bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Heteroepitaxy and Characterization of Inp and GaInP on Silicon for Solar Cell Applications
Authors: Al-Jassim M.M. , Ahrenkiel R.K. , Wanlass M.W. , Olson J.M. , Vernon S.M. 
Published: March 2011

ABSTRACTInP and GaInP layers were heteroepitaxially grown on (100) Si substrates by atmospheric pressure MOCVD. TEM and photoluminescence (PL) were used to measure the defect density and the minority carrier lifetime in these structures. The direct growth of InP on Si resulted in either polycrystalline or heavily faulted single-crystal layers. The use of GaAs buffer layers in InP/Si structures gave rise to significantly improved morphology and reduced the threading dislocation density. The best InP/Si layers in this study were obtained by using GaAs-GaInAs graded buffers. Additionally, the growth of high quality GaInP on Si was demonstrated. The minority carrier lifetime of 7 ns in these layers is the highest of any III-V/Si semiconductor measured in our laboratory.
Optimisation Of The Heteroepitaxy Of Ge On GaAs For Minority-Carrier Lifetime
Authors: Venkatasubramanian R. , Timmons M.L. , Bothra S. , Borrego J.M. 
Published: March 2011

ABSTRACTGrowth of Ge on GaAs at reasonably high temperatures, which produce better crystallinity in the Ge, presents serious difficulties due to the dissociation of the GaAs substrate. In this paper, we describe the growth of a lowtemperature buffer layer of Ge on GaAs that prevents decomposition of the GaAs during high-temperature growth of Ge. Using this approach, we present the first report of highly specular, mass-transport-limited high-temperature growth of Ge on GaAs that is comparable to the homoepitaxy of Ge. The factors affecting the minority-carrier lifetime of Ge on GaAs, using such an epitaxial growth technique, were studied with a non-invasive microwave technique. Lifetime variations, from very low values to about 0.45 μsec, were obtained as a function of the growth conditions. Significantly, the removal of the surface oxide on the GaAs substrate prior to low-temperature buffer-layer growth, terminating the flow of germane(GeH4) during the ramp to high growth temperatures, thinner buffer layers, and high-temperature growth of Ge were found to be important for obtaining long lifetimes.
Alternative Chemistries for Mocvd Growth of III/V Materials
Authors: Lum R.M. , Klingert J.K. 
Published: March 2011

ABSTRACTAlkyl substituted arsine compounds, RnAsH3–α are attractive alternatives to arsine, AsH3. for metalorganic chemical vapor deposition (MOCVD) of GaAs-based compounds because they are typically low vapor pressure liquids which can be stored and handled more safely than the high-pressure gas cylinders used for AsH3. Despite their increased safety, the alkylarsines have not been widely used due to carbon incorporation problems and high background doping levels in the deposited films. To determine the impact of alternative growth chemistries on MOCVD processes we have investigated the thermochemistry controlling the decomposition of AsH3 and its alkyl substitutes. Data are presented on the thermal stability of the Ascompounds, their resulting growth properties, and the composition and formation kinetics of the volatile products formed during thermal decomposition in an H2 ambient. The gas phase reactions controlling decomposition are identified. The implications of our results for CVD growth models and the potential of alkylarsine compounds for different CVD processes are discussed.
Mbe Growth of Strained-Layer InSb/InAlSb Structures
Authors: Whitehouse C.R. , Mcconville C.F. , Williams G.M. , Cullis A.G. , Barnett S.J. , Saker M.K. , Skolnick M.S. , Pitt A.D. 
Published: March 2011

ABSTRACTThe MBE growth and related materials characterisation of InSb/InAlSb strained-layer structures is described. Band-gap considerations and critical thickness calculations are presented and indicate that this material system should offer considerable device potential. Detailed structural studies, performed using both transmission electron microscopy and X-ray diffraction, confirm the growth of high quality multiple quantum-wells, and 2K photoluminescence has shown corresponding energy upshifted transitions.
Einstein Rzlation in Quantum Wires of Tetragonal Sediconduc Tors
Authors: Ghatak Kamakhya P. , De B. , Mondal M. , Biswas S. N. 
Published: March 2011

