bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral line parameters for the O2 Herzberg I band system
Authors: Cann M. W. P. , Nicholls R. W.
Published: April 2011

Spectral line parameters required for line-by-line spectral syntheses have been calculated for the weak Herzberg I band system of O2. The line locations were calculated with constants from Borrell, Borrell, and Ramsay (Can. J. Phys. 64, 721 (1986)), and agree closely with these authors' measured wave numbers. Line strengths were calculated using formulae given by Lewis and Gibson (Can. J. Phys. 68, 231 (1990).) but empirically modified to concur with the relative strengths measured by Herzberg (Can. J. Phys. 30, 185 (1952).), the only ones found in the literature. Line strengths and line widths are both very uncertain and need to be revised as more information becomes available. Line parameters were calculated for transitions from the ν″ = 0, 1, and 2 vibrational levels; a strength cutoff of 1.0 × 10−40 cm2 cm−1 per molecule was imposed.
A note on the enhancement of J values in optically thick scattering atmospheres
Authors: Kaminski Jacek W. , McConnell John C.
Published: April 2011

In a planetary atmosphere the J value is determined by the angular-averaged radiance, or the average density of photons in an element of volume. The average density may be enhanced by multiple scattering of photons in a conservative, or near-conservative scattering atmosphere. We show that in a conservative semi-infinite medium this enhancement will be a factor of 5, for optical depths greater than about 20 for coherent scattering. We investigate the modification of the J values owing to multiple scattering in an optically thick medium of various optical depths, various single-scattering albedos of the scattering medium, and a range of surface albedos. We have applied the results to the calculation of J values in clouds in the terrestrial atmosphere and in the Rayleigh-scattering atmosphere of Uranus. We note that J values in a realistic atmosphere may be enhanced by as much as a factor of 5 throughout a large fraction of the atmosphere over those calculated without multiple scattering and surface reflection.
The development of wide-angle Michelson interferometers in Canada
Authors: Shepherd G. G. , Gault W.A. , Koehler R. A.
Published: April 2011

The history of wide-angle Michelson interferometers in Canada began in 1961, in Paris. This will culminate with the launch of the WINDII (WIND Imaging Interferometer) instrument in 1991, precisely 30 years later. The intervening developments are reviewed, and possible future directions are described.
A dynamic ionosonde design using pulse coding
Authors: Gao S. , MacDougall J. W.
Published: April 2011

A research ionosonde with capabilities for measuring drifts by the spaced-antenna method was designed and a limited prototype tested. Using a PC for much of the control and data storage functions and a small quantity of external electronics will make the instrument small and inexpensive. In particular, pulse compression techniques using a 13 bit Barker code gives an improvement in signal-to-noise ratio of about 11 dB. This allows the use of a transmitter with peak power less than a kilowatt, which is compatible with solid-state electronics.
High-resolution spectroscopic measurements from the space shuttle: Orbiter glow and atmospheric emissions
Authors: Kendall D. J. W. , Llewellyn E. J. , Gale M. R. , Mende S. B. , Swenson G. R. , Gattinger R. L.
Published: April 2011

The orbiter glow (OGLOW) experiment, flown in 1984 on shuttle mission STS-41G, included observations of spacecraft glow and atmospheric emissions. The instrument consisted of a simple hand-held photographic imager combined with a series of high-resolution interference filters, Fabry–Perot interferometers, and a grating spectrometer. In the case of spacecraft glow, the results are summarized and compared with recent laboratory measurements. For the atmospheric emissions, a detailed analysis of the oxygen atmospheric band is presented to show how the data can be used to infer atomic-oxygen height profiles.
Growth efficiency and distribution coefficient of GaInP–InP epilayers and heterostructures
Authors: Bensaada A. , Cochrane R. W. , Masut R. A.
Published: April 2011

We have prepared GaInP epilayers on InP by low pressure metal-organic vapour-phase epitaxy to explore the structural, electrical, and optical properties of this relatively little-studied combination. In this paper, we focus on the growth process of GaInP by examining both single thick epilayers on InP as well as a number of double barriers of GaInP–InP prepared from two different trimethylindium (TMIn) sources. High-resolution X-ray diffraction (HRXRD) has been used to extract layer compositions and thicknesses and. consequently, the growth rates and efficiencies of the binary and ternary layers. In general, HRXRD indicates completely constrained heterostructures of high quality. Combining the growth parameters with the structural data leads to the determination of the Ga distribution coefficient during growth of the ternary compound that is found to depend strongly on the quality and stability of the TMIn source. Results from two series of epilayer depositions using the two TMIn sources are presented to illustrate the strong connection between the quality of the source material and the growth process of the epilayers.
The effect of implant temperature and beam flux on damage accumulation and Si activation of Si-implanted InP
Authors: Akano U. G. , Mitchell I. V. , Shepherd F. R. , Miner C. J.
Published: April 2011

