bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Recombination Measurements in HgCdTe by Optical Modulation Frequency Response
Authors: Mroczkowski J. A. , Lesondak E. , Resler D.
Published: March 2011

The frequency response in the modulation of the excess electron concentration, produced by a modulated photogenerating pump beam, is used to determine bulk life-time and the surface or interface recombination velocity. The depth-wise integrated excess electron concentration is contactlessly monitored by the proportional absorption/ transmission modulation of a second probe beam. Using this approach over the 20 kHz to 3 MHz frequency range recombination velocities up to 104 cm/sec have been measured in n-type epitaxial HgCdTe films.
Liquid Phase Epitaxy of Hg1−xCdxTe from Te Solutions: A Route to IR Detector Structures
Authors: Gertner E. R.
Published: March 2011

The intrinsic semiconductor mercury cadmium telluride (Hg1−xCdxTe), a solid solution of HgTe and CdTe, has assumed an ever increasing role in the fabrication of infrared (IR) detectors because its energy gap (0-1.5 eV) can be tailored to match the specific needs of IR detection and fiber optic systems. In photovoltaic focal plane array (FPA) applications, low power consumption, as well as excellent sensitivity at elevated temperatures, have made Hg1−xCdxTe the material of choice for both the midwave IR (MWIR) and longwave IR (LWIR) region.
Orientation Effects on the Heteroepitaxial Growth of CdxHg1−xTe on to CdTe and GaAs
Authors: Giess J , Gough J S , Irvine S J C , Mullin J B , Blackmore G W
Published: March 2011

For MOVPE growth of CdTe on to (100) GaAs the orientation of the epitaxial layer is dependent on a combination of the growth conditions and substrate treatment prior to growth, (100) being the preferred orientation. (111) oriented CdTe layers can be grown on to (111) GaAs substrates. The effect of orientation on the choice of buffer composition, electrical properties and the extent of Ga diffusion from the substrate is discussed. Epitaxial CMT layers grown on to suitably buffered GaAs substrates are compared to similar layers grown on to CdTe substrates.
Modeling of HgCdTe Heterojunction Devices
Authors: Zanio Ken , Hay Ken
Published: March 2011

A model for generating the composition and doping profiles from growth and diffusion parameters was developed for heterostructure devices. Poisson's equation was applied to these structures to predict barriers in the conduction band to minority carrier flow for long wavelength HgCdTe infrared detectors prepared by LPE techniques. Spectral response and quantum efficiency measurements illustrate the presence of these barriers and support the use of this model in predicting barrier formation.
HgTe-CdTe Superlattices Grown by Photo-MOCVD
Authors: Ahlgren William L. , James J. B. , Ruth R. P. , Patten E. A. , Staudenmann J.-L.
Published: March 2011

HgTe-CdTe superlattices have been grown, for the first time, by photoassisted MOCVD. The substrate temperature was 182°C. Superlattices were obtained despite low growth rates requiring long growth times (∼10 hours). Interdiffusion during growth may be slowed down by growing under saturated Hg vapor to minimize cation-vacancy formation. The nominal superlattice structures were 70Å HgTe-30Å CdTe, 40Å HgTe-40Å CdTe, and similar. Actual superlattice structures were verified by cross-sectional TEM and diffractometer x-ray diffraction patterns. The x-ray diffraction patterns showed satellite peaks up to third order. The actual structures had HgTe layers ∼20% thicker than the nominal (target) values. A grid-like array of dislocations at the substrate-epilayer interface, suggesting operation of a dislocation-blocking mechanism, was observed. Deficiencies in the superlattice growths include a low growth rate, nonuniform layers, high dislocation density (∼108 cm−2 in best layers), and high n-type carrier concentration (∼1018 cm−3 with mobilities up to 3.5 × 104 cm2 V−1 s−1 in the best layer) which may reflect the presence of donor impurities in the material.
Shallow Junction Formation by the Redistribution of Species Implanted into Cobalt Silicide
Authors: Ditchek Brian M. , Marvin Tabasky Marvin Tabasky , Bulat Emel S.
Published: March 2011

Interest in CoSi2 as a metallization for very large scale integrated circuits (VLSI) has grown rapidly since the recent demonstration of a simple self-aligned process performed by rapid thermal annealing.1-4 Using a rapid thermal anneal (RTA) to directly silicide Co on Si yields smooth low-sheet-resistance films with little or no lateral diffusion and low contact resistance. In addition, it has been shown that rapid thermal annealing can result in reasonable quality epitaxial CoSi2 on (111) Si wafers.5 An important advantage of CoSi2 over the more commonly used TiSi2 metallization is the relative simplicity of its self-aligned silicidation process. Due to the low reactivity of Co with SiO2, a simple two-step self-alignment process is possible instead of the three-step process necessary with TiSi2.6 The primary disadvantage of CoSi2 is the amount of Si consumed for equal silicide sheet resistance. For example, to yield a silicide sheet resistance of 1.5 1/LD, Van den Hove 4 finds that compared to the TiSi, process, the CoSi, process would consume an additional 24 nm of Si. (This disadvantage can be minimized if very shallow junctions can be formed under the CoSi2.)
Limited Reaction Processing: Silicon and III–V Materials
Authors: Gibbons James F. , Reynolds S. , Gronet C. , Vook D. , King C. , Opyd W. , Wilson S. , Nauka C. , Reid G. , Hull R.
Published: March 2011