ABSTRACTWe have studied the Einstein relation for the diffusivity. mobility ratio (7PT) on the basis of a newly derived electron energy spectrum in QW f tetragonal semiconductors, within the framework of K. P method by considering all types of anisotropies of the energy band parameters. It is found, taking n-Cd3 As2 as an example that the DUTZ increases with electron concentration and decreases with film thickness in an oscillatory manner respectively. The theoretical results are in good aoreement with the suggested experimental method of determining the DMR in degenerate semiconductors having arbitrary dispersion law.
Characterization of Mbe GaAs Layers Grown at 200°C–300°C
Authors: Wie C.R. , Xie K. , Bardin T.T. , Pronko J.G. , Look D.C. , Evans K.R. , Stutz C.E. 
Published: March 2011

ABSTRACTLattice parameter, RBS channeling, and T-dependent Hall effect and resistivity are measured in 5 μm GaAs layers MBE-grown at 200°C, 250°C and 305°C, and subsequently annealed. Perpendicular lattice parameter was increased by 0.15% for 200 °C, 0.10% for 250°C, and 0.05% for 305°C sample. No parallel mismatch was observed. In annealing up to 800°C, most recovery of lattice parameter occured at 350°C-450°C. For samples annealed at 500° C − 600°C, the conductivity activation energy was higher in the furnace annealed sample than in the RTA-annealed sample, indicating possible depth nonuniformity in furnace annealed sample. The 600°C RTA annealed sample indicated a donor activation energy of 0.61 eV. A 600°C furnace annealed sample indicated the deep donor concentration of 1.5×1018 cm−3. Maximum mobility in the 500–600°C annealed sample was 3000–3500 cm2/Vs, limited by the neutral impurity scattering and polar optical phonon scattering.
A Novel Approach to the Assessment of Semiconductor Hetero-Interfaces in Multilayer Structures
Authors: Rimmer J.S. , Missous M , Peaker A.R. , Hamilton B. 
Published: March 2011

ABSTRACTWe demonstrate the novel use of CV simulation to determine the level of charge at each interface in multilayer GaAs/AlGaAs heterostructures. The gettering of charged centres at the earliest grown interfaces is quantitatively appraised and the parallel application of PL decay lifetime measurements determines their effectiveness as recombination centres. A direct relationship is found between the magnitude of the charged states and the recombination velocity. Estimates of a 1eV activation energy and a hole capture cross section of 10−15 cm2 were also obtained. This suggests that the dominant recombination centre could be observed as a hole trap.
The Influence of Substrate Patterning on Threading Dislocation Density and Residual Stress in GaAs/Si Heteroepitaxial Layers.
Authors: Sohn Hyunchul , Weber Eicke R. , Tu Jay , Lee Henry P. , Wang Shy 
Published: March 2011

ABSTRACTThe growth of GaAs films by MBE on mesa-type patterned Si substrates has been investigated. Mesa widths were varied from 10 µm to 200 µm and were prepared using chemical etching with Si3N4 masks and reactive ion etching. The residual stress in the epitaxial layer was estimated using low temperature (7K) photoluminescence and the defect distribution was studied by cross sectional TEM, dislocation densities were in addition determined by etch pits. The residual stress and the dislocation density decreased monotonically with the reduction of growth area. By the incorporation of strained layers with the reduction of growth area, the etch pit density in GaAs layers on mesas was reduced further.
Luminescence of Mbe SimGen Strained Monolayer Superlattices
Authors: Kallel M. A. , Arbet-Engels V. , Karunasiri R. P. G. , Wang K. L. 
Published: March 2011

ABSTRACTSimGen strained monolayer superlattices (SMS) have been fabricated by molecular beam epitaxy (MBE) and characterized using photoluminescence (PL). Symmetrically strained structures with different periodicities have been grown on top of a Si1−xGex alloy buffer layer. Luminescence features below (above) the Si (Ge) energy bandgap have been observed and attributed to either dislocations in the buffer layer or to energy band transitions in the SMS.
Confinement of Threading Dislocations in Simox with a GeSi Strained Layer
Authors: Namavar F. , Cortesi E. , Perry D.L. , Johnson E.A. , Kalkhoran N.M. , Manke J.M. , Karam N.H. , Pinizzotto R.F. , Yang H. 
Published: March 2011

