bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial Reactions of Copper/Refractory Alloy and Bilayer Films on Si02
Authors: Spreitzer R. L. , Rafalski S.A. , Adams D. , Russell S.W. , Atzmon Z. , Li J. , Alford T.L. , Mayer J.W.
Published: April 2011

We studied interfacial phase formation between copper and copper-alloy films on SiO2 in order to understand how to improve adhesion. CuCr and CuTi alloy and bilayer films on SiO2 were annealed from 400-600°C for 30 min in an N2 + H2 (5%) ambient. The bilayer systems exhibited refractory metal migration from the interface to the surface where they oxidized. In the CuTi bilayer system, an oxidized interfacial Ti layer was observed. Both CuCr and CuTi alloy systems exhibited refractory metal segregation to the interface and surface. Rutherford backscattering spectrometry and Auger electron spectroscopy were used for elemental depth profiling.
Effect of Polishing Pad Material Properties on Chemical Mechanical Polishing (Cmp) Processes
Authors: Bajaj Rajeev , Desai Mukesh , Jairath Rahul , Stell Matthew , Tolles Robert
Published: April 2011

Chemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to “cold flow” and/or “caking” of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness - which itself is dependant upon intrinsic polymer stiffness and cell density.
Reliability Study of On-Chip Interconnects : Prediction of Electromigration Resistance on A Short Time Scale
Authors: De Ceuninck W. , D’Haeger V. , Stulens H. , De Schepper L. , Stals L.M.
Published: April 2011

A new method is presented to evaluate the resistance to electromigration (EM) of on-chip interconnects. The method is based on high resolution in-situ electrical measurements. In this way, the electrical resistance is measured with high accuracy during electromigration at high temperature. After careful analysis of the isothermal results, it was found that the metallization can be characterized by one parameter: the rate of resistance change (RRC). It is shown that the RRC is very sensistive to the electromigration performance. The performance level of the different metallizations can easily be detected and can be qualified in a quantitative way. The results are also compared with classic Mean Time To Failure (MTTF) results and it is found that there exists an almost linear relationship between the RRC results and the MTTF results. However, the in-situ technique offers the benifit that a metallization can be characterized on a time scale as short as a few days, which is certainly not the case for the classical techniques.
Properties of Metal / Polyphenylquinoxaline Interfaces
Authors: Bellard L. , Themlin J.M. , Palmino F. , Cros A.
Published: April 2011

We have investigated the microscopic properties of copper and chromium layers deposited on polyphenylquinoxaline (PPQ). PPQ is a thermostable polymer used for multichip module applications. The metal is deposited under ultra-high vacuum conditions and analysed in-situ by X-ray photoemission (XPS) and atomic force microscopy (ex situ). Copper does not react significantly with the PPQ and tends to diffuse into the polymer matrix upon annealing. On the contrary, chromium strongly reacts with the polymer surface at room temperature. With increasing metal coverage, chromium grows in a layer-by-layer mode and the reacted interface is progressively burried under the pure metal layer.
High Density Magnetically Confined Dry Etching of Metallization and Dielectrics in Gaas Device Technology
Authors: Pearton S. J. , Abernathy C. R. , Ren F. , Lothian J. R. , Kopf R. F. , Katz A.
Published: April 2011

Dry etching of common masking materials used in GaAs device technology was examined down to temperatures of −30°C. The etch rates of SiNx, SiO2 and W in SF6/Ar are reduced below 0°C, but the anisotropy of the etching is improved at low temperature. Microwave enhancement of the SF6/Ar discharges produces increases in etch rates of several times at 25°C, but much lower increases at −30°C substrate temperature. The underlying GaAs surface shows increased S and F coverage after low temperature etching, but these species are readily removed either by an ex-situ wet chemical cleaning step or an in-situ H2 plasma exposure. Photoresist etching is less sensitive to temperature and anisotropic profiles are produced between −30 and + 60°C in pure 02 discharges.
Photoresponse Study of Polycrystalline Diamond thin Film Schottky Diodes
Authors: Zhao G. , Stacy T. , Charlson E. M. , Charlson E. J. , Hajsaid M. , Roychoudhury R. , Khan A. H. , Meese J. M. , He Z. , Prelas M.
Published: April 2011

We are reporting the first quantitative photoresponse characteristics of boron doped hot-filament CVD (HFCVD) diamond based Schottky diodes using semi-transparent aluminum contacts in the spectral range of 300–1050 nm. Quantum efficiencies, obtained without correction for surface reflection in the visible and near UV region, were between 5 % and 10% when the diodes were unbiased. Effect of reverse bias on the photoresponse was investigated at selected photon energies. Reverse biased diodes exhibit increasing photoresponse and ultimately saturation. Quantum efficiency as high as 30% was also obtained at 500 nm, when a reverse bias of over I volt was applied. The photoresponse mechanism of CVD diamond Schottky diodes is also discussed. A Schottky barrier height of 1.15 ± 0.02 eV for Al-HFCVD diamond contacts was determined using the d.c. photoelectric method.
Comparison of Thermal Gate Oxides on Silicon and Carbon Face P-Type 6H Silicon Carbide
Authors: Zetterling Carl-Mikael , Östling Mikael
Published: April 2011