Limited Reaction Processing (LRP) is a new technique which combines Rapid Thermal Processing (RTP) and Chemical Vapor Deposition (CVD). The added temperature control provided in rapid thermal processing enables the use of substrate temperature as a reaction switch. In addition, rapid thermal technology has been shown to provide other advantages for chemical vapor deposition of Si and III–V materials. Results are presented for group IV materials including epitaxial Si, SiGe alloys, SiO2 , and polysilicon. MOSFETs have been demonstrated and sensitive tests of interface quality are presented, paving the way for future bipolar transistor fabrication. III–V materials such as GaAs, AlGaAs, InGaAs have been grown. GaAs electron mobilities are the best reported for material grown using trimethylarsenic. As-ambient rapid thermal anneals of GaAs have also been performed.
Diffusion of Zn into Gaas 0.6 P0.4:Te From Zn-Doped Oxide Films By Rapid Thermal Processing
Authors: Usami A. , Tokuda Y. , Shiraki H. , Ueda H. , Wada T. , Kan H. , Murakami T.
Published: March 2011

Rapid thermal processing using halogen lamps was applied to the diffusion of Zn into GaAs0.6 P0.4:Te from Zn-doped oxide films. The Zn diffusion coefficient of the rapid thermal diffused (RTD) samples at 800°C for 6 s was about two orders of magnitude higher than that of the conventional furnace diffused samples at 800°C for 60 min. The enhanced diffusion of Zn by RTD may be ascribed to the stress field due to the difference in the thermal expansion coefficient between the doped oxide films and GaAs0.6P0.4 materials, and due to the temperature gradient in GaAs0.6P0 4 materials. The Zn diffusion coefficient at Zn concentration of 1.0 × l018 cm−3 was 3.6 × 10−11, 3.1 × 10−11 and 5.0 × 10−12 cm2 /s for the RTD samples at 950°C for 6 s from Zn-, (Zn,Ga)- and (Zn,P)-doped oxide films, respectively. This suggests that Zn diffusibility was controlled by the P in the doped oxide films.
Si implants into Preamorphised GaAs
Authors: Gwilliam R. , Deol R.S. , Blunt R. , Sealy B.J.
Published: March 2011

Dual implants of (P+ + Si+) through thin Si3N4, layers have been studied. The phosphorus dose has a marked effect on the electrical properties of 6 × 1012 Si+ cm−2. Optimum electrical activation occurred at a phosphorus dose well below that required to produce an amorphous layer and depended on whether a furnace or a rapid thermal anneal was performed. Good control over the tail of the electron concentration profile was obtained for doses of phosphorus in the range 6 × 1012 to 1 × 1014 ions cm−2.
Carrier and Atomic Distributions in Si Implanted and Rapid Thermally Annealed InP ; Influence of Dual Implants of As or P
Authors: DUIIAMEL Nicole , DESCOUTS Brigitte , KRAUZ Philippe , RAO Krishna , DANGLA Jean , HENOC Pierre
Published: March 2011

Rapid thermal anneal (R.T.A.) by halogen lamps has been carried out to activate Si29 implants in semi-insulating InP substrates with the aim of realizing good contact areas at low depth (0.1 μm). To better understand the electrical behaviour of Si observed in these conditions, and to try to increase the electrical activity we performed dual implantations (As + Si or P + Si). The crystallographic disorder remaining after anneal and its influence on the electrical properties are discussed. The uniformity of activation has been evaluated by Hall effect and specific contact resistivity cartographies both for mono-implantations and for dual implantations.
Epitaxial Alignment of as Implanted Polysilicon Emitters
Authors: Hoyt J.L. , Crabbé E.F. , Gibbons J.F. , Pease R.F.W.
Published: March 2011

We demonstrate a clear advantage for high-temperature, short time annealing to induce intentional, complete epitaxial alignment of arsenic implanted, 0.5 μm-thick polysilicon films on (100) silicon, while minimizing arsenic outdiffusion into the substrate. Using MeV ion channeling and cross-sectional electron microscopy, epitaxial alignment was studied in the 1050-1150 °C temperature range, for arsenic doping concentrations between 1 and 10 × 1020 cm−3. The alignment efficiency increases dramatically with chemical arsenic concentration in this range. An arsenic concentration of 1020 cm−3 yields alignment behavior which proceeds from the polysilicon/single-crystal interface. Between 1 and 5 × 1020 cm×3, the random grain growth can exceed the rate of alignment, and large grain, highly oriented polycrystalline films can result from the RTA. For 0.5 μm-thick polysilicon films with an average doping of 1021 cm×3, the rate of achievement of a high degree of epitaxial alignment exceeds the rate of arsenic penetration into the substrate at temperatures ≥ 1150 °C.

Bipolar transistors with 0.5 μm-thick emitter contacts and polysilicon dopings of 5 and 10 × 1020 cm×3 show less variation in base current when subjected to RTA (T ≥ 1100 °C) compared to devices annealed in a furnace in the 900 to 1000 °C range, while retaining the advantage over metal contacts.
A Study of Grain Growth in Ion Irradiated Co-Cr Alloy Films
Authors: Li J. , Liu B. X. , Li H. D.
Published: March 2011