ABSTRACTWe have investigated improving the crystalline quality of epitaxial silicon grown on SIMOX by confining threading dislocations in the original Si top layer using a GeSi strained layer. Epitaxial Si/GeSi/Si structures were grown by CVD on SIMOX and Si substrates with a GeSi alloy layer about 1000 − 1500 angstroms thick with Ge concentrations of about 0−20%. A Ge concentration in the alloy layer of about 5.5% or higher appears to be necessary in order to bend any of the threading dislocations from the original SIMOX top layer. For a higher Ge concentration of about 16%, most of the threading dislocations appear to be bent and confined by the GeSi layer. In addition, the GeSi strained layers grown by CVD (at about 1000°C) appear to be high quality and no misfit dislocations were observed in the regions studied by XTEM and plane view TEM.
Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.
Authors: Houghton D.C. , Rowell N.L. 
Published: March 2011

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.
Island Formation in Ge on Si Heteroepitaxy
Authors: Eaglesham D.J. , Gossmann H.-J. , Cerullo M. 
Published: March 2011

ABSTRACTWe present a study of island formation (the transition from 2D to 3D growth) during the Stranski-Krastanow (S-K) growth of Ge on Si. The energetic driving force for S-K island formation should be the ability to relax the islands by dislocation introduction. Here, we show that Ge islands formed on Si (100) are initiallydislocation-free, in the presence of a 2D “sea” that is far in excess of the equilibrium 3 monolayers (ML). We call this phase of growth “dislocation-free S-K”. The 2-D sea does not collapse until dislocated islands are produced at an average coverage of = 7 ML. We call the dislocation-free island phase “coherent S-K” growth. The corresponding 2D-3D transition on Si (111) appears to reach equilibrium far faster, and we have not observed dislocation-free island formation: dislocated islands are seen at = 5 ML. As expected, the kinetics allow us to suppress island formation on (100) by reducing the growth temperature. These thick 2D films are analogous to those grown on As-covered surfaces, but have a microstructure dominated by edge dislocations.
Photoluminescence from Coherently Strained Si1−xGex Alloys
Authors: Rowell N.L. , Noël J.-P. , Houghton D.C. , Perovic D.D. 
Published: March 2011

ABSTRACTAn intense, broad photoluminescence PL peak, with an internal quantum efficiency as high as 31%, has been observed from a variety of structures containing Si1−xGex strained layers on Si(100) substrates; i.e. Si1−xGex thick random alloy layers, single quantum wells (SQW) and multiple quantum wells (MQW) with layers thick enough so that zone folding effects were not relevant. This peak, which shifted consistently and predictably with Ge concentration( 0.06 < × < 0.53), had its high energy edge near the established band gap for strained SiGe. PL excitation spectroscopy indicated that no phonons were involved in the process causing the SiGe PL peak. Samples deposited at ~ 400 °C exhibited low PL intensity, whereas annealing at ~ 600 °C enhanced the intensity by as much as two orders of magnitude. This anneal treatment was found to remove grown-in defect complexes without creating a significant density of misfit dislocations. The PL peak energy at 4.2 K varied from 620 to 990 meV for Ge fractions x from 0.53 to 0.06. When the samples were forced to relax, e.g. by higher temperature annealing, the luminescence of this peak either shifted to near the relaxed bandgap or was quenched by deep, dislocation related states. Prior to such relaxation, the efficient PL was due to exciton accumulation in the strained Si1−xGex layers of single and multiple quantum wells, where the bandgap was locally reduced. It is suggested that the recombination of electrons and holes occuring within a high-density electron hole condensate (EHC) can cause the observed spectrum.
Gas Source Si-Mbe
Authors: Hirayama Hiroyuki , Hiroi Masayuki , Koyama Kazuhisa , Tatsumi Toru 
Published: March 2011