Monocrystalline 6H silicon carbide samples (n-type and p-type) with both carbon face and silicon face have been used to investigate gate oxide quality. The oxides were thermally grown in a dry oxygen ambient at 1523 K with or without the addition of TCA (Trichloroethane), or in wet pyrogenic steam at 1473 K. POCI3 doped polysilicon gates were used for electrical characterisation by capacitance-voltage measurements and breakdown field measurements. Large flatband voltage shifts indicate fixed oxide charges up to 1013 cm-2. The incorporation of aluminum in the oxides was monitored using SIMS (Secondary Ion Mass Spectrometry). Surprisingly high signals were interpreted as evidence of an aluminum-Oxygen compound having been formed (ie Al2O3).
Summary of Panel Discussion “Substrate Issues for Wide Bandgap Semiconductors”
Authors: Yoder Max N. , Bachmann Peter K.
Published: April 2011

The state-of-the-art in each of the major materials (Diamond, SiC and III-nitrides) was discussed with the advantages, disadvantages, and requirements of each enumerated.
Process Analysis of AP-CVD of Silicon Carbide
Authors: Rottner K. , Helbig R.
Published: April 2011

The growth of SiC epilayers by atmospheric pressure CVD (AP-CVD) is influenced by many chemical gas phase reactions and transport phenomena, and is difficult to study directly due to the high growth temperatures (up to 2100 K). To grow epilayers of good quality, it is necessary to control the silicon and carbon supply, each affected by different mechanisms. The use of graphite as the susceptor material causes a remarkable change in the carbon balance due to reactions between the graphite and the hydrogen carrier gas. This graphite-hydrogen reaction enriches the gas phase with carbon and above a certain critical temperature it is impossible to control the Si:C-ratio in the gas phase by a variation of the carbon containing input gas. The silicon supply is usually treated as transport through a stagnant layer in the gas phase determined by the transport properties of the carrier gas and the temperature gradient in the reactor. A numerical solution of the flow-equations in the reactor shows that the flow characteristics and temperature gradients in the reactor are hardly affected by the gas flow velocity.
Laser Transformed SiC Thin Films
Authors: Kreider K. G. , Burgess D. R. F. , Tarlov M. J. , Gillen G. , Wight S. , Lareau R. , Casas L. M.
Published: April 2011

Silicon carbide has excellent physical and electronic properties for use in devices when higher temperatures or higher power densities are required. We have investigated a direct laser conversion technique to create electrical conductors on the high band-gap silicon carbide. Thin films of silicon carbide (SiC) were sputter deposited on AI2O3, SiO2, and Si substrates using a SiC target with an RF planar magnetron. These films were irradiated at 308 nm with multiple 15 ns excimer laser pulses creating 0.5 to 2 mm wide electrically conducting paths. Both the irradiated and unirradiated films were evaluated as a function of substrate type, deposition temperature, finish, stoichiomelry, annealing temperature, sputter gas, film thickness, and laser processing conditions. The lowest resistivity films, originally 10 ohm-m, were calculated to be 160 μohm-m obtained after irradiation, which compares to a value of 50 μohm-m obtained after irradiating bulk SiC. The films were characterized using XPS, SIMS, AES, SEM, and Raman spectroscopy. We were able to characterize the composition of the films and conducting traces, the surface oxide, the critical binding energies, the lattice structure, and the morphology of the microstructure. Models for the phase transformations and conductivity have been formulated.
Fundamental Materials-Issues involved in the Growth of GaN by Molecular Beam Epitaxy
Authors: Newman N. , Fu T.C , Liu X. , Liliental-Weber Z. , Rubin M. , Chan J. S. , Jones E. , Ross J. T. , Tidswell I. , Yu K. M. , Cheung N. , Weber E. R.
Published: April 2011

Gallium nitride is one of the most promising materials for ultraviolet and blue light-emitting diodes and lasers. Both Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) have recently made strong progress in fabricating high-quality epitaxial GaN thin films. In this paper, we review materials-related issues involved in MBE growth. We show that a strong understanding of the unique meta-stable growth process allows us to correctly predict the optimum conditions for epitaxial GaN growth. The resulting structural, electronic and optical properties of the GaN films are described in detail.
Structural Characterization of GaN Grown By Electron Cyclotron Resonance-Metalorganic Molecular Beam Epitaxy (ECR-MOMBE)
Authors: Bharatan S. , Jones K. S. , Pearton S. J. , Abernathy C. R. , Ren F.
Published: April 2011

Electron cyclotron resonance-metalorganic molecular beam epitaxy (ECR-MOMBE) has been used to deposit cubic and hexagonal gallium nitride (GaN) on various substrates, namely GaAs, ZnO and Al2O3. This paper will report on the effect of the growth rate of the GaN layer on the surface morphology, as analyzed using scanning electron microscopy (SEM). Structural characterization of this material was conducted using cross-sectional transmission electron microscopy (XTEM) and x-ray diffraction. Conditions such as pre-deposition annealing, growth rate and growth temperature are critical in determining the phase and crystallinity of the deposited layers. These parameters were optimized to obtain the cubic GaN phase on GaAs substrates and single crystal wurtzitic GaN on ZnO and Al2O3 substrates.
Raman Scattering and X-Ray Diffraction Studies of Gallium Nitride Films Grown on (100) Gallium Arsenide
Authors: Brown S. W. , Rand S. C. , Hong C.-H. , Pavlidis D.
Published: April 2011