Experiments concerning the behavior of grain size in Co80Cr20 alloy thin films upon ion irradiation were conducted. The alloy films of 80 nm thick were prepared by magnetron sputtering on cleaved NaCl crystal substrates, and then irradiated by 300 keV argon or xenon ions to a wide range of doses. The irradiated samples, before and after annealing, were examined by transmission electron microscope (TEM). It was found that the initial grain size with the dimension of 20 nm remained unchanged when the dose was less than 1×1016Ar/cm2, but rapidly reduced to the scale of 5 nm at a dose of 5×1016Ar/cm2. It is thought that this is due to a polymorphic transformation of an HCP to a BCC structure in the alloy films. After 30 min. anneals at 200° C, it was observed that the grain growth rate was a function of ion dose, and that there exists a critical fluence yielding a maximum grain growth rate. The possible mechanisms for the observations in this study are discussed.
Variable Angle Spectroscopic Ellipsometry (VASE) for the Study of Ion-Beam and Growth-Modified Solids
Authors: Woollam John A. , Snyder Paul G. , Rost M. C.
Published: March 2011

In the most commonly used form of ellipsometry, a monochromatic collimated linearly polarized light beam is directed at an angle φ to the normal of a sample under study. The specularly reflected beam is, in general, elliptically polarized, and the state of polarization is analyzed using a second polarizer and photodetector.1 Figure 1 shows a schematic of the rotating analyzer automated spectroscopic ellipsometer used at the University of Nebraska. The angle of incidence can be set over a wide range of angles, with a precision and repeatability of ±0.01 angular degrees. A computer controls the monochromator, the azimuth of a stepper motor driven polarizer, a shutter, and the digitization of the detector signal. There are several other schemes used for acquiring ellipsometric data, and these are discussed in several sources.
Ion-Beam-Induced Plastic Deformation of Amorphous Materials
Authors: Klaumünzer S. , Ming-Dong Hou , Schumacher G. , Chang-Lin Li
Published: March 2011

At temperatures far below the glass transition temperature metallic glasses undergo plastic deformation during irradiation with a beam of fast heavy ions at energies at which electronic stopping is the dominant deceleration mechanism. This plastic deformation causes irreversible anisotropic changes in sample dimensions. Various (Fe,Co,Ni)∼8O(B,Si)∼20 glasses and the crystalline alloys Ni80Cr20 and Fe70Cr25A15 are examin? 9 for their susceptibility to this effect by irradiation below 50 K with 129Xe ions at 2.8 MeV/u. The data suggest that the excess free volume of an amorphous material is an essential parameter for the magnitude of ion-beam-induced plastic deformation.
Ion Mixing of Near-Noble Transition Metal Films on Evaporated and Large-Grained Aluminum Substrates
Authors: Ma E. , Zhao X.-A. , Nicolet M-A.
Published: March 2011

Ion mixing experiments using Xe ions at temperatures ranging from 77K to about 450K were conducted on Al/Ni and Al/Pt couples. Evaporated polycrystalline Al films and large-grained Al crystals were used as substrates. Xenon irradiation of Al/Pt bilayers achieves considerable intermixing and a temperature dependence is observed. Only moderate interfacial mixing with little temperature dependence is observed in Al/Ni bilayers. The mixing efficiency of Al/Ni is consistent with the phenomenological model of thermal spike mixing, and so is the absence of a pronounced temperature dependence below 450K. No significant difference is noted in ion mixing of evaporated and large-grained Al substrates. In contrast to ion mixing, Al/Pt and Al/Ni samples behave similarly upon thermal annealing and form well-defined compounds. The results are also compared with Si/metal systems, where silicides can be formed readily by low temperature thermal annealing as well as by ion mixing of bilayer samples.
Cross-sectional TEM and corrosion studies of Al and N implanted copper
Authors: Gerritsen E. , Ligthart H. J. , Deenen T. E. G.
Published: March 2011

Poly- and single crystalline copper was implanted with aluminium and nitrogen at doses ranging from 1016 to 5 × 1017 at/cm2 and energies of 170 keV. The corrosion resistance of the implanted surfaces was tested by exposure to an H25-containing atmosphere. The amount of copper sulphide formed was measured by chrono potentiometric reduction. The amount of corrosion products was markedly reduced (up to a factor 50) by high dose implantations of aluminium. The microstructure of the implanted copper was examined by Transmission Electron Microscopy of cross-sectioned specimens. A deep damage layer far exceeding the ion range was observed. XTEM-pictures of aluminium implanted copper single crystals of various orientations suggest a channeling mechanism for this deep damage layer. In situ annealing of the specimens in the TEM showed that most of the implantation damage is removed at 600°C except for an array of dislocations at the end of the damage range.
X-Ray Measurements of Lattice Strain in Doped Epitaxial Silicon
Authors: Pogany A. P. , Preuss T. E.
Published: March 2011

(100) silicon amorphized by antimony ion implantation was epitaxially regrown by either furnace or pulsed laser annealing. Rocking curves were measured on a double-crystal X-ray diffractometer, and compared with calculations based on a one-dimensional strain profile. For laser annealed samples the strain profile followed that of the antimony (redistributed by surface melting), with a proportionality constant given by the Pauling covalent radius ratio. For furnace annealed samples however the strain was found to be deeper, but of smaller peak magnitude, than that expected from the antimony distribution. This is attributed to formation and movement of defects acting to relax lattice strain. Other X-ray strain measurements on epitaxial silicon containing other dòpants are briefly reviewed.
Implanted Dopant-Defect Interactons in GaAs
Authors: Pearton S. J. , Williams J. S. , Short K. T. , Johnson S. T. , Gibson J. M. , Jacobson D. C. , Poate J. M. , Boerma D. O.
Published: March 2011