Ion implantation-induced disorder accumulation in Si-implanted InP crystals and the effect of the disorder accumulation on the subsequent electrical activation of the implanted Si have been studied as functions of the Si dose, flux, and implant temperature. InP crystals with (100) orientation were implanted at 80–423 K with 600 keV Si+ ions at a beam flux of 0.005–1.0 μA cm−2 and to total fluences of between 5 × 1012 and 2 × 1014 Si cm−2. The residual displacement damage following implantation was analyzed by the Rutherford backscattering/channeling technique. Electrical activation of the implanted Si was studied using Hall-effect measurements. The results show that for implant temperatures [Formula: see text] the displaced atom density, Nd. exhibits a power law dependence on J: Nd = αJn, with the value of n dependent on both the total ion dose and implant temperature. At 295 K and Si doses of 1–4 × 1013 cm−2, the value of h varies from 0.23 to 0.15. The transition from the crystalline to amorphous state is influenced significantly by the implant temperature. For implant temperatures [Formula: see text], no amorphous state can be produced in InP for Si doses [Formula: see text] and Si fluxes [Formula: see text]. A combination of low beam flux and elevated temperature implantation may be advantageous for the electrical activation of the implanted Si.
Reduced interface state densities for remote microwave plasma silicon nitride
Authors: Landheer D. , Bardwell J. A. , Sproule I. , Scott-Thomas J. , Kwok W. , Lau W. M.
Published: April 2011

The interface state density and fixed charge density of films of a-Si3N4:H deposited on silicon substrates by remote microwave plasma chemical vapour deposition have been studied as a function of deposition and annealing temperature. Interface state densities (Dit as low as 9 × 1010 cm−2 eV−1 have been obtained for films deposited at 215 °C and annealed for 15 min at 500 °C. The films exhibited positive fixed charge levels (QN/q)> 1013 cm−2, increasing slightly with deposition temperature and decreasing slightly with annealing at temperatures from 500 to 700 °C. Fourier transform infrared spectroscopy and Auger depth profiling were used to study the impurities in the films and at the interface. Metal–insulator–silicon field effect transistors made with these films showed room temperature effective channel hole mobilities of 37 cm2 V−1 s−1.
Si K-edge X-ray absorption fine structure studies of porous silicon
Authors: Sham T. K. , Feng X. H. , Jiang D. T. , Yang B. X. , Xiong J. Z. , Bzowski A. , Houghton D. C. , Bryskiewicz B. , Wang E.
Published: April 2011

X-ray absorption fine structure (XAFS) spectra of porous Si prepared by the anodization of a Si wafer in aqueous HF solution have been obtained with synchrotron radiation. The Si K-edge near-edge X-ray absorption fine structure and extended X-ray absorption fine structures clearly show that porous silicon samples that have been exposed to the ambient environment (untreated) have an oxide layer, while the "clean" (treated) porous Si sample regenerated by HF treatment shows some degradation in its crystallinity. Noticeable differences in the XAFS between porous Si and crystalline Si are noted. The results and implications of this observation and the chemistry leading to the formation of surface oxygen compound are discussed.
Electric and magnetic field induced dimensionality reduction in InGaAs-GaAs superlattices
Authors: Roth Alain , Lugagne-Delpon Emmanuel , Voisin Paul
Published: April 2011

We have measured photoconductivity spectra in a InGaAs/GaAs superlattice subjected to longitudinal electric and magnetic fields. We have observed a clear sharpening of the excitonic features in the spectra as the fields increases. Furthermore, the intensity of excitons involving spatially separated electrons and holes increases with increasing magnetic field relative to that of vertical excitons. These observations can be interpreted with a model that lakes into account exciton wavefunction shrinkage induced by magnetic field. Oblique excitons have a smaller binding energy than vertical excitons and are therefore more sensitive to magnetic localization, which enhances their oscillator strength relative to that of vertical excitons. Strong exciton interactions are also observed, giving rise to level anticrossings.
Interfaces effectives et pentes d'Urbach de multicouches a-Si:H/a-SiNx:H
Authors: Beaudoin M. , Meunier M. , Muschik T. , Schwarz R. , Arsenault C. J. , Beaulieu M. , Grimal O.
Published: April 2011

Optical and structural measurements are presented for glow discharge multilayer structures of hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon nitride (a-SiNx:H). Two sets of samples are presented. For set A, the barrier thickness as well as the number of double layers are kept constant whereas, for set B, samples have both constant composition and total thickness. Small-angle X-ray reflectivity measurements (reflectometry) are analyzed using a theoretical model based on the transfer matrix method. This analysis yields an effective width between 1.5 and 2.0 nm for the interfaces. The increase of the Urbach slope parameter with decreasing well layer thickness is measured by photothermal deflection spectroscopy and by Fourier transform photoacoustic spectroscopy. This dependence is analyzed by taking into account the effective interface thickness and it is studied by using the optical absorption model of Abe and Toyozawa (J. Phys. Soc. Jpn. 50, 2185 (1981)). Both sets of samples show the same behavior, which leads to the conclusion that the Urbach slope increase is due to interface effects.
Mechanical properties of silicon carbide films for X-ray lithography application
Authors: Jean A. , Khakani M. A. El , Chaker M. , Gat E. , Dodier J. , Papadopoullos A. , Lafontaine H. , Pépin H. , Kieffer J. C. , Ravet M. F. , Madouri A. , Bourneix J. , Rousseaux F. , Gujrathi S. C.
Published: April 2011