Raman spectroscopy and x-ray diffraction are used to characterize Gallium Nitride (GaN) films grown on (100) Gallium Arsenide (GaAs) substrates. Reflection X-ray diffraction data from (200) planes of GaAs and cubic GaN are presented. The linewidth of the cubic GaN diffraction peak is shown to be a strong function of the growth temperature. Raman spectra are presented for a series of samples grown at different temperatures. Raman scattering is characterized by strong peaks at 560 cm-1 and at 736 cm-1, corresponding to TO and LO phonon modes of cubic GaN, respectively. An additional, unexplained feature at 768 cm-1 is clearly observed in Raman spectra of c-GaN samples grown at lower temperatures. The polarization dependence of the intensity of the GaN LO phonon mode is presented and compared with the GaAs LO phonon mode to establish the relative orientation of the c-GaN epitaxy on GaAs.
IR-Absorption Spectra of Impurities in 6H-SiC
Authors: Engelbrecht F. , Helbig R.
Published: April 2011

We performed infrared absorption and reflectivity measurements on serverai 6H-SiC samples at variable temperatures between T=5K and T=300K. From the temperature dependence of the observed absorption lines we separated electronic from vibronic transitions. The electronic transitions are assumed to be due to transitions from the neutral nitrogen donor occupying the three different carbon lattice sites in 6H-SiC into excited states. We determined polarization and the oscillator strengths of these transitions. From the temperature dependence of the electronic transitions we determined the valley-orbit-splitting energy and we demonstrated the influence of compensation. For the different vibronic transitions we determined the Grüneisen constants.
Correlations Between Electrical and Material Properties of CVD Diamond
Authors: White C. , Zhao S. , Gan K. K. , Kagan H. , Kass R. , Malchow R. , Morrow F. , Palmer W. , Han S. , Kania D. , Pan L. S. , Schnetzer S. , Stone R. , Teserek R. , Angus J. , Ma S. J. , Sugimoto Y.
Published: April 2011

The electrical properties associated with diamond charged particle- and photo-detectors were studied using charged particle-induced conductivity (CPIC) and photo-induced conductivity (PIC). The collection distance d, the product of the excess carrier mobility μ excess carrier lifetime T and electric field E, was used to characterize the diamonds. X-ray diffraction, Raman spectroscopy, photoluminescence, SEM and TEM were performed on CVD diamond detectors to investigate the limitations of the electrical properties. Correlations were found between the electrical properties and the material characterizations.
Conductivity Anisotropy in Epitaxial 6H and 4H Sic
Authors: Schaffer William J. , Negley G. H. , Irvine K. G. , Palmour J. W.
Published: April 2011

A measure of the electron mobility anisotropy in n-type 4H and 6H-SiC has been obtained using the Hall effect over the temperature range 80K<T<600K. Hall mobility and resistivity data are collected from appropriately oriented bar patterns fabricated into high quality epitaxial material grown on (1100) or (1120)surfaces having total impurity concentrations 1017-1018 cm-3. The observed mobility ratio for 4H is μ[1120]/[0001] and is independent of temperature. For 6H, the ratio μ[1100]/[0001] decreases from ∼6.2 at 80K to ∼5.0 at 150K and is essentially constant (∼4.8) above 200K. A donor level near 0.6 eV is occasionally observed in 4H which reduces the high temperature electron mobility and introduces an apparent temperature dependence to the mobility ratio if nonuniformly distributed.
Diffusion of Impurities Under Bias in CVD Diamond Films
Authors: Popovici G. , Sung T. , Prelas M. A. , Khasawinah S. , Wilson R. G.
Published: April 2011

The diffusion of oxygen, lithium, chlorine, and fluorine in CVD diamond films was performed under bias at 700 and 1000 °C. SIMS and Auger analyses were used to determine the impurity concentration. After diffusion, the concentrations of Li and O in the diamond films were found to be of the order of (3–4)×1019 cm-3. The fluorine concentration was of order of (l-2)×1017 cm-3. The conductivity was p-type. The change in the resistivity due to diffusion was nearly nine orders of magnitude for the sample diffused under electric field, and six orders of magnitude for the samples diffused without field. No dependence of the impurity concentration on the applied bias was observed except for fluorine. The fluorine concentration dependence on the electric field indicates that fluorine may have formed a shallow level in the diamond band gap. The fact that large concentrations of impurities can be diffused into diamond films at relatively low temperatures indicates the presence in the films of many lattice defects (including grain boundaries).
Band-Offsets Between Group-III-Nitrides
Authors: Albanesi E. A. , Lambrecht W. R. L. , Segall B.
Published: April 2011

The valence-band offset at the zincblende AIN/GaN. AIN/InN and InN/GaN (110) interfaces are calculated self-consistently by means of the linear muffin-tin orbital method using up to 5+5 layer supercells. All interfaces have a type I-offset. Assuming interface orientation and polytype effects on the valence-band maximum to be reasonably small, a type I offset can also be expected for wurtzite interfaces. Our results are in very good agreement with experimental values for AIN/GaN, the only nitride interface for which they are available.