The implantation temperature dependence of dopant solubility and electrical activity was investigated for Sn, Cd and Te ions in GaAs. Implantation doses of 5×1012 – 5×1015 cm−2 were performed in the temperature range from LN2 to 400°C, followed by rapid thermal annealing (950°C) or furnace annealing between 650°C and 850°C. Solubilities above 1020 cm−3 were obtained for all of the species, with a peak value of 2.5×1021 cm−3 for Te after 850°C furnace annealing. However essentially no correlation existed between dopant solubility and electrical activity or between electrical activity and the high density of defects remaining after many of the annealing cycles. This emphases the role of fine scale, point defect complexes in controlling the electrical activity of implanted dopants in GaAs.
Epitaxy for Weakly Interacting Systems of Large Misfit
Authors: Dregia S. A. , Wynblatt P. , Bauer C. L.
Published: March 2011

A simple but general model is developed which describes the elastic relaxations in a misfitting epitaxial thin film on a rigid substrate. The film is treated as a two-dimensional, elastically anisotropic solid with an arbitrary orientation relationship to the underlying substrate. The periodic elastic displacement field, the misfit energy density, and the elastic energy density of relaxation are derived for relatively weak, periodic film-substrate interactions of a generalized form. The model is tested for a misfitting Ni-(111) monolayer in contact with a rigid Ag-(111) substrate, using computer simulations with the embedded atom method. The predicted displacement field has symmetry 3m and has a magnitude which is in close agreement with that obtained by a fully numerical solution. The dependence of the extent of relaxations on the form of the film-substrate interaction is discussed for the special case of unidirectional misfit.
In-Situ Studies of the MBE Growth of CoSi2 on Si (111) in a UHV Transmission Electron Microscope
Authors: Gibson J. M. , Batstone J. L. , Tung R. T.
Published: March 2011

In-situ observations of the growth of CoSi2 films by Co deposition in an ultrahigh vacuum transmission electron microscope are described. Results include the observation of intermediate epitaxial phases (both hexagonally distorted Co2Si and CoSi) and the observation that pinholes nucleate in CoSi2 films after growth in a metastable layer mode.
In-Situ Ellipsometry and Light Scattering Studies of Substrate Cleaning and Initial Layer Deposition in Low Temperature CVD of Crystalline Si
Authors: Pickering C. , Robbins D. J. , Young I. M. , Glasper J. L. , Johnson M. , Jones R.
Published: March 2011

The first in-situ observations of initial stages of growth during Si vapour-phase homoepitaxy are reported, using the simultaneous measurement of dual-wavelength ellipsometry (364/488nm) and diffuse light scattering (488nm). Effective medium modelling shows that initial growth is nonuniform with pits present in the first 50–200Å of growth which rapidly fill in as growth proceeds. The sizes of the ellipsometric and scattering discontinuities are dependent on the extent of pre-growth roughening associated with oxide removal and finite wavelength effects become important for growth on roughened substrates.
Bonding at the CaF2-on-Si(111) Interface
Authors: Olmsteadt Marjorie A. , Bringans R. D. , Uhrberg R. I. G. , Bachrach R. Z.
Published: March 2011

The bonding at the interface between CaF2 and Si(111) has been investigated using core-level photoemission spectroscopy. The results are discussed in terms of various structural models of the interface. The stable interface has a depletion of fluorine from the interface resulting in strong Si - Ca bonding.
Reactions in OMVPE Growth of InP
Authors: Stringfellow G. B. , Buchan N. I. , Larsen C. A.
Published: March 2011

Organometallic vapor phase epitaxy (OMVPE) has achieved remarkable recent success, becoming the most promising technique for the ultimate production of III/V materials and device structures. Unfortunately, our understanding of the growth process remains primitive. In this paper we report a new technique for tracing the reactions by conducting the epitaxial growth in a D2 ambient using a time-of-flight mass spectrometer to analyze the product molecules. The pyrolysis reactions were studied for PH3, both alone and in the presence of trimethylindium (TMIn), and for TMIn alone and in the presence of PH3. For the reactants alone, the PH3 pyrolysis is completely heterogeneous at the InP surface, while TMIn pyrolyzes homogeneously in the gas phase. For TMIn and PH3 together, the reaction mechanism is entirely different; the pyrolysis temperatures for both PH3 and TMIn are lowered. Since the reaction produces only CH4 molecules, with a complete absence of CH3D at high ratios of PH3 to TMIn, we hypothesize that InP growth is initiated by the direct interaction of TMIn and PH3 molecules, either in the vapor phase at normal growth temperatures or at the InP surface at temperatures as low as 250°C.
Charge Transfer and Surface Reaction in Silicon Vapor Phase Epitaxial Growth
Authors: Ishitani A. , Takada T. , Ohshita Y. , Tanigaki K.
Published: March 2011

Silicon vapor phase epitaxial growth with SiH2Cl2 is theoretically studied. The optimized geometries and total energigs of the species, generated from SiH2Cl2, are calculated by using ab initio molecular orbital method. As the intgraction between silicon surface and SiCl2 the charge transfer is considered. Based on the computational result that SiCl2 - has the lower total energy than SiCl2, a new adsorption mechanism, named, charge transfer adsorption, is p~oposed. By using this charge transfer adsorption followed by the surface reaction at the hollow bridge site, the epitaxial growths on the silicon (001), (111), and (110) surfaces are discussed.
Photoconductivity Decay in Amorphous Semiconductors
Authors: Pickin William , Mendoza Doroteo , Alonso Juan Carlos
Published: March 2011

Based on modifications of the standard multiple trapping approach we present a theory of photoconductivity decay from the steady state in which explicit account is taken of the minority carrier behaviour. We use this to develop a physical understanding of the decay process. We obtain the intensity dependence of the decay time and compare it with experimental results for hydrogenated amorphous silicon.
Amorphous Silicon Deposition Diagnostics Using Coherent Anti-Stokes Raman Spectroscopy
Authors: Shing Y. H. , Perry J. W. , Coulter D. R. , Radhakrishnan G.
Published: March 2011

