperature
Characterization of Fe3Si/Si Schottky Contact for Future Spin-Transistor
Authors: Kishi Yuji , Kumano Mamoru , Ueda Koji , Sadoh Taizoh , Miyao Masanobu
Published: October 2008

The electrical characteristics of epitaxially grown Fe3Si/Si structures were investigated. From the I-V and C-V measurements, excellent Schottky barrier characteristics (n=1.0, φn=0.62eV) were demonstrated. Moreover, the electrical characteristics did not deteriorate after post-annealing (400oC, 1h), which guaranteed the thermal stability of Fe3Si/Si structures up to 400oC.
Schottky Barrier Height Engineering on NiSiGe/SiGe Contacts
Authors: Tan Cheng Cheh D. , Chua Chee Tee , Chi Dongzhi
Published: October 2008

In this paper, we demonstrate Schottky barrier height adjustment of Nickel-Germanosilicide (NiSiGe) contact on Si0.7Ge0.3 by controlling the As+ implants at the NiSiGe/Si0.7Ge0.3 interface. Various dosage of As+ was implanted into both n- and p- type Si0.7Ge0.3 to demonstrate the control of effective barrier height. Electrical characterization shows ohmic contact can be achieved for NiSiGe on n-Si0.7Ge0.3. We use 2-D XRD to confirm presence of NiSiGe phase and TOF-SIMS to confirm the segregation of As+ doping at the contact-semiconductor interface.
Effect of Strained-Si Layer Thickness on Dislocation Distribution and SiGe Relaxation in Thin Buffer Layer Strained-Si/SiGe Heterostructures
Authors: Lu Jinggang , Rozgonyi George , Seacrist Mike
Published: October 2008

In this paper, defects and strain in SiGe heterostructures with 8, 13, 25, or 40 nm strained-Si (sSi) on top of 300 or 600 nm Si0.77Ge0.23 buffer have been examined. We found that threading dislocations (TDs) in the super-critical thickness sSi samples are more evenly distributed, while they are severely trapped inside TD pileups in the sub-critical thickness sSi samples. Raman spectroscopy revealed that the relaxation degree of the 300 nm SiGe layer decreases from 80% to 67% with the sSi layer increase from 8 nm to 40 nm. This suggests a continuous relaxation of the highly compressively strained, thin SiGe buffer during or even after sSi growth, and its gradual suppression by presence of a tensile strained sSi layer. Based on these observation, we suggest that an in-situ thermal annealing prior to the sSi growth will help to enhance the strain relaxation of thin SiGe buffers.
Engineering SiGe Growth Using Mechanically Responsive Ultrathin Substrates
Authors: Kim-Lee H.-J. , Savage Donald E. , Ritz Clark , Lagally Max G. , Turner Kevin T.
Published: October 2008

A new approach to SiGe island ordering on mechanically responsive silicon nanomembranes (SiNMs) is examined using mechanics modeling. Double-sided deposition on freestanding substrates results in ordered islands on both surfaces. This ordering occurs because the extreme thinness of the SiNM allows islands on one surface to create significant strain fields, which guide the nucleation of subsequent islands, on the opposite surface. The locations of nucleation sites predicted by the modeling agree with experimental observations of SiGe islands grown on silicon nanomembranes. The modeling shows that the island location and the strength of ordering can be controlled by manipulating the thickness of the membrane.
Characterization of Si1-xGex Epilayer Thickness, Ge and Doped Boron Concentration with UV-Vis-IR Spectroscopic Ellipsometer
Authors: Bondaz Alexis , Kitzinger Laurent
Published: October 2008

Spectroscopic Ellipsometry (SE) is a non contact, non destructive approach based on the change of polarisation of light after reflection on a sample. SE allows the precise determination of the refractive indices and thicknesses of the films. With UV-Vis-IR spectroscopic ellipsometer, not only epilayer thickness and Ge concentration can be obtained with the UV-Vis channel, but also p-type dopant concentration with the IR channel. In this presentation, an alloy model will be introduced first to obtain Ge concentration. The principle to determine dopant concentration and electric properties of the film will be given secondly. With the advanced SOPRA ellipsometer tool, four types of samples were characterized, which are (a) single SiGe layer (Box), (b) SiGe layer with Si cap, (c) SiGe layer with graded Ge concentration and (d) Boron doped SiGe layer