Subject index terms: band offsets, interfaces, hetero junctions, superlattices. III-nitrides.
Nickel Related Absorption Lines in High-Pressure Synthetic Diamond
Authors: Nazaré M. H. , Lopes J. C. , Kanda H.
Published: April 2011

Diamonds grown by the temperature gradient method using a nickel catalyst show an optical absorption band, extending from 2.5 eV to 2.56 eV, with a zero-phonon line at 2.51 eV. At 4 K this line exhibits fine structure; it is made up of 3 components at 2.509 eV, 2.510 eV and 2.511 eV. In absorption the fine structure components have the same relative intensity at different temperatures. We report on the effects of uniaxial stress on the zero-phonon transition at 77 K. We propose an interpretation of the results according to which the optical defect has a tetrahedral symmetry, and the 2.51 eV line occurs between two T2 states.
Native Defects and Impurities in Cubic and Wurtzite Gan
Authors: Neugebauer Jö;Rg , Van De Walle Chris G.
Published: April 2011

Using state-of-the-art total energy calculations we investigate defect formation energies and electronic structure for native defects in wurtzite and cubic GaN.The defect formation energies and electronic structures are very similar in both structures. The main difference is a split in the p-like defect states in wurtzite GaN, which are degenerate in cubic GaN.|The role of the Ga 3d electrons on the chemical bonding in GaN is discussed in detail. We explain why the deep lying Ga 3d electrons have a remarkably strong influence on defect formation energies and atomic relaxation for some of the defects.
Characterization Of sic Layer Formed by C Ion Implantation ( ESR And IR Studies)
Authors: Show Y. , Izumi T. , Deguchi M. , Kitabatake M. , Hirao T.
Published: April 2011

Characterization of C ion implanted silicon layers were performed by fourier transformation infrared ( FT-IR ) spectroscopy and electron spin resonance ( ESR ) methods. Microcrystalline β-SiC including amorphous Si are formed in the Si surface region by annealing at 1200 °C following hot ( 450 °C ) implantation. The ESR analysis revealed the presence of two kinds of defect centers in SiC layer formed by implantation, i.e. Si dangling bond ( g=2.0060, ΔHpp=6 Oe) in the amorphous Si and Si dangling bond with C atom neighbors ( g=2.0032, ΔHpp=3 Oe). Heating substrate during implantation prevents the formation of carbon clusters on the Si surface.
Tight-Binding Study of the {211} Σ=3 Grain Boundary in Cubic Silicon-Carbide
Authors: Kohyama M. , Yamamoto R.
Published: April 2011

In grain boundaries in compound semiconductors such as SiC, the interface stoichiometry and the wrong bonds between like atoms are of much importance. Firstly, a general definition of the interface stoichiometry in such grain boundaries has been discussed. Secondly, the atomic and electronic structures of the {211} Σ=3 boundary in SiC have been examined by using the self-consistent tight-binding method, based on the atomic models with bonding networks similar to those in the models of the same boundary in Si or Ge. The wrong bonds have significant effects through the large electrostatic repulsion and the generation of localized states as well as those in the {122} Σ=9 boundary in SiC. And the different bond lengths of the wrong bonds very much affect the local bond distortions at the interfaces, which determines the relative stability among the present models.
Sulfide Passivated GaAs/AlGaAs Microdisk Lasers
Authors: Hobson W. S. , Mohideen U. , Pearton S. J. , Slusher R. E. , Ren F. , Schnoes M. Lamont
Published: April 2011

Sulfide passivation of optically pumped GaAs/AlGaAs microdisks (at 77K) was examined. The microdisks had diameters between 2 and 10 µm and thicknesses of 0.2 µm. The layer structure was grown by organometallic vapor phase epitaxy. An ammonium sulfide solution was used for the passivation. The GaAs/AlGaAs microdisks without the sulfide treatment did not lase when optically pumped, even at the highest pump power densities of 10 kW/cm2. With sulfide treatment cw lasing was achieved with a lifetime of several seconds. A dramatic increase in the laser lifetime was obtained when the sulfide treated samples were encapsulated with silicon nitride in order to prevent loss of sulfur and surface oxidation. In addition to the lifetime increase, the laser output could be increased by nearly an order of magnitude by annealing at 400°C for 300 s or by cw operation over a period of hours at pumping powers near 10 kW/cm2.
Characterization and Control of Surface Morphology and Defect Density for MBE GaAs Surfaces in the Production MBE Environment
Authors: Patterson George A. , Chang James S.C.
Published: April 2011

In the production MBE environment it is important to maintain low densities of oval defects and particle induced defects in epitaxial films that are used for the fabrication ofGaAs ICs. Most often, the grown layers are characterized on a sample basis by use of an optical microscope. The disadvantages of this technique are the time and labor involved.The data obtained is incomplete, dependent on training, and subjective. A preferred method would be to develop an inspection method that characterizes the surface morphology ofall MBE grown GaAs wafers and the resulting defect density. The use of a laser wafer surface scanning system has allowed us to reproducably inspect 100% of wafers. Rapid diagnosis of epitaxial problems has resulted in an improved understanding of how to routinely produce high quality epitaxial films for GaAs IC production. This work will highlight the production benefits derived from employing 100% inspection of MBE grown GaAs wafers and provide 2D maps. The relationship between gallium source operation and defect sizes will be discussed.
AFM and STM Studies of Large Scale Unstable Growth Formed During GaAs (001) Homoepitaxy
Authors: Orme C. , Johnson M.D. , Leung K.T. , Orr B.G.
Published: April 2011

Atomic force and scanning tunneling microscopy studies have been performed on GaAs(001) films grown by molecular beam epitaxy. Multilayered mounds are seen to evolve when the growth conditions favor island nucleation. As the epilayer thickness is increased, these features grow in all dimensions but the angle of inclination remains approximately constant at 1°. The mounding does not occur on surfaces grown in stepflow. We propose that the multi-layered features are due to an unstable growth mode which relies on island nucleation and the presence of a step edge barrier.
Doping in III-V Semiconductors
Authors: Schubert E. F.
Published: April 2011