In situ process diagnostics using coherent anti-Stokes Raman spectroscopy (CARS) have been performed under state-of-the-art a-Si:H film deposition conditions in a reactor designed for a-Si:H solar cell fabrication. The silane plasma of device-quality a-Si:H film depositions was monitored by measuring the silane ν1 band CARS spectrum to determine the depletion induced by the RF glow discharge. The silane depletion is linearly dependent on the RF power in the region of 4 to 12 W with a slope of O.5%/mWcm−2. The depletion is also dependent on the SiH4 flow rate starting with a 50% depletion at a low flow rate of 5.6 sccm and asymptotically approaching an 8% depletion at a high flow rate of 80 sccm. The a-Si:H film deposition rate is systematically measured as a function of the flow rate and the RF power. Linear correlations between the silane depletion and the film deposition rate are observed. The results are discussed in terms of primary electron impact dissociations of silane and the residence time of SiH4 molecule in the glow discharge region.
Deposition of a-SiNx Films by ArF Laser Induced CVD as Diagnosed by Optical Emission Spectroscopy
Authors: Nishikawa S. , Matsuhashi H. , Ishida T. , Ohno S. , Ushio S.
Published: March 2011

Deposition of SiNx films by ArF laser induced chemical vapor deposition has been investigated. The films exhibit excellent electrical properties; the high breakdown voltage and the low fixed charge are the same as in films deposited by LPCVD, but the BHF etching rate of them is larger by a factor about 4 than that prepared by the plasma CVD. The diffusion length of the radicals contributing to the deposition was estimated from the distribution of the deposition rate as a function of the deposition parameters. The optical emission from the radicals produced by ArF laser irradiation was also studied. Using these results, we discuss the mechanism of the deposition.
IR-Spectroscopy and Electronic Properties of RF Magnetron Sputtered a-SiA:H (A=C,Ge) Films
Authors: Rubel H. , Schröder B.
Published: March 2011

a-S1−xCx:H and a-Si1− Ge :H films are prepared by magnetron sputtering in an argon-hydrogen-methane/germane atmosphere. The hydrogen content of the carbon alloy increases with x, saturating near 40 at% for the maximum C-content (x = 0.88). From a detailed analysis of the infrared absorption modes we conclude that the formation of (CHm)n C/Si-groups (n = 1,2,3, m = 2,3) is responsible for the growth of hy r gen rich and inhomogeneous films. Structural, electrical and optical properties of the films show characteristic changes near an alloy composition of x = 0.5 which indicate the transition to a structure with threefold coordinated carbon. For the germanium alloy system lower DOS and improved photoelectrical properties have been measured for y ≤ 0.01. Decreasing H-content and SiH2 /GeH2 bonding configurations impair the alloy properties for higher y.
Recombination and Electronic Transport in Low-Gap a-Si,Ge:H,F Alloys
Authors: Aljishi S. , Shen D. S. , Chu V. , Smith Z E. , Conde J. P. , Kolodzey J. , Slobodin D. , Wagner S.
Published: March 2011

We have studied the temperature and intensity dependence (130K to 300K) of photo- and dark conductivity in a series of low-gap a-Si,Ge:H,F alloys (Eopt=1.25 to 1.33 eV) prepared under different deposition conditions. Electron time of flight experiments were conducted between 300K and 400K. Results reveal an increase in the slope of the exponential conduction band tail to ∼ 50 meV and a peak in electron trapping states at 0.3 to 0.4 eV below the conduction band edge, leading to a transition from extended to hopping conduction by electrons at slightly below room temperature. The alloys have midgap defect densities in the low 1017 cm−3eV−1 range.
Estimation of Defect State Densities from Bulk Photoelectronic Properties of a-Si,Ge:H Alloys
Authors: Parsons G. N. , Lucovsky G.
Published: March 2011

We have studied the photoelectronic properities of a- Si(x),Ge(1−x):H alloy films and have concluded that there are depletion layers at the film surface and film/oxide interface that effect the determination of bulk quantum effieciencymobility- lifetime (nuT) products. From changes in dark conductivity activation energy with film thickness and the nuT product with wavelength of incident light we have estimated defeci sta:e lensitles. Our best x=0.5 film has an nuT value of 9×10−8 cm2 V−1 andaj defect state density near the Fermi level of approximately 5×10 cm−3 eV−1.
Schottky Barriers on a-Si:H,F/a-Si,Ge:H,F Superlattices
Authors: Chu V. , Conde J. P. , Aljishi S. , Shen D. S. , Smith Z E. , Wagner S.
Published: March 2011

We report measurements of Schottky barrier heights and minority carrier mobilitylifetime products of multilayer structures composed of a-Si:H,F and a-Si,Ge:H,F. These layers are grown by r.f. glow discharge decompostion of SiF4, GeF4, and H2 in the a-Si,Ge:H,F (well) layer and of SiF4 and H2 in the a-Si:H,F (barrier) layer.