Hydrogenated amorphous silicon carbide a-SixC1−x:H films of various compositions [Formula: see text] were deposited using a plasma-enhanced chemical vapour deposition technique. The as-deposited films are under high compressive stress (1 GPa). The control of the stress relaxation is an important stage in the X-ray mask technology. The stress of the a-SixC1−x:H films is measured by the wafer bow technique, whereas the resonance frequency and the bulge techniques are used to measure the stress of the a-SixC1−x:H free-standing membranes. These three methods give similar results and it is pointed out that the wafer bow technique can be used with confidence to determine the stress of a-SixC1−x:H films intended to X-ray membrane processing. From the bulge method, the biaxial Young's modulus E/(1–ν) of the a-SixC1−x:H membranes is also deduced. Values of 200 ± 25 GPa are obtained for a-SixC1−x:H films at x = 0.4 and 0.5 film compositions. At x = 0.67, E/(1–ν) is reduced by a factor of about two. The structure and composition of the a-SixC1–x:H films were investigated by means of elastic recoil detection, X-ray diffraction, and Fourier transform infrared absorption techniques. It is shown that the biaxial Young's modulus increases with the Si–C bond density in the film.
Epitaxial tilt of partially relaxed InGaAs layers grown on (100) GaAs substrates
Authors: Maigné P. , Roth A. P. , Desruisseaux C. , Coulas D.
Published: April 2011

The structural properties of partially relaxed InxGa1−xAs layers grown on (100) GaAs substrates have been investigated, using high-resolution X-ray diffraction, in order to better understand the mechanisms responsible for the relaxation of the mismatch strain. From symmetric [400] reflections recorded as functions of the azimuthal angle [Formula: see text], the (100) InGaAs planes are found to be tilted with respect to the (100) GaAs substrate planes. The tilt magnitude is first seen to decrease then to increase with layer thickness. The direction of the tilt changes from [01-1] to [00-1] in the range of thickness investigated. From [422] asymmetric reflections, the average in-plane lattice parameter, the indium composition as well as the percentage of relaxation can be measured. Our values for relaxation are in qualitative agreement with the Dodson and Tsao model of strain relaxation (Appl. Phys. Lett. 51, 1710 (1987)). In addition, our data show an anisotropy in residual strain along <011> directions. This anisotropy increases with the amount of strain relieved and changes the crystal symmetry of the cell from tetragonal to monoclinic. This monoclinic symmetry can be characterized by an angle β that measures the angle between 90° and the inner angles of the new crystallographic cell. As for the anisotropy in residual strain, |3 increases with the amount of strain relieved. Correlations between tilt magnitude and tilt direction with the formation of 60° type dislocations are discussed.
Transmission electron microscopy characterization of In1−xGaxSb on (001) GaAs heteroepitaxial system
Authors: Robertson M. D. , Corbett J. M. , Webb J. B. , Rousina R.
Published: April 2011

Seven In1−xGaxSb [Formula: see text] films grown on a (001) GaAs substrate by metalorganic magnetron sputtering were characterized using cross-sectional transmission electron microscopy techniques. Analysis included high-resolution and diffraction contrast imaging, selected area diffraction, and energy dispersive X-ray methods. The epilayers were not observed to possess significant amounts of large-scale residual strain owing to the lattice mismatch; however, localized strain was apparent under diffraction contrast imaging in some films. High-resolution electron microscope analysis indicated that the interfacial lattice mismatch was accommodated by arrays of 60 and (or) 90° dislocations, the distributions of which were found to obey the Frank–Bilby equation for epitaxial systems. Epilayer tilting was observed in the heteroepitaxial systems that possessed a significant substrate inclination. The magnitude and direction of the film tilt, to a first approximation, appeared to be associated with the particular distribution of 60° dislocations observed at the interface. Also, it was observed that surface roughness of the substrate can lead to grain boundaries in the films. Finally, growth defects, specifically stacking faults and threading dislocations, were present in qualitatively varying degrees in the films studied.
Improving transmission electron microscopy characterization of semiconductors by minimizing sample preparation artifacts
Authors: McCaffrey J. P. , Sproule G. I. , Sargent R.
Published: April 2011

Techniques employed for the preparation of transmission electron microscopy (TEM) samples can introduce artifacts that obscure subtle detail in the materials being studied. Traditional semiconductor sample preparation techniques rely heavily on ion milling, which leaves amorphous layers on ion milled surfaces and some intermixing across interfaces, thus degrading the TEM images of these samples. Experimental results of the extent of this amorphization and intermixing are presented for silicon-based semiconductor samples, and methods to minimize these effects are suggested. These methods include variations in ion milling parameters that reduce the extent of the artifacts, and improvements in the small-angle cleavage technique that eliminate these artifacts completely.
Process optimization for a micromachined silicon nonreverse valve
Authors: Stoev I. , Syrzycki M. , Parameswaran M. , Chapman G. , Rawicz A.
Published: April 2011

The paper targets the development and optimization of technology for a micromachined silicon nonreverse valve, intended for fluid delivering applications in miniature fluidic systems. Several combinations of valve geometries and semiconductor process parameters were investigated, resulting in fabrication of different structures. Two-dimensional simulations were used to optimize the process parameters necessary to obtain V-grooved silicon membranes of specific thicknesses. The mechanical performance of the valve was also tested. Finally, modifications of valve structure for possible integration with a pressure sensor were proposed.
Dépôt par laser de WSix sur du TiN à partir de WF6 et de SiH4
Authors: Desjardins P. , Izquierdo R. , Meunier M.
Published: April 2011