Doping of III-V semiconductors is an essential part of growth and processing technology for optoelectronic and high speed electronic devices. This review covers several recent developments in III-V doping including (i) the high-concentration regime for p-type dopants in InP and GaAs, (ii) the sensitivity of doping incorporation on the crystal orientation, (iii) compensation mechanisms in Si-doped GaAs, and (iv) p-type carbon doping in GaAs and AlxGa1-xAs.
The Relationship between InGaAs Channel Layer Thickness and Device Performance in High Electron Mobility Transistors
Authors: Meshkinpour M. , Goorsky M. S. , Streit D. C. , Block T. , Wojtowicz M. , Rammohan K. , Rich D. H.
Published: April 2011

The performance of InGaAs/GaAs pseudomorphic high electron mobility transistors is anticipated to improve with increased channel thickness due to reduced effects of quantum confinement. However, greater channel thicknesses increase the probability of forming misfit dislocations which have been reported to impair device properties. We characterized the composition and thickness of the active layer in Al0.25Ga0.75As / In0.21Ga0.79As structures with different channel thicknesses (75 Å - 300 Å) to within ± 0.005 and ± 8 Å using high resolution x-ray techniques. We determined, using Hall and rf measurements, that the device properties of these structures improved with increasing thickness up to about 185-205 Å; degraded properties were observed for thicker channel layers. Cathodoluminescence results indicate that the mosaic spread observed in x-ray triple axis rocking curves of these device structures is due to the presence of misfit dislocations. Thus, even though misfit dislocations are present, the device structure performs best with a channel thickness of ∼185 Å. These results demonstrate that one can fabricate functional devices in excess of critical thickness considerations, and that these x-ray techniques provide an effective means to evaluate structural properties prior to device processing.
Influence of Growth Parameters on the Properties of InxGa1-xAs Grown on GaAs by OMVPE
Authors: Dyk E. Ernest Van , Leitch Andrew W. R. , Ehlers Hendrik L.
Published: April 2011

InxGa1-xAs epilayers (x < 0.2) have been grown on GaAs substrates by atmospheric pressure OMVPE. The effects of varying the substrate temperature and the gas composition on the properties of the epilayers were investigated. The investigations have shown that higher mobilities were obtained at low growth temperatures (610°C), while optimum optical properties were obtained at higher growth temperatures (690°C). Variation of the AsH3 overpressure yielded optimum electrical and optical properties at a V/III ratio of 50. 77 K mobilities higher than 42 000 cm2/V.s and photoluminescence linewidths as low as 4.4 meV were obtained for x = 0.087 and x = 0.137 epilayers, respectively.
Surface Morphology of InxGa1-xAs/GaAs Relaxed Layers Characterized by Atomic Force Microscopy
Authors: Padeletti G. , Ingo G. M. , Imperatori P.
Published: April 2011

Ga0.65In0.35As layers of a varying nominal epilayer thickness (10 – 1000 nm) have been grown by the MBE technique on GaAs (100) substrates and characterized by the combined use of atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). The surface roughness and morphology have been investigated. The GIXD and AFM results show that the thinnest films are characterized by an asymmetric strain relaxation along the two <110> directions with no surface crosshatched pattern but with a misfit dislocation network. AFM images on the thickest films show also well-oriented protrusions along the [110] direction, which increase in size and become more elongated as the nominal film thickness increases.
Modeling of InGaAs optical constants and its application to spectroscopic ellipsometry study of strained InGaAs/AlGaAs based structures
Authors: Yakovlev V. A.
Published: April 2011

There is a broad spectrum of electronic devices, e.g., high electron mobility, heterojunction bipolar (HBTs) and modulation doped field effect (MODFETs) transistors, and optoelectronic devices, e.g., low-threshold quantum-well (QW) lasers, which employ strained InyGa1-yAs layers to improve device performance due to the enhanced flexibility in the electronic structure. These devices have very promising applications. For example, the ultra-low threshold lasers are going to play a major role in computer interconnect circuits due to their low-power consumption. Strainlayer InGaAs/GaAs QW lasers are of considerable interest as a possible candidate for pumping the upper states of Er-doped silica fiber amplifiers of optical networks.
Effects of Low-Temperature Grown GaAs Intermediate Layers on the Crystalline Quality of GaAs-on-Si Epilayers
Authors: Chong T.C. , Phua C.C. , Lau W.S. , Tan L.S.
Published: April 2011

The incorporation of low-temperature (LT) GaAs intermediate layers grown at 230°C had been shown to have the effects of improving the crystalline quality of GaAs epilayers on Si. The use of this LT-GaAs intermediate layer between the GaAs nucleation layer and the GaAs overlayer has improved the photoluminescence (PL) peak intensity by about five times, and reduced the GaAs (004) X-ray diffraction full width at half maximum (FWHM) by 59 arcsecs. The PL results were subsequently confirmed by cathodoluminescence images. The dominant deep level electron trap in the LT-GaAs epilayer grown on Si substrate was the same as that found in LT-GaAs epilayer grown on GaAs substrate.
TEM Study of MOCVD Grown InSb/GaAs Heterostructures with and without TMIn Predeposited Layers
Authors: Kuo L. H. , Hua Susan Z. , Salamanca-Riba L. , Partin D. L. , Green L. , Heremans J.
Published: April 2011