Schottky barrier height ΦB of Pt is measured using internal photoemission measurements. The minority carrier mobility-lifetime product (μτ)p is extracted from a fit of the voltage dependence of internal quantum efficiency to the Hecht expression. Both ΦB and (μτ)p are measured as a function of barrier and well thicknesses.
Determination of the Density of Gap States in a-Si:H from Studies of Semiconductor/Oxide Multilayer Films
Authors: Jones R. B. , Moddel G.
Published: March 2011

A method for determining the density of states [N(E)] in the upper half of the energy gap in hydrogenated amorphous silicon (a-Si:H) is proposed and experimental results are simulated. The method involves the growth and measurement of the planar conductivity in multilayer films in which each layer is separated by a thermally grown oxide. Band-bending occurs at each interface throughout the film thickness. The conductivity parallel to the layers in the films is a function of the band-bending, which in turn depends on N(E), in the energy range through which the Fermi level is shifted. Computer simulations of the oxide-induced band-bending have been used to generate curves of the conductivity as a function of layer-thickness for various N(E). By matching experimental results with the simulation curves, the N(E) may be deduced. The simulations have also been used to show the difference between the bulk conductivity activation energy and effective activation energy which is measured in films influenced by a surface oxide.
a-Si MOS Fet with Native-Oxide Gate Grown by Normal-Pressure and Low-Temperature Thermal-Oxidation Method
Authors: Zhang Hong-Yong , Matsumura Masakiyo
Published: March 2011

Native silicon-dioxide film has been grown thermally under normalpressure and low-temperature conditions, and applied to a gate insulator of amorphous-silicon thin-film transistors. Th highest field-effect mobility under room-temperature conditions was 0.7cm2/Vs. Temperature dependence of the transistor characteristics has also been studied. The transistor has been operated in a wide temperature range from -196 °C to more than 200°C with satisfactorily stable manner. Characteristic temperature of the localized state density distribution has been estimated to be about 20° C.
Physics of High Efficiency Multijunction Solar Cells
Authors: Yang Jeffrey , Ross Robert , Mohr Ralph , Fournier Jeffrey P.
Published: March 2011

We have shown that high efficiency solar cells can be obtained by incorporating materials of different band gaps in a multijunction configuration. This configuration gives rise to high efficiency due to spectrum splitting as well as superior stability due to thin top cells.

We have fabricated multijunction solar cells and acheived a 13% conversion efficiency using 1.7eV a-Si:F:H and 1.5 eV a-Si:Ge:F:H materials in a three-cell triple configuration. This device was deposited onto a stainless steel substrate coated with a back reflector; it also incorporates a microcrystalline p+ layer.

The physical properties of each of the solar cell layers and their role in the device physics of a high efficiency solar cell will be described.
“Stable” Defects as, Metastable Defects in a-Si:H
Authors: Redfield David
Published: March 2011

An expanded kinetic description of formation and anneal of metastable defects (MSDs) in a-Si:H shows that (1)the apparently “stable” defects are just a statistical subset of the total density of potential MSD sites; (2)the temperature dependence of the saturation density of MSDs has three distinct regions that have not been recognized; (3)the effects of doping in increasing both the density of “stable” defects and the sensitivity to light are readily explained by an increase in the density of total potential defect sites, not just defects; (4)the defects in good undoped material are chemical in origin, not intrinsic to the disordered state of the material.
Changes of IR Vibrational Absorption by Light Soaking in Hydrogenated Amorphous Silicon
Authors: Jang Jin , Park Seung Chul , Lee Chang Geun , Kim Sung Chul , Lee Choochon , Yoon Jung Kee
Published: March 2011

Light-induced changes in vibrational absorption of SiHn have been studied for a-Si:H films. The stretching mode absorption near 2000 cm−1 decreases after light exposure. The magnitude of the change increases as the substrate temperature is lowered, and little change is observed for a-Si:H films deposited above 200°C. From the changes both for the peak and the spectrum, it is suggested that the hydrogen in the bulk diffuses to the microvoids, where it can combine to form H2 in low substrate temperature sample. The B-H modes increase after light soaking, Which is related with the increase in doping efficiency of boron, which is confirmed from the conductivity change with time during illumination.
Light-Induced Degradation and Annealing Behaviour of Amorphous Silicon: A Comparison of Films and Devices
Authors: Bennett M. S. , Wiedeman S. , Rajan K. , Smoot M.
Published: March 2011

The kinetics of the Staebler-Wronski effect in a-Si:H p-i-n solar cells are well known [1]. We report measurements of the kinetics of light-induced degradation and annealing of a-Si films in which we have monitored the changes in subgap absorption by means of photothermal deflection spectroscopy (PDS). The kinetics of films and cells are found to be very similar, suggesting that cell degradation is largely a material, as opposed to a device effect.
A High Speed High Resolution Contact Line Imager Using Amorphous Silicon Alloy Pin Diodes
Authors: Swartz L. , Kitamura K. , Vijan M. , McGill J. , Cannella V. , Yaniv Z.
Published: March 2011

We report the development of a very high speed high resolution contact line imager using amorphous silicon alloy PIN diodes both as photosensing elements and as isolation diodes in the multiplexing scheme. High speed is achieved by reading the integrated photocurrent in 8μsec and using current integration times less than Imsec. For 200 dots/inch, the scan speed at an illumination of 5×10−4W/cm2 is over 1000 lines/sec. This allows the reading of an A4 (8½″×11″) page in less than 2.0 sec. At this light level, the signal to noise ratio is greater than 40dB. The photosensor array can be used in the true direct contact mode and the multiplexed addressing scheme gives a substantial reduction in the number of peripheral IC chips necessary for operation.
Capacitance Studies of Ion-Implanted N-Type Hydrogenatfd Amdrphous Silicon
Authors: Michelson C. E. , Cohen J. D. , Harbison J. P.
Published: March 2011