A direct writing system has been developed for the deposition of WSix on TiN from a gas mixture of WF6 and SiH4. An Ar+ (488 nm, 1.5 W) and a diode laser (796 nm, 1.0 W) are used as the photon source. Lines are written at scan speeds of up to 100 μm s−1 from a flowing gas mixture of WF6 and SiH4 diluted in Ar. Deposits of 1.5 to 11 μm wide and 20 to 180 nm thick are obtained at a writing speed of 100 μm s−1 with the Ar+ laser. Lines written using the diode laser are typically 4 to 12 μm wide and 160 to 860 nm thick. The W/Si ratio in the deposit is between 1.5–1.8 for a mixture of 1 sccm WF6 and 3 sccm SiH4 diluted in 50 to 150 sccm Ar.
Numerical study of heat transport in thermally isolated flow-rate microsensors
Authors: Swart N. , Nathan A.
Published: April 2011

The temperature distributions in thermally isolated cantilever based flow-rate microsensors have been numerically calculated for different gas temperatures and gas velocities. In particular, we investigate the efficiency of heat transfer to the flowing gas and corresponding directions of heat flow in the system. The above analysis is based on a solution to the energy equation under appropriate boundary conditions. The equation was discretized using a control volume procedure, based on which an equivalent circuit was devised and subsequently simulated using a circuit simulator such as SPICE.
Wavelength and threshold current variation in inhomogeneously pumped InGaAs/AlGaAs single and double quantum well ridge wave-guide lasers
Authors: McGreer K. A. , Moss D. , Williams R. L. , Dion M. , Landheer D.
Published: April 2011

We investigate the wavelength and threshold current variation with passive wave-guide length in inhomogeneously pumped single and double quantum well InGaAs/AlGaAs strained layer ridge wave-guide lasers. We observe a linear and extremely low increase in threshold current with unpumped length, both for single and double quantum well lasers. A large red shift in the lasing wavelength as the unpumped length is increased is also observed. We present a model, based on absorption saturation in the unpumped section, which describes both the wavelength shift and the threshold current variation. The increase in threshold current that we observe is much smaller than results reported in the literature for GaAs/AlGaAs lasers, where a large exponential dependence was attributed to gain saturation in the pumped section. Because the threshold current does not dramatically vary with unpumped length for our lasers, this is a potentially useful technique for shifting the output wavelength of the laser. Finally, we investigate the wavelength tuning behavior of lasers having two segments pumped with different currents. A wavelength tunability of ~13 nm for the DQW laser was observed.
Long-wavelength ridge-wave-guide lasers with processed facets and integrated back-facet monitors
Authors: Cook J. P. D. , Dzioba S. , Fox K. , Maritan C. , Marks J. , McGarry S. , Shepherd F. R. , Svilans M. , Rousina R.
Published: April 2011

InP–InGaAs cleaved-cavity lasers are routinely used in long-wavelength optical transmission systems, packaged with a discrete pin photodiode back-facet monitor used to provide feedback to control the laser output power. This conventionally requires two separate wafer-fabrication processes, and individual testing, cleaving, and assembly at the chip level. The handling of cleaved bars, facet-coating, testing, and mounting is labour-intensive and expensive. Etching mirror facets during wafer processing makes it possible in a single fabrication process to fabricate lasers with an integrated back facet monitor, and do on-wafer testing without further alignment and assembly. This has now been achieved with the following technologiesf (i) laser epitaxial layers used for light detection as well as emission, (ii) reactive-ion-etched (RIE) (CH4–Ar)-etched mirror facets, and (iii) electrical interconnects by metal airbridges. Integrated laser and (or) monitors with RIE-processed facets have threshold currents as low as 30 mA, efficiencies of 0.14 mW mA−1, and monitor efficiencies of 0.1 mA mW−1. Excellent uniformity was observed across a 2 in (1 in = 2.54 cm) wafer. The lower threshold currents (27 mA) observed for cleaved facet lasers from the same wafer indicate that the processed facet quality can be further improved; the optimum RIE process results in etched facets with a facet angle about 5° off vertical. Packaged devices have been successfully operated at speeds up to 1 Gb s−1 for both laser and monitor. Preliminary reliability studies are described.
Echelle grating – curved wave-guide demultiplexer for photonic integrated circuits
Authors: Fallahi M. , McGreer K. A. , Delage A. , Normandin R. , Templeton I. M. , Barber R. , Chatenoud F. , Champion G.
Published: April 2011

A grating spectrometer integrated with curved output wave guides was designed and fabricated in GaAs–AlGaAs waveguide structure for use in the 1 μm wavelength range. By incorporating curved wave guides, a larger separation between output facets was obtained. This is desirable for future integration. High-quality patterns were fabricated by focused ion beam lithography and reactive ion etching. Eight outputs with a channel spacing of 2 nm were obtained. The potential of the structure for integration with active components is discussed.
A four-channel ridge wave-guide quantum well wavelength division demultiplexing detector and its optimization
Authors: Ye F. , Moss D. , Simmons J. G. , Jessop P. E. , Landheer D. , Champion H. G. , Templeton I. , Chatenoud F.
Published: April 2011