High quality InSb epilayers were grown on GaAs substrates by metal organic chemical vapor deposition using a two-step growth procedure involving trimethal indium (TMIn) predeposition. From transmission electron microscopy studies, we found that an interdiffusion layer of thickness of 10 Å forms at the interface when the substrate is exposed to TMIn for approximately 6 secs prior to the growth of the InSb filns. Hall mobilities up to σ 52,000 cm2/V-s were obtained at 300 K on a 2.1-μm-thick InSb heteroepitaxial film. In contrast, samples without TMIn predeposition showed polycrystallinity of the InSb films grown on single crystalline GaAs substrates. The effect. of TMNIn predeposition is to minimize the misorientation of the grains, suppress the polycrystallinity, decrease the density of threading dislocations, and increase the electron mobilities in the films. However, we found that too much TMIn predeposition gives rise t.o an intermixing layer at the InSb/GaAs interface which deteriorates the film quality. Details of the effect of the TMIn predeposition on the microstructure of InSb/GaAs with different predeposition times (zero, 6, and 12 secs) are discussed.
A Monte Carlo Model of GaAs [111]B Epitaxy
Authors: Dorsey Donald L. , Venkatasubramanian R. , Yen M.Y. , Haas T.W.
Published: April 2011

The Monte Carlo (MC) technique has been frequently used to model semiconductor thin-film epitaxy, especially for the cases of homo-epitaxial growth on Si (100) and GaAs (100) surfaces. In a recent paper, it was shown that excellent qualitative agreement can be obtained between the surface step density evolution as simulated by a simple cubic MC model and the experimentally observed RHEED specular intensity oscillations on stepped GaAs (100) substrates during growth by MBE [1]. The simple cubic model performs well for this case because of the rectangular arrangement of the gallium atoms in the (100) planes of the gallium sublattice. For the case of the (111) surface, however, the gallium atoms in the (111) plane of the gallium sublattice are hexagonally arranged. This system is not amenable to simulation with a simple cubic MC model. In this work, GaAs [111]B epitaxy is modeled using the MC method on a zincblende lattice. To ourknowledge this is the first application of this technique to the growth of a zincblende thin-film in the [11]B direction..The predicted surface step density evolution is compared to experimental RHEED specular intensity oscillations. The relative merits of using on-axis and off-axis substrates are explored.
Molecular Beam Epitaxy of II/VI Compounds for Blue/Green Laser Diodes
Authors: Gaines J.M.
Published: April 2011

The growth of I1/VI epitaxial layers by molecular beam epitaxy (MBE) for blue/green lasers is described. To elucidate the issues in the growth of II/VI materials, the differences between II/V and II/VI MBE growth are addressed, including factors such as: substrates, molecular beam sources, lattice matching, sticking coefficients, and surface diffusion. Results of reflection high-energy diffraction (RHEED) oscillation measurements are presented. RHEED oscillations have proven to be a valuable in-situ tool for controlling certain aspects of 1I/VI MBE growth, such as ZnSySe1-y composition, Zn1-xMgxSe composition, and the growth rate of ZnSe during migration-enhanced epitaxy.
MBE Growth and Characterization of II-VI Blue/Green Laser Diodes Having CW Operation at Room Temperature
Authors: Ringle M.D. , Grillo D.C. , Fan Y. , He L. , Han J. , Gunshor R.L. , Salokatve A. , Jeon H. , Hovinen M. , Nurmikko A.V. , Hua G.C. , Otsuka N.
Published: April 2011

We have obtained continuous-wave laser operation at room temperature from a (Zn,Mg)(S,Se)-based Il-VI separate-confinement heterostructure where injection of holes into the p-type quaternary was achieved through the employment of a Zn(Se,Te) graded-bandgap contact. The laser devices exhibit threshold current densities of below 300 A/cm2 and voltages below 6 V. Issues related to the control of the growth of the quaternary (Zn,Mg)(S,Se) compound, and a proposal to further reducing the laser operating voltage will also be described.
N- and P-Type Doping of ZnSe Using Gas Source Molecular Beam Epitaxy
Authors: Fisher P. A. , Ho E. , House J. L. , Petrich G. S. , Kolodziejski L. A. , Brandt M. S. , Johnson N. M.
Published: April 2011

High quality ZnSe:Cl has been grown on GaAs by gas source molecular beam epitaxy (GSMBE); elemental Zn and H2Se are used as source materials, with ZnCl2 as a dopant source for donors. Atomic Cl concentrations ([Cl]) approaching 1020 cm−3 have been incorporated into the lattice as indicated by secondary ion mass spectrometry (SIMS). At incorporation levels greater than 1020 cm−3, an appreciable decrease in the growth rate has been observed. The sharp transition to a negligible growth rate is attributed to the occurrence of a surface chemical reaction originating from Cl and H which are present in the GSMBE environment. For [Cl] as high as 4 x 1018 cm−3, the films exhibited high crystalline quality, as indicated by photoluminescence originating from a single intense donor-bound excitonic transition. Hydrogenation of semiconductors can potentially result in the electrical passivation of incorporated acceptor and donor species. In the case of ZnSe:Cl, H was present in the ZnSe layers, but did not appear to adversely affect the electrical properties of the n-type films. In contrast, for the growth of ZnSe:N, where a nitrogen plasma cell was employed as a source of nitrogen, the H concentration (as determined by SIMS) was observed to track the N concentration. The ZnSe:N films were highly resistive for various amounts of N incorporation, which suggests that H incorporation is an issue of primary importance in the p-type doping of ZnSe grown by GSMBE.
Highly Doped P-Type and N-Type ZnS, ZnSe, CdS and CdSe Thin Films Growth by Pulsed Laser Deposition
Authors: Shen Wenpin P. , Kwok Hoi S.
Published: April 2011