The effect of the implantation of oxygen ions on the density of states in the mobility gap of n type hydrogenated amorphous silicon (a-Si:H) is studied using drive-level capacitance profiling, deep-level transient spectroscopy( DLTS), and transient voltage-pulse photocapacitance. After implantation, we observe a broadening of both the conduction and valence band tails and an increase in the dangling bond density near midgap, as well as a shift of the Fermi level toward midgap by approximately 100 meV in two out of the throe films studied. We also observed the addition of a distinct defect band at approximately 0.7 eV below the conduction nd mobility edge in films implanted with oxygen doses greater than 1012 cm−2.
Chemical Vapor Deposited Boron Carbide: Growth by a Vapor-Liquidsolid Process
Authors: Mackinnon Ian D. R. , Smith Katherine L.
Published: March 2011

Detailed analytical electron microscope (AEM) studies of yellow whiskers produced by chemical vapor deposition (CVD)1 show that two basic types of whiskers are produced at low temperatures (between 1200°C and 1400°C) and low boron to carbon gas ratios. Both whisker types show planar microstructures such as twin planes and stacking faults oriented parallel to, or at a rhombohedral angle to, the growth direction. For both whisker types, the presence of droplet-like terminations containing both Si and Ni indicate that the growth process during CVD is via a vapor-liquid-solid (VLS) mechanism.
β-SiC MESFETs
Authors: Kelner G. , Binari S. , Sleger K. , Kong H.
Published: March 2011

A β-SiC MESFET structure with functional DC characteristics has been fabricated and evaluated. The MESFET employs an epitaxial n on p SiC layer grown by chemical vapor deposition on a p-type Si(100) substrate. Modulation of the n-type channel current is achieved with a Au Schottky barrier gate. A transconductance of 2.3 mS/mm was obtained using a 5 micron gate length.
Synthetic Diamond, Its Properties and Synthesis
Authors: Yoder Max N.
Published: March 2011

The synthesis of crystalline diamond in the Soviet Union, Japan, and the United States is reviewed. A comparison of the various growth techniques is presented. Hydrogen and its role in the synthesis process has been controversial; a model is presented illustrating its essential, but limited role. Another controversial aspect of diamond synthesis concerns the nature of the carbon bond in the reactant gas and how this influences the resultant crystal; an heuristic model is provided. Non-thermal equilibrium growth techniques are generic to the recent advances in diamond growth; the separation of the process for the disassociation of the reactant gas from that of the “surface cleaning” and the artificial stimulation of the surface migration velocity may be absolutely necessary for defect-free nucleation and growth. While the various properties of diamond have been known long before the advent of artifact diamond, its potential for use in devices has only recently been modelled and calculated; numerical figures of merit are compared with those of other semiconducting materials. Charge carrier velocity profiles of diamond are compared with those of more conventional semiconductors. Strengths and weaknesses accruing from the diamond velocity profile are addressed.
Electronic Structure of Boron and Boron-Rich Borides
Authors: Switendick Alfred C.
Published: March 2011

I have calculated the electronic structure of cubic B12 and B12 P2 using the linear augmented plane wave method. These calculations are selfconsistent and include calculation of the total energy. Within the strict muffin tin approximation (spheres centered only on atomic positionsconstant potential otherwise) these systems are unbound with respect to the atomic constituents. Using interstitial spheres, up to 77% of the unit cell can easily be filled to yield much more reasonable total energies. Although the improvement in the total energy is significant upon including the interstitial spheres, the band structure and densities of states are not significantly changed. Similarly, the real atomic charge distributions (B, P) are little changed, while the interstitial distribution does change to reflect the additional freedom provided by the interstitial spheres. Results including the rhombohedral and icosohedral distortions in both systems are discussed. Gaps are found to open up in the alpha rhombohedral boron and in the B12 P2 systems as are observed experimentally.
Characterization of Plasma-Deposited Amorphous Carbon Films
Authors: Hsu Wen. L. , Foltz G. W. , Greulich F. A. , Mccarty K. F. , Thomas G. J. , Green P. F. , Doyle B. L.
Published: March 2011

Thin carbon films of ˜ 600 Å have been deposited on Si <111> wafers by striking an RF discharge in gas mixtures of hydrogen and methane. The deposition rate increased with increasing methane fraction. The peak rate was ˜ 1 Å/sec at an applied power density of 0.4 W cm−2. The films, with an average density of 2.54 gm cm−3, are amorphous in nature but exhibit broad diffraction maxima corresponding to interatcidc spacings of 2.05Å and 1. 15Å. Measurements of hydrogen concentration in the films showed that the hydrogen at. % [H/(H+C)] increased from 30 to 40% as the hydrogen fraction in the feed gas increased. By using a D2-CH4, we were also able to deduce that hydrogen molecules can be a large source of hydrogen trapped in the films.
Laser/Optical Diagnostic Techniques for Plasma Materials Processing
Authors: Roman Ward C.
Published: March 2011

The application of plasma techniques is emerging as one of the more efficient means of processing materials. Technology transfer of plasma systems, both thermal and nonequilibrium, however, is severely limited by a lack of understanding of the basic mechanisms involved which govern the plasma processes used in many applications including advanced coatings. The aspects of plasma gas temperature, and species concentration and distribution (molecular, atomic, excited) in the gas phase and associated synergistic effects are fragmentary and unclear. Laser/optical diagnostic techniques represent a critical starting point for providing this needed information; they are in-situ, non-intrusive,species and quantum level specific and give excellent spatial and temporal resolution. A survey of Laser/optical diagnostic techniques applicable to plasma materials processing needs is presented. Some examples of the use of different techniques are also given.
An Experimental Method for Species Concentration Measurements in a Welding ARC Using Laser-Induced Fluorescence
Authors: Snyder S. C. , Shaw C. B. , Shull C. L.
Published: March 2011