We present a four-channel wavelength division demultiplexing detector using the principle of quantum confined Stark effect. This device is based on a ridge waveguide GaAs–AlGaAs single quantum well graded index separate confinement heterostructure. Four detectors are fabricated sequentially along the wave guide and their band gaps are tuned to progressively smaller values by applying progressively larger reverse bias voltages. Thus each detector responds preferably to one of the four input wavelengths. For transverse electric polarization, better than −10 dB crosstalk was achieved with a 14 nm wavelength separation. When operated as a three-channel device, better than −15 dB crosstalk was achieved with a 18 nm wavelength separation. For transverse magnetic polarization, better than −10 dB crosstalk was achieved with a 16 nm wavelength separation. We also present a theoretical study that leads to the optimization of the device.
A versatile two-dimensional model for InGaAsP quantum-well semiconductor lasers
Authors: Li Z.-M. , Davies M. , Dion M. , McAlister S. P.
Published: April 2011

We develop a two-dimensional semiconductor laser model suitable for the simulation of strained or lattice-matched InGaAsP lasers. An anisotropic effective mass model is introduced to compute the gain and spontaneous emission spectra of the strained layers. We demonstrate that a simplified band structure model can be used to predict such phenomenon as gain switching in materials under tensile strain. Application examples are given for the design of strained and lattice-matched lasers using the InGaAsP material system.
Gallium arsenide electronics in the marketplace
Authors: Jay. Paul R.
Published: April 2011

The last few years have seen a significant emergence of real product applications using gallium arsenide metal semi-conductor field effect transistor technology. These applications range from large volume consumer markets based on small low-cost GaAs integrated circuits to high-end supercomputer products using very large scale integrated GaAs chips containing up to 50 000 logic gates. This situation represents substantial advances in many areas: materials technology, device and integrated circuit process technology, packaging and high speed testing, as well as appropriate system design to obtain maximum benefit from the GaAs technology. This paper reviews some recent commercial successes, and considers commonalities existing between them in the context of recent technological developments.
Effective mobility in p-channel Si–SiGe metal oxide semiconductor field effect transistors (MOSFETs)
Authors: Manku T. , Nathan A.
Published: April 2011

In this paper calculated results of the effective mobility in p-channel Si–SiGe metal oxide semiconductor field effect transistor (MOSFET) like structures are presented. The mobility is described in terms of a weighted average with the corresponding carrier concentrations at the SiO2–Si interface and the Si–SiGe interface. The carrier concentrations at these two interfaces were obtained by a one-dimensional numerical solution to Poisson's equation, under pertinent boundary and interface conditions. The results indicate a significant enhancement in the effective mobility, if there are no misfit dislocations present at the Si–SiGe interface.
Optimal channel grading in p-type Si/SiGe metal oxide semiconductor field effect transistors (MOSFETs)
Authors: Voinigescu S. , Salama C. A. T.
Published: April 2011

Quantum numerical modelling is employed to show that the cutoff frequency of p-channel Si/SiGe metal oxide semiconductor field effect transistors can be optimized by fully grading the Si1−xGe1−x channel from 0% Ge (at the substrate end) to 40% Ge (at the gate side). A comparison is made with previously reported, partially graded channel devices. The valence band potential drop owing to Ge grading is shown to provide sufficient isolation between the free carriers in the channel and the acceptor atoms in the δ-doped layer underneath. A simple formalism is used to calculate saturation region cutoff frequency from one-dimensional simulations and to show how free carrier mobility profiles can be obtained from low-frequency small-signal measurements.
Nonlinear behaviour in the magneto-transport through continuous gate and split gate nanostructures
Authors: Taylor R. P. , Fortin S. , Sachrajda A. S. , Adams J. A. , Coleridge P. T. , Zawadzki P. , Davies M. , Marshall P.
Published: April 2011

Quantum point contacts (QPCs), defined by surface gate technology, are increasingly featuring as basic building blocks of more sophisticated geometries such as coupled dot, single electron, and coherent wave devices. For many of its potential roles the electron density within the QPC needs to be known accurately as a function of the voltage applied to the split gates that define the QPC within the two-dimensional electron gas. A common characterization technique extracts the density from the positions of the conductance plateaus that result from the depopulation of edge states as the gate voltage is swept at high magnetic fields. We study the high current breakdown of these plateaus and investigate the nonlinear current–voltage characteristics for both split gate and continuous gate geometries. We demonstrate that the breakdown is not centred around the plateaus and that, unlike the breakdown of the quantum Hall effect, a forward propagation mechanism needs to be considered and indeed is the dominant process.
Experimental investigation of the influence of the barrier thickness in double-quantum-well resonant interband tunnel diodes
Authors: Yang Rui Q. , Lu Jian , Xu J. M. , Day D. J.
Published: April 2011

The influence of the central barrier thickness to current–voltage characteristics of double-quantum-well (DQW) resonant interband tunnel diodes are experimentally investigated at room temperature. A peak to valley ratio greater than 100:1 at room temperature is obtained in the device with a central barrier thickness of 20 Å and a well width of 40 Å. (1 Å = 10−10 m).
Carrier lifetimes in strained InGaAsP multiple-quantum-well laser structures
Authors: Takasaki B. W. , Preston J. S. , Evans J. D. , Simmons J. G. , Charbonneau S. , Moss D.
Published: April 2011

We have investigated carrier sweepout in a series of strained InGaAsP multiple quantum well laser structures by time-resolved photoconductivity and CW photoluminescence. The electrons and holes exhibit very different escape times: the electrons less than 0.5 ns and the holes greater than 10 ns. With only the built-in field across the wells, the electron escape is thermally activated in both tensile samples, while it is unclear whether tunneling or thermionic emission is the dominant escape mechanism in the unstrained and compressive samples. Application of a 2 V reverse bias is sufficient to produce efficient tunneling escape of electrons in the tensile samples. A simple model of the competition between thermionic emission and radiative recombination in the tensile wells yields values for the barrier height that are in agreement with the calculated values.
Focused-ion-beam implantation in strained InGaAs-GaAs quantum wells
Authors: Allard L. B. , Aers G. C. , Charbonneau S. , Jackman T. E. , Templeton I. M. , Buchanan M.
Published: April 2011