ZnS, ZnSe, CdS and CdSe thin films were grown on InP or GaAs substrates with high ptype and n-type doping concentrations by pulsed excimer laser deposition without any postannealing processing. The x-ray diffraction results showed that these thin films were fully epitaxial (in-plane aligned). These high quality films are suitable for use as optoelectronic devices which will operate in the visible region of the spectrum.
Thermal Expansion Behavior of ZnSe and ZnS0.03Se0.97 Epilayers on GaAs at Temperatures in the Range, 25°C - 250°C
Authors: Kim J. R. , Park R. M. , Jones K. S.
Published: April 2011

The thermal expansion behavior of ZnSe and ZnS0.03Se0.97 epilayers grown on GaAs has been investigated using high resolution X-ray diffraction at temperatures between room temperature and the growth temperature. The lattice parameters perpendicular and parallel to the surface were measured with the Bond's method. The lattice mismatch for a partially relaxed ZnSe layer was Δa(⊥)/a =2300 ppm and Δa(‖)/a = 2600 ppm at room temperature(R.T.) and Δa (⊥)/a =3600 ppm and Δa(‖)/a =2400 ppm at 250°C. For ZnS0.03Se0.97 which is almost lattice matched at R.T. to GaAs, Δa(⊥)/a =200 ppm, Δa(⊥)/a =20ppmatR.T. and Δa(⊥)/a =1400ppm, Δa(⊥)/a =50ppm at 250°C. The relaxed lattice constants were evaluated and the thermal expansion coefficients of relaxed ZnSe layers were found to vary from 7.8*10−6/°C at room temperature to 12.2*10−6/°C at 250°C and for ZnS0.03Se0.97 layers the variation was from 7.5*10−6/°C at R.T. to 11.7*10−6/°C at 250°C.
MOCVD Growth and Characterization of High-Quality ZnSe on GaAs
Authors: Chen J. C. , Yang Bing , Semendy F. , Clark W. W. , Boyd P. R. , Bambha N.
Published: April 2011

High-quality ZnSe epilayers on GaAs substrates have been grown by MOCVD. Diethylzinc (DEZn) and diethylselenide (DESe) were used as source materials. Growth studies were done at 400°C under different growth conditions in an atmospheric pressure MOCVD reactor. The as-grown ZnSe epilayers were characterized by a wide variety of techniques, such as double crystal x-ray diffraction, low-temperature photoluminescence (PL), transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), and scanning electron microscopy (SEM).

The results show excellent structural and optical properties of ZnSe. The best material was grown on undoped GaAs at the VI/II ratio near unity. The full-width-at-half-maximum (FWHM) of ZnSe (∼0.2/μm thick) x-ray peak as low as 90 arc seconds was achieved. TEM results also show very low defect density. The density of stacking faults is less than 105/cm2 which is four orders of magnitude less than that of samples grown by conventional MBE [J. Petruzzello et al. J. Appl. Phys. 63, 2299 (1988)] and MOCVD [J.L. Batstone et al. Philos. Mag A, 66, 609, 1992]. The spacing between misfit dislocations is between 5 to 10,μm which is one order of magnitude larger than that of reported sample of comparable thickness.
Optical and X-Ray Diffraction Characterization of MBE-Grown InGaAs, InAlAs and InGaAIAs on InP
Authors: Feng Z. C. , Chua S. J. , Raman A. , Lim N.N.
Published: April 2011

A variety of Inl-xGaxAs, Inl-yAlyAs and Inl-x-yGaxAlyAs films have been grown on InP by molecular beam epitaxy. A comprehensive characterization was performed using Raman scattering, photoluminescence (PL), Fourier transform infrared (FTIR) spectroscopy and double crystal X-ray diffraction on these ternary and quaternary heterostructures with different compositions and growth conditions. The lattice matched and mismatched structures are studied. Our analyses show that the interface mismatch exerts an important influence on the optical properties of these heterostructures, and conversely that Raman, PL and FTIR can be used to probe the interface mismatch nondestructively.
Current State and Future Challenge in HgCdTe MBE Technology
Authors: Wu Owen K.
Published: April 2011

Significant progress has been made in HgCdTe MBE technology over the last two years. Device quality materials have been grown with the alloy compositions required for short-wavelength infrared (SWIR), 1-3 micron to LWIR (long-wavelength infrared), 8-12 micron applications. Indeed, the observation of low defect density (EPD<2×105/cm2), long minority carrier lifetime and efficient IR photoluminescence attests to the device quality of HgCdTe epilayers grown by MBE. In addition, the breakthroughs to achieve In (N-type) and As (P-type) doping in situ have provided greater flexibilities for fabricating advanced heterojunction devices. High performance IR imaging arrays have been fabricated and IR images were obtained. Also, dual-band detectors and injection infrared diode lasers which have been demonstrated recently are considered. Finally, additional developments and the future challenges in HgCdTe MBE technology are discussed.
MBE Regrowth Over a Selectively Undercut GaAs Masking Layer
Authors: Hansing C.C. , Deng H. , Reifsnider J.M. , Deppe D.G. , Streetman B.G.
Published: April 2011

We describe the use of molecular beam epitaxy (MBE) for regrowth over a photolithographically defined GaAs shadow mask to fabricate a buried etched void surrounding a vertical-cavity surface-emitting laser (VCSEL). The initial MBE growth consists of a GaAs etch stop layer, followed by an Al0.67Gao.33As spacer layer, and then a GaAs capping layer. After the initial growth, various diameter openings ranging from 2 to10 gtm are photolithographically defined in a photoresist layer, and the top GaAs layer is selectively etched. The exposed LTAlGaAs layer is next selectively etched with the etch time adjusted to undercut the top GaAs layer to create a shadow mask. An MBE regrowthis then performed which consists of alternating layers of GaAs and AlAs. Scanning electron microscopy, surface profiling, and optical microscopy are used to characterize the regrowth.