ABSTRACTGas source Si molecular beam epitaxy (Si-MBE) apparatus has been devised. The growth mechanism was studied using reflection high energy electron diffraction (RHEED) intensity oscillation. Si epitaxial layers grew through a dissociative adsorption of Si2H6 molecules on Si surfaces. This dissociative adsorption enables a selective epitaxial growth on SiO2 patterned Si wafers. At low temperatures, the growth rate was limited by a desorption of hydrogen which terminates surface dangling bonds. Doping with B, Sb and P were also studied. B doping was achieved using HBO2 Knudsen cell or B2H6 gas dopant. Sb doping used an ionized doping cell. P doping was achieved using PH3 gas dopant. The effect of B doping on the growth was studied using RHEED oscillation. A doped layer's selective epiataxial growth was possible by selective epitaxial growth under doping. This technique was applied to bipolar transistor fabrication. Moreover, using GeH4, Si1−xGex compound growth and its selective epitaxial growth was achieved. Using this Si1−xGex selectively grown layer, a Si1−xGex base heterobipolar transistor (HBT) was also fabricated. An electron cyclotron resonance (ECR) gas source Si-MBE cell was used for a low temperature surface cleaning and a surface termination by atomic hydrogen.
Carbon Doped Silicon Emitters Fabricated Using Limited Reaction Processing
Authors: Ruddell F.H. , Armstrong B.M. , Gamble H.S. , Affolter K.B. , Moynagh P.B. , Rosser P.J. 
Published: March 2011

ABSTRACTThis paper describes the deposition of in-situ doped N-type silicon carbide layers in a Limited Reaction Processing (LRP) reactor. Silane/propane/ phosphine gas chemistry was used at temperatures less than 1000°C and SIMS, XPS and TEM analysis techniques aided layer characterisation. A low thermal budget deposition process (1 min at 970°C) was employed to form the emitters of Sic/Si heterojunction NPN bipolar transistors. These devices yielded a factor of two increase in emitter Gummel number compared to diffused emitters.
Characterization and Griwth of Oicanic Multiple Qanm Well Structures
Authors: So F.F. , Forrest S.R. , Shi Y.Q. , Steier W.H. 
Published: March 2011

ABSTRACTMultiple quantum well structures consisting of alternating layers of two crystalline organic semiconductors, namely, 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) and 3,4,7,8 naphthalenetetracarboxylic dianhydride (NTCDA), have been grown by organic molecular beam deposition. The layer thickness was varied from 10 to 200 Å. Birefringence measurements indicate that there is a strong structural ordering in all PrCDA layers, although the PrCDA and NTCDA crystal structures are incommensurate. From optical absorption measurements, it is found there is a blue shift in the lowest energy PICDA singlet exciton line with decreasing layer thickness. A model based on exciton quantum confinement is proposed to explain the energy shift. We have measured the low temperature photoluminescence spectra of organic quantum well structures, and found a slight red shift in the spectra with decreasing well width. These results are also discussed.
Nucleation and Growth Mechanisms in Hetero-Epitaxial Films
Authors: Venables J.A. , Drucker J.S. , Krishnamurthy M. , Raynerd G. , Doust T. 
Published: March 2011

ABSTRACTNucleation and growth mechanisms in the formation of heteroepitaxial films are reviewed. The various processes can be incorporated into rate equations to model the number density and size distribution of clusters.Recent work on extensions of this approach to include the effect of surface steps and other surface imperfections is highlighted.The most important processes are being studied experimentally using a combination of surface-analytic and -microscopic techniques, based on SEM and STEM instrumentation. Recent examples are given in which nucleation densities, surface diffusion lengths and the effects of steps have been studied in the systems Ag/Si(lll) and Ge/Si(100).
Preparation of Cross-Sectional TEM Samples of PbTe and CdxPb1−x Te on BaF2
Authors: McCaffrey John P. , Das Suhit R. , Cook John G. 
Published: March 2011

ABSTRACTEpitaxial PbTe and CdxPb1−xTe films have been grown on single crystal (111) BaF2 by low energy bias sputtering, and have been analyzed by transmission electron microscopy (TEM) and transmission electron diffraction (TED). Preparation of suitable cross-sectional TEM samples was made difficult by the tendency of the substrate to cleave apart during dimpling, and by the epoxy forming bridges across the sample during atom milling. Suitable preparation techniques were developed employing back-polishing the BaF2 substrates to <0.2 mm thickness, using a suitable epoxy, and shielding the argon atom beam during milling to prevent milling parallel to the surface. In cases where an epoxy bridge did form across the sample, the bridge was broken manually or by atom milling, depending upon the area of sample which was being investigated. These techniques are applicable to other materials which produce similar problems during TEM sample preparation.
The Role of Ultramicrotomy in the Microstructural Studies of Rapidly Solidified Aluminium Alloy Powders
Authors: Chowdhury A. J. S. , Freundlich A. , Sheppard T. 
Published: March 2011