Photoluminescence spectroscopy (PL) is used to monitor the degree of focused ion beam induced interdiffusion in InGaAs–GaAs quantum wells using 100 keV Ga+ and Si+ ions. The observed transition energy shifts are consistent with the effects of channeling of the incident ions near normal incidence. PL decay times obtained from pulsed excitation experiments at higher dose rates indicate incomplete annealing of defects in the quantum wells resulting in an enhanced nonradiative decay rate. If Si+ ions are implanted instead of Ga+ ions we find a red shift of the PL peak positions at very low doses owing to a doping effect in the quantum wells.
Excited quantum states in CdTe–Cd1−x MnxTe multiple quantum wells and superlattices grown by pulsed laser evaporation and epitaxy
Authors: Labrie D. , Wang X. , Dubowski J. J.
Published: April 2011

The photoreflectance and piezoreflectance spectra of CdTe–Cd0.9Mn0.1 Te multiple quantum wells and superlattices grown by pulsed laser evaporation and epitaxy display series of signatures that are attributed to free exciton transitions occurring between the heavy-hole and light-hole bands, and the upper electron subbands. The signature line positions are in excellent agreement with calculated transition energies obtained from a simple Kronig–Penney model that includes strain effects and the nonparabolicity of the conduction band.
Study of thermal desorption of UV/ozone oxide on InP
Authors: Comedi D. , Balcaitis G. , Robinson B.J. , Thompson D. A.
Published: April 2011

Commercially available (001) InP substrates have been treated by exposure to UV/ozone to produce surface oxide layers suitable for thermal desorption prior to epitaxial growth. Thermally induced changes in composition and structure of the oxidized surfaces in vacuum have been studied using Auger electron spectroscopy (AES), reflection high-energy electron diffraction (RHEED), and Rutherford backscattering/channeling (RBSC). It is found that for temperatures above 440–450 °C the oxide becomes unstable. Thermal oxide desorption in vacuum above 460 °C always results in a P-depleted surface. At 460 °C the oxide can be thermally removed without noticeable P loss; however, the time requried for this process is approximately 2 h. Time-dependent AES results for oxide desorbing at a fixed temperature can be described by assuming a thinning process with a constant thinning rate for short annealing times; however, for longer times the desorption rate increases considerably. After complete oxide removal, the resulting clean (001) InP surface shows a 2 × 1 RHEED pattern, while the corresponding measured In surface peak intensity as measured by RBSC is close to that obtained for a clean MBE grown surface. Significant structural deterioration of the surface is detected at high temperatures (≈ 495 °C) by RHEED nad RBSC. The average O/In composition ratio of the oxide layer has been determined by ion scattering methods.
Microwave-assisted high-speed modulation of semiconductor lasers
Authors: Wu Chung Y. , Guo Chang Z. , Xu J. M.
Published: April 2011

The electron temperature in the active layers of a semiconductor laser can be raised higher than that of the lattice by an externally applied microwave field. This results in a reduction in the optical gain and forms the basis of laser modulation by microwave heating. The gain variation under electron gas heating is calculated. A complete small signal analysis of current modulation, electron heating modulation, and combined or microwave-assisted modulation of semiconductor lasers is presented. In addition, the sensitivities of the electron and photon responses among the three modulation schemes are compared. Some large signal simulation results of high-speed digital modulation are also included.
Sidegating in GaAs metal semiconductor field effect transistors (MESFETs): role of stationary Gunn domains
Authors: McKinnon W. R. , McAlister S. P.
Published: April 2011

We study GaAs 0.8 μm MESFETs that show a threshold for sidegating. In these devices, the current from the sidegate saturates near the threshold voltage, supporting the idea that sidegating is produced when a stationary Gunn domain forms under the channel in the semi-insulating substrate. We compare the metal semiconductor field effect transistor to sidegated resistors and show that the same mechanism applies there, but supplemented by another mechanism, probably associated with the surface.
Electrical characterization of rf sputtered TiN thin films on III–V semiconductors
Authors: Pang Zhengda , Boumerzoug Mohamed , Kruzelecky Roman V. , Mascher Peter , Simmons John G. , Thompson David A.
Published: April 2011

TiN thin films were deposited on GaAs and InP by rf reactive sputtering. Samples of TiN/GaAs and TiN/InP then were investigated by a multitude of techniques to evaluate the morphology of as-deposited and post-annealed films and to investigate contact properties such as barrier height, carrier concentration, and ideality factor. Optical emission spectroscopy was used as an in situ process control to optimize certain film properties. The results show that the deposition conditions, such as total pressure, N2/Ar flow ratio, and substrate temperature, have an important effect on the properties of the resulting films. Under optimized conditions, near-stoichiometric TiN films with resistivities as low as 20 μΩ cm were obtained. Rapid thermal annealing (RTA) of TiN/GaAs enhanced the barrier height and improved the ideality factor of these diodes. These systems were stable after RTA at temperatures as high as 800 °C. As-deposited TiN on InP, in contrast, typically exhibits nonrectifying behaviour. The characteristics become more ohmic after RTA at elevated temperatures.
AlGaAs/InGaAs/GaAs optoelectronic structures on (111)B GaAs
Authors: Chatenoud F. , Janz S. , Normandin R. , Dai H. , McCaffrey J. P.
Published: April 2011