We have used this shadow masking technique to realize a buried etched void surrounding the optically active part of a VCSEL. A continuous wave room temperature lasing thresholdof 0.47 mA for a 4 [tm device has been achieved, which to our knowledge is the lowest continuous wave room temperature threshold yet reported for a VCSEL.
Texture Development in Thin Nickel Oxide Films
Authors: Czerwinski F. , Szpunar J.A.
Published: April 2011

X-ray diffraction was used to study the influence of ultra-fine dispersions of CeO2 on the texture development and epitaxial relationships in oxide films, formed at high temperatures. The substrate orientation exerted the essential effect on microstructure and growth rate of oxide films on both pure as well as coated nickel. NiO grown on (100)Ni was polycrystalline with grains randomly oriented. Applying of CeO2 resulted in a marked decrease of the oxide growth rate without significant changes in the texture. The NiO formed on pure (111)Ni exhibited strong (111) texture. During initial stages of oxidation the presence of CeO2 caused the nucleation of randomly oriented oxide. However, the oxide developed during further exposure had the same character as that grown on pure (111)Ni face. X-ray measurements are compared with analysis conducted by TEM and electron microdiffraction. The role of chemically active element in inhibition of diffusion processes during the growth of oxides on both crystal faces is discussed.
Investigating the Role of Grain Boundaries in Interface Reactions
Authors: d'Heurle FranÇois M , Gas Patrick , Philibert Jean
Published: April 2011

The paper is built around a nonexhaustive review of the literature on the role of grain boundaries in reactive phase formation. Examples are chosen to illustrate these effects in silicide and oxide growths, and later on in metal-metal interactions. A short section deals with the effect of grain boundaries and grain boundary adsorption of impurities on the kinetics of growth and on the morphology of the growing layer. Some attempts at understanding the mechanisms of phase growth from the tracking of isotopes are briefly analyzed.
Grain Growth in Polycrystalline Thin Films
Authors: Thompson Carl V.
Published: April 2011

The performance and reliability of polycrystalline films are strongly affected by the average grain size and the distribution of grain sizes and orientations. These are often controlled through grain growth phenomena which occur during film formation and during subsequent processing. Abnormal rather than normal grain growth is most common in thin films, and leads to an evolution in the distribution of grain orientations as well as grain sizes, often leading to uniform or restricted crystallographic orientations or textures. Surface and interface energy minimization and strain energy minimization can lead to development of different textures, depending on which is dominant. The final texture resulting from grain growth depends on the film thickness, the deposition temperature, the grain growth temperature, the thermal expansion coefficients of the film and substrate, and the mechanical properties of the film, as well as other factors.
Epitaxy and Crystallographic Texture of Thin Films for Magnetic Recording
Authors: Laughlin David E. , Feng Y.C. , Lee Li-Lien , Wong B.
Published: April 2011

Thin films for magnetic recording are usually deposited on metallic Cr underlayers to control their crystallographic texture and other microstructural features such as grain size and crystal perfection. In this paper, the mechanisms involved in the production of thin films (both underlayers and magnetic layers) with specific crystallographic textures is reviewed and discussed. We first present an overview of a model for the development of the initial crystallographic texture of films grown on amorphous substrates. The textures that various films develop during growth are next discussed followed by a review of the role of epitaxy of Co-alloy films on Cr with underlayers and interlayers. The control of grain size of the magnetic film is also discussed in light of the underlayer grain size. Finally, the role of epitaxy on crystalline perfection and subgrain structure is discussed.
Preparation of PZT Thin Films by ECR PECVD
Authors: Kim J. W. , Kim S. T. , Chung S. W. , Shin J. S. , No K. S. , Wee D. M. , Lee W. J.
Published: April 2011

Lead zirconate titanite (PZT) thin films have been prepared on Pt/Ti/SiO2/Si and Pt/Ta/Si2/Si substrates by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) at low temperatures using metal-organic (MO) sources. One of the advantages of this method is the easy control of the cation concentrations in the PZT films through the adjustment of the flow rates of each MO sources. The film compositional ratio Ti/Zr was found to be linearly proportional to the flow rate ratio of the input Ti and Zr MO sources. The Pb/(Zr+Ti) ratio was not so much affected by the Ti source flow rate but was inversely proportional to the Zr source flow rate. Pb concentration in the deposited PZT films increased with increasing Ti source flow rate and with decreasing substrate temperature. Perovskite single phase PZT films were successfully fabricated at low temperatures below 500 °C. The perovskite structure was obtained when the Pb/(Zr+Ti) ratio in the deposited film was close to 1.
Internal Stress Change of Phosphorus-Doped Amorphous Silicon Thin Films During Crystallization
Authors: Miura Hideo , Nishimura Asao
Published: April 2011

Internal stress change of phosphorus-doped silicon thin films during crystallization is measured by detecting substrate curvature change using a scanning laser microscope. The films are deposited in an amorphous phase by chemical vapor deposition using Si2H6 gas. The deposited films have compressive stress of about 200 MPa. The internal stress changes significantly to a tensile stress of about 800 MPa at about 600 °C due to shrinkage of the films during crystallization. The high tensile stress can be relaxed by annealing above 800 °C. The phosphorus doping changes the crystallization process of the films and their final residual stress.