An experimental method using laser-induced fluorescence (LIF) to determine the distribution of neutral manganese in a gas tungsten welding arc is described. The theoretical consideration and experimental difficulties encountered when extending LIF techniques from flames to thermal plasmas are discussed, and preliminary results are presented.
Plasma Chemical Aspects of Magnetron Ion Etching with CF4/O2 and CF4/H2
Authors: Bright A. A. , Kaushik S. , Oehrlein G. S.
Published: March 2011

Magnetron plasmas are of great current interest for semiconductor manufacturing applications because of their high ion density and low operating pressure. We have studied the properties of a magnetron ion etching system using CF4, CF4/O2, and CF4/H2 with respect to the plasma chemistry and the interaction of the plasma with the etched substrate. The higher dissociation and ionization rates lead to significant changes in the species present in the plasma as compared to a conventional reactive ion etching (RIE) plasma. The F atom concentration in a CF4 magnetron plasma is much higher than in a RIE plasma. The addition of O2 leads to only a small further enhancement and produces a decrease in the Si etch rate. Addition of H2 suppresses the F atom concentration slightly, produces very little C-F polymer, and does not lead to highly selective etching of SiO2 over Si. The highly dissociated species in the magnetron plasma produce less C-F polymer, both on the wafer and on the chamber walls, relative to RIE.
A New Method for Real-Time Plasma Etch Process Control: Correlation of Contact Resistance with Nondestructive Modulated Reflectance
Authors: Malazgirt Alp , Smith W. Lee
Published: March 2011

We have established a correlation between contact resistance, measured on VLSI MOS integrated circuits at final electrical test, with thermal wave modulated reflectance signal measured just after the metal contact hole etch process. This correlation exists because etching past the time that a particular contact hole is cleared of oxide (i.e., overetching) causes (a) a thinning of the underlying shallow ion-implanted low-resistivity silicon layer with a resulting increase in the contact resistance, and (b) damage to the silicon. Damape was measured on the actual product wafers with the thermal wave modulated reflectance method employing low-power laser beams in a noncontact, nondestructive manner. Hence, the thermal wave measurements of damage make it possible to monitor the etch processing on the product wafers.

Our results show monotonic increases in both the damage (mod. reflec. from 30 to 260 units) and contact resistance (from 40 to 180 ohms/contact) with overetch time up to 1.5 min., at which point polymer deposition alters the dependence by screening the silicon surface. We show results obtained for three categories of VLSI devices (SRAM, PROM, FIFO), and report on the advantages and limitations of this new method for realtime plasma etch inspection.
The Influence of Magnetic Fields on the Properties of Amorphous Carbon Prepared by Plasma Deposition
Authors: Jarman R. H. , Howe A. T.
Published: March 2011

Amorphous carbon films exhibit a wide range of optical, electrical and mechanical properties which make them candidates for a number of applications such as protective coatings and insulators in electronic devices. We describe the effects of a magnetic field applied at the powered electrode in a capacitively coupled rf discharge on the optical and electrical properties of amorphous carbon films deposited on substrates mounted on both electrodes. In the case of substrates placed on the powered electrode, the film properties appear to be very sensitive to the magnetic field strength. At the highest magnetic field, the deposition rates are very much higher than those obtained in the absence of a magnetic field. The optical gap varies from 1.1 eV to 2.7 eV depending on the deposition conditions. The electrical conductivities of the films are very low and show a complex dependence on the applied electric field.
Bonded Hydrogen in Silicon Oxide Thin Films Deposited By Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Tsu D. V. , Lucovsky G.
Published: March 2011

We have deposited a range of silicon oxides by the Remote Plasma Enhanced CVD method. By varying gas mixtures and/or substrate temperature, it is possible to deposit films that are essentially stoichiometric SiO_, Si-deficient oxides which have OH groups but no SiH and Si-rich oxides which have SiH groups and no OH. This paper addresses three issues : (1) the nature of the infrared vibrations associated with the SiH and SiOH groups; (2) the use of D for H substitutions to study the vibrations in (1); and (3) the chemical origin of the SiOH group in the Si-deficient films.
Materials Synthesis
Authors: Strutt Peter R. , Partridge Julian P.
Published: March 2011

Interesting possibilities exist for the scientific design of materials with optimized properties for a diversity of technological applications. For example, the reduction of severe wear and erosion in critical turbine and engine components requires basic studies of intrinsic strengthening, where loads are uniformly transferred across interphase inter-faces. The acheivement of this requires a developed capability for producing selected morphologies on the (i) macro, (ii) micro, and (iii) nanoscale. This involves using a combination of techniques that include the deposition of one, or more, atomic or molecular species in gaseous environments. Recent discoveries suggest, in fact, that it is feasible to design layers where the chemistry and structure at any depth can be pre-selected. Such a capability offers exciting opportunities for forming ‘graded property’ materials, as required in mechanical component and fiber-optic applications. Here, specific radial distributions of chemical species can be used to achieve optimal properties. Another in-triguing possibility is the formation of composite-structure materials, even on the nanoscale, by simultaneous growth of filaments and matrix, using appropriate precur-sors. Thus, metal and polymer matrices may, in principle, be strengthened by various types of fiber and particle distributions. In this approach the basic concept is the syn-thesis of scientifically designed materials for specific technological applications.