Epitaxial growth and the crystal-orientation specific optical properties of InGaAs quantum wells and AlGaAs surface-emitting harmonic generation wave-guides on (111) substrates are discussed. The samples were grown by molecular beam epitaxy on misoriented (111)B GaAs substrates. Low As4 overpressure and a very high substrate temperature lead to excellent surface morphology for both types of structures, making their growth compatible for later monolithic integration. InGaAs quantum wells are shown to be strongly affected by the strained-induced electric field. We observe an important increase, with In content, of the resultant redshift between (111) and (100) layers; a luminescence redshift as large as 55 meV for an 18% In well is measured. We also demonstrate for the first time surface emission harmonic generation from an all-AlGaAs second harmonic generation wave-guide pumped with 1.06 μm transverse electric (TE) polarized light; as predicted theoretically, the emitted light is uniform along the guide, and as intense as on a (100) crystal for TE–TM (transverse magnetic) interaction.
Transient analysis of signal charge transfer in long diffused regions of spectroscopic image sensors
Authors: Dobson David A. B. , Chamberlain Savvas G.
Published: April 2011

This paper presents the results of a study of charge transfer time in long doped semiconductor regions. These regions are used to collect and store charge in high performance image sensors. The effect of dopant concentration on charge transfer time was studied using a novel two-dimensional device simulation tool. It was found that the delay associated with the long storage region only becomes significant for doping concentrations that are not degenerate. The effect of storage diffusion length on charge transfer time was also studied for degenerately doped structures. For these structures, it was found that the delay is much less than the conventional belief that the delay is proportional to the square of the diffusion dimension the electrons traverse. It was also found that the diffusion dimension affects the charge transfer time indirectly through the back biasing of the transfer metal oxide semiconductor field effect transistor (MOSFET). Shorter diffusions initially cause a larger back biasing of the transfer MOSFET, decreasing the maximum current flow through the device. On the experimental side, novel image sensor devices were designed that incorporate some of the results discussed above. Experimental image sensor structures were analyzed to study charge transfer time and relate the results to the computer simulations.
The electronic structure of molecular beam epitaxy grown InAs (110)
Authors: Swanston D. M. , McLean A. B. , McIlroy D. N. , Heskett D. , Ludeke R. , Munekata H. , Prietsch M. , DiNardo N. J.
Published: April 2011

The initial state dispersion of the two-dimensional electronic surface states on the nonpolar InAs(110) surface has been measured using momentum-resolved photoelectron spectroscopy with synchrotron radiation. The InAs(110) surfaces were grown using molecular beam epitaxy on a GaAs(110) substrate. The A5 surface state, which arises from the surface As lone pair, is split off from the bulk bands away from the surface zone centre and is clearly visible in the photoemission spectra at the high symmetry points ([Formula: see text], [Formula: see text] and [Formula: see text]) of the surface reciprocal lattice. Lower lying surface states overlap more strongly with the bulk bands and consequently it is harder to determine their band dispersion. To alleviate this problem we have applied nonlinear line shape analysis techniques to the valence bands. We demonstrate the viability of this approach to extract the binding energy and width of optical transitions.
Optical and electrical properties of electron cyclotron resonance chemical vapour-deposited SiNx:H films
Authors: Boudreau Marcel , Boumerzoug Mohamed , Kruzelecky Roman V. , Mascher Peter , Jessop Paul E. , Thompson David A.
Published: April 2011

Silicon nitride (SiNx:H) films were deposited on both InP and Si substrates at temperatures ranging from room temperature to 400 °C by electron cyclotron resonance (ECR) plasma chemical-vapour deposition. The silicon source used was ditertiary butyl silane (SiH2(C4H9)2) that was activated by ECR plasmas composed of nitrogen alone or in combination with hydrogen or argon. The effects of various deposition parameters on the film properties are reported. The film indices of refraction ranged from 1.85 to 2.0, while the buffered HF etch rates were as low as 6 Å min−1 (1 Å = 10−10 m). Si/N ratios of the films ranged from 0.70 to 2.5, while the total hydrogen content was found to be approximately 20 to 25 at.%. Incorporation of carbon from the organic silicon source was efficiently suppressed (< 1%) by the addition of a small amount of H2 to the ECR plasma gas. To study the electrical properties of the SiNx:H films, metal–insulator–semiconductor structures were fabricated. Film resistivities as high as 2 × 1015 Ω cm and insulator dielectric constants from 4 to 5 were measured.
Rapid thermal annealing of in situ phosphorus-doped polysilicon emitters
Authors: Mackay Gary F. , Manning Brendon M. , Tarr N. Garry
Published: April 2011

Rapid thermal annealing of in situ phosphorus-doped polysilicon emitter transistors in the temperature range 850–1000 °C greatly reduces the emitter resistance RE at the cost of a slight increase in hole back injection, seen as a decrease in emitter Gummel number GE. Annealing at 1000 °C for 5 s gives low emitter resistance (RE ≈ 100 Ω μm2) while maintaining good suppression of back injection (GE ≥ 1014 scm−4). Annealing at temperatures below 1000 °C fails to reduce RE sufficiently for use in high-speed devices.
Low-frequency noise correlations in lateral pnp bipolar transistors
Authors: Nathan A. , Charbon E. , Kung W. , Salim A.
Published: April 2011