ABSTRACTThe as-produced high hardness of rapidly solidified aluminium powder alloys make TEM specimen preparation difficult. Conventional methods, i.e. electrothinning or ion-beam thinning of electroplated foils or compacts, although adequate for some powders, are not suitable for many other new and novel alloy powders. In this paper we discuss ultramicrotomy of such powders and the prospects and limitations of the method.
Fabrication of Planar and Cross-Sectional TEM Specimens Using a Focused Ion Beam
Authors: Young R. J. , Kirk E. C. G. , Williams D. A. , Ahmed H. 
Published: March 2011

ABSTRACTA new technique using a focused ion beam has been developed for the fabrication of transmission electron microscopy specimens in pre-selected regions. The method has been proven in the fabrication of both cross-sectional and planar specimens, with no induced artefacts. The lateral accuracy achievable in the selection of an area for cross-sectional analysis is better than one micrometre. The technique has been applied to a number of silicon and III-V based integrated circuits, and is expected to be suitable for many other materials and structures.
A Technique for Preparing “Two in One” Cross-Sectional TEM Specimens
Authors: Ma Guang-Hwa M. , Chevacharoenkul Sopa 
Published: March 2011

ABSTRACTA modified “two-in-one” cross-sectional TEM sample preparation technique is described. By coating a thin layer of “marker” to distinguish one sample from the other, two samples could be simultaneously prepared in one TEM cross-sectional specimen. Therefore, the specimen preparation time is reduced by nearly one half. The coating can be done in an existing ion-mill. Criteria for choosing a suitable marker as well as tips on getting good quality specimens are described. An example of applying this technique to a processing-microstructure study of an ultra-shallow junction formation in silicon is demonstrated.
Experimental Measurement of Transmission Electron Microscope Specimen Temperature during Ion Milling
Authors: Bahnck D. , Hull R. 
Published: March 2011

ABSTRACTSemiconductor materials and devices are commonly investigated by transmission electron microscopy to obtain microstructural information. The results are useful only when a thinned sample is representative of the parent material. The technique of ion milling can introduce artifacts arising from beam heating during specimen preparation. A survey of specimen temperatures during argon and iodine ion milling of silicon, indium phosphide and gallium arsenide was made by encasing a thermocouple in a specimen and varying ion beam energy and beam angle of incidence. The results indicate, for example, that the typical temperature of silicon specimen preparation is less than 140°C. By decreasing the beam energy and incident angle, the milling temperature can be reduced. Design improvements on the ion mill can also sink heat away from the specimen.
Wedge Cleaving and Ultramicrotomy as Alternative TEM Sample Preparation Methods in Materials Science
Authors: Ruterana P. , Laub D. , Buffat P-A. 
Published: March 2011

ABSTRACTThe use of two methods for preparation of TEM samples has been investigated. It has been possible to show the practical details of the wedge cleaving method and illustrate it with original results on III-V semiconductors and on metallic thin layers on Silicon. Chemical etching of AlGaAs in heterostructures was clearly observed and can further be quantified. Preferred oxidation of AlAs was shown to be important this can be a problem to a faithful interpretation of images from cross section samples prepared in more conventional ways. Efficient microtomy for use in materials science is still in the development stage, however we think to have found the best conditions for sectioning very soft metals like copper. We hope to decrease the compression in these materials by using lower angle diamond knives
Rapid Preparation of Cross-Sectional TEM Samples from Electroplated Copper
Authors: Dinan T. E. , Landolt D. , Ruterana P , Buffat P.-A. 
Published: March 2011

ABSTRACTMethods were investigated for the rapid preparation of cross-sectional TEM samples from electroplated copper. Electropolishing and ultramicrotomy were used. The electropolished samples were sandwiched in a copper/nickel alloy and electropolished using a nitric acid/methanol mixture. Large transparent areas were obtained and it was possible to position the area of interest at the point where the hole would appear. Ultramicrotomed samples cut with 45° diamond knives were electron transparent but the crystalline structure of the sample was severely damaged. However, it was possible to identify the conditions by which good ultramicrotomed samples might be produced in the future.