Measurement results of low-frequency noise behaviour, and in particular, the noise correlations in lateral pnp bipolar transistors are presented for various bias conditions in both forward active and saturation regimes. The correlation in output collector noise is very high with a value close to unity only when the device is in medium injection. At extremely high injection, the degree of coherence degrades, depicting a behaviour similar to the forward current gain of the device. This degradation can be attributed to emitter-crowding effects. The correlation in output noise can be exploited to drastically suppress the intrinsic noise, particularly at low frequencies, making such devices useful for the input stage of amplifiers; the first step towards realisation of ultra low-noise amplifiers in standard integrated circuit technology.
Growth of thin CeO2–YBa2Cu3O7 superlattices
Authors: Denhoff M. W. , Grant P. D. , McCaffrey J. P.
Published: April 2011

We have grown a series of CeO2–YBa2Cu3O7 superlattices by pulsed laser deposition. The purpose was to study the growth of an insulator – high temperature superconductor system on a subnanometre scale. This is important for superconducting devices, since the superconducting coherence length is of the order of one to a few nanometres. The scale of the superlattices ranges from a period of about 10 nm down to about 3 nm. The structure of the layers was studied using X-ray diffraction and transmission electron microscopy. We found that superlattices have a coherent, epitaxial structure. The CeO2 follows the Frank – van Merwe growth mode, where the growth proceeds by growing islands about 2 nm thick that coalesce to form a continuous CeO2 layer at an average thickness of 2 nm. We see no evidence of chemical mixing between the YBa2Cu3O7 and CeO2, which implies that they are mutually insoluble at the growth temperature. We have characterized the superconducting properties of the layers using a microwave cavity method at 30 GHz. If the CeO2 layers are thin enough, the superlattices have similar surface resistance and critical temperature as pure YBa2Cu3O7 films.
Optical bistability in the GaAs/AlGaAs bistable field effect transistor
Authors: Ojha Jugnu J. , Vetter Anthony S. , Simmons John G. , Jessop Paul E. , Mand Ranjit S. , SpringThorpe Anthony J.
Published: April 2011

Optical emission is reported from an n-channel GaAs/AlGaAs bistable field effect transistor (BISFET). This emission is found to be strongly correlated with the gate current flowing in the device. Abrupt transitions, referred to as optical switchup and switchdown, are observed in the optical output characteristics as the drain bias is varied, with a switching ratio in excess of 20 dB. These transitions correspond with those seen in the drain and gate currents as the feedback loop from gate to source switches on and off. The transitions exhibit large hysteresis, corresponding to that seen in both the drain and complementary transfer characteristics of the device. The drain voltage at which the optical transitions are observed, and the associated hysteresis, are found to be very sensitive to gate bias, particularly in the saturation region of operation. Implications of the optical characteristics for the carrier flow mechanisms within the BISFET are discussed. Methods of increasing the optical output efficiency of the device are described.
Uniphase operation of a GaAs resistive gate charge-coupled device
Authors: LeNoble Maurice , Cresswell John V.
Published: April 2011

The operation of a GaAs charge-coupled device (CCD) within the UHF band is a technically challenging problem. The GaAs CCDs that were reported previously in the literature were typically operated with multiphase clocks, with the majority operated using clocks in phase quadrature. To provide the multiple UHF clock wave forms with phase correlation to a GaAs CCD demands very stable picosecond timing accuracy between the adjacent clock phases, otherwise unpredictable variations will occur in the device performance. This requirement is difficult to achieve when attempting to incorporate a GaAs CCD in a high-speed analog application, such as the 500 MHz multichannel transient digitizer application being developed at TRIUMF, because of the nonlinear behaviour of the device as a load impedance. In addition to the difficult timing requirement, there are also the electronic circuit disadvantages associated with providing a multiphase clock to a GaAs CCD. The general circuit approach used to provide a multiphase UHF clock consists of splitting or dividing a master clock signal into a set of clock signals with the desired phase properties. The disadvantages of this approach are (i) the circuits are generally narrowband, restricting the range of clock frequencies that can be used; (ii) the circuits usually consume considerable power, producing substantial heat; and (iii) the circuits are typically complex, making them costly and difficult to incorporate with a GaAs CCD. A novel uniphase clock scheme was recently developed at TRIUMF that overcomes the above technical limitations for the UHF operation of a GaAs resistive gate CCD (RGCCD). The method is unique because the static transverse electric field within the GaAs RGCCD channel required to direct the motion of charge is established using the surface potential control offered by the resistive gates, under dc-biassed conditions. This permits a simple planar device comprising four electrodes per pixel to be used instead of a more elaborate castellated or ion-implanted device. Application of a single clock signal to the GaAs RGCCD provides the required temporal transverse electric field variation to cause charge motion to occur. Charge transfer efficiencies exceeding 0.999 have been achieved with a 128 pixel GaAs resistive gate CCD using (1) a fixed frequency uniphase clock operating below 100 MHz and (2) using a triggered dual frequency uniphase clock operating at 500 MHz during the signal acquisition period and at 15.6 MHz during the signal expenditure period.