bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct In-Situ Observation of Charge Carrier Separation During Formation of an Amorphous Silicon / Crystalline Silicon Heterojunction
Authors: Neitzert H. C. , Hirsch W. , Kunst M. 
Published: March 2011

ABSTRACTThe signal of the Transient Microwave Detected Photoconductivity after laser pulse illumination is followed during the PECVD growth of intrinsic amorphous silicon on top of crystalline silicon (c-Si) substrates. Depending on the thickness of the amorphous layer the observed phototransients can be assigned to the excess charge carriers in different regions of the so grown heterojunction. For thin a-Si:H layers the signal amplitude decreases exponentially with deposition time. In the case of thick amorphous silicon the signal reflects only the properties of the amorphous silicon and the signal amplitude is constant. In an intermediate range a large contribution of charge carriers absorbed in the a-Si:H and subsequently transported to the crystalline part of the heterostructure to the measured signal can be observed. Due to their much higher mobility in the crystalline layer these excess charge carriers become visible only after reaching the crystalline silicon. This leads to the observed delay of the TRMC signal amplitude relative to the exciting laser pulse. The experiments show, however, that this charge carrier transfer takes place only in the case of a low defect a-Si:H layer to a measurable extent and is suppressed by the low carrier mobility in highly defective a-Si:H deposited at lower substrate temperatures.
Photoinduced Space-Charge Gratings in Semi-Insulating Multiple Quantum Wells
Authors: Wang Q. , Brubaker R. M. , Nolte D. D. , Melloch M. R. 
Published: March 2011

ABSTRACTHigh-order spatial harmonics of photo-induced space-charge gratings are observed in semi-insulating photorefractive quantum wells. Two-wave mixing combined with four-wave mixing in holographic thin films can provide a versatile probe of absorption and photorefractive gratings.
New Concept of Multilayer Photorefractive Device
Authors: Viallet Jean Emmanuel , Picoli Gilbert , Gravey Philippe 
Published: March 2011

ABSTRACTWe propose a multilayer photorefractive device based on the association of two classes of materials respectively designed for transport and electro-optic properties. This device consists in repeated elementary cells, each of them made with an electro-optic material layer embedded between two different photoconductive layers. In these layers (respectively hole and electron dominated) deep levels allow to build-in a space charge field distribution under periodic illumination, giving rise in the electro-optic layer to a perpendicular electric field component, yielding to a diffraction grating. Its efficiency can be increased by the repetition of these cells. InGaAsP/InP MQW can be used as electro-optic material and semi-insulating InP:Ti and InP:Fe as respectively electrons and holes dominated photoconductors. We present simulation results of the behaviour of this device under electric bias and of the coupling effects between adjacent layers which yield space charge field modulation well over the usual diffusion limit.
Surface Charge Imaging in Semiconductor Wafers by Surface Photovoltage (SPV)
Authors: Edelman Piotr , Lagowski Jacek , Jastrzebski Lubek 
Published: March 2011

ABSTRACTWe present fast, wafer-scale imaging of the surface charge achieved via non-contact measurement of the surface potential barrier by surface photovoltage (SPV) under high excitation levels. The approach is capable of resolving surface charge differences as small as 108 q/cm2. Fundamentals of surface charge imaging are discussed, and the method is compared with standard SPV contamination mapping. Examples include problems relevant to silicon IC fabrication and surface charge maps of GaAs and InP.
Electro-Optical Studies of Vanadium in GaP by Space Charge Spectroscopies
Authors: Bremond Georges , Guillot G. , Roura P. , Ulrici W. 
Published: March 2011

ABSTRACTA complete understanding of the electrical and optical properties of the Vanadium related donor level (VGa3+/VGa4+) in GaP is deduced from a number of different characterization techniques (deep level transient and deep level optical spectroscopies, optical absorption) performed on p-type V doped GaP. The VGa3+/VGa4+ donor level is located at Ev+0.25eV. This assignment is based on the correlation of optical absorption spectra and the photoneutralization cross-section σp°(hv) curve obtained by deep level optical spectroscopy confirming that this technique is very unique for deep level identification in semiconductor materials.
Deep Level Energy Analysis of Surface and Bulk Defects Using a Noncontact Laser/Microwave Photoconductance Technique
Authors: Buczkowski A. , Rozgonyi G. A. , Shimura F. 
Published: March 2011

ABSTRACTA noncontact technique for deep level energy analysis has been discussed based on a laser excitation/microwave reflection transient photoconductance procedure. An algorithm for separation of surface and bulk recombination effects was developed to independently determinesurface and bulk energy states. Deep energy levels associated with trapping and recombination processes have been calculated from the temperature dependence of surface recombination velocity and bulk recombination lifetime, based on state occupation statistics. Results have been compared with conventional DLTS data for silicon samples intentionally doped with metals during crystal growth.
Dynamic Operation of Quantum Well Seed's (Invited)
Authors: Chirovsky Leo M. F. 
Published: March 2011

ABSTRACTThis paper describes methods of operating Quantum Well SEED's, which utilize the dynamic properties of the devices and thereby forego the need for optical bistability. The major advantages of dynamic operation versus the conventional modes utilizing optical bistability are that much less total optical energy is needed per cycle and/or much faster operation is possible due to much shorter switching times. Such dynamic modes of operation do require a more careful rationing of optical energy from external laser sources and require that the devices have much higher output contrast ratios.
Nondestructive Characterization of ZnSe/GaAs Heterostructure Using Transverse Acoustoelectric Voltage Spectroscopy
Authors: Han K. J. , Abbate A. , Bhat I. B. , Akram S. , Das P. 
Published: March 2011

ABSTRACTThe electrical and optical properties of the heterostructure interface between high resistivity ZnSe and the semi-insulating GaAs substrate have been investigated using Transverse Acoustoelectric Voltage (TAV) spectroscopy. From the TAV spectra and the relative change of the TAV amplitude (ΔTAV/TAV), we have found the carrier type and concentration of ZnSe as well as the energy levels of various trap states at the heterostructure interface. The spectral behavior of the ΔTAV/TAV curves varied for samples of different ZnSe epilayer thickness. From the measurements, the surface recombination velocities (SRV's) were calculated. For the pseudomorphic ZnSe films on GaAs, a reduction in the SRV's was measured. As the thickness of the ZnSe film was increased, the various ΔTAV/TAV indicated presence of a large number of interface states due to the introduction of misfit dislocations.
Laser-Assisted Growth of ZnSe by Metalorganic Molecular Beam Epitaxy
Authors: Coronado C. A. , Ho E. , Kolodziejski L. A. , Huber C. A. 
Published: March 2011

ABSTRACTBy employing metalorganic molecular beam epitaxy (MOMBE), the heteroepitaxy of ZnSe on GaAs has been achieved using diethylselenium and diethylzinc. Significant (10x ∼ 15x) growth rate enhancement has been observed when radiation from an argon ion laser is incident to the surface; photons with energies greater than the bandgap at the growth temperature contribute to the enhancement. Photo-thermal effects are ruled out due to the low power densities used (∼200 mW/cm2). Growth rate enhancementis found to be a function of substrate temperature, VI/II gas flow ratio, laser wavelength and intensity. To further understand the effect of the laser on ZnSe growth, solid sources of Zn and Se are used in conjunction with metalorganic gas sources. The effect of laser illumination is found to depend on the combination of precursors employed: both growth rate enhancement and growth rate suppression are observed. Laser-assisted growth has application for achieving. selective area epitaxy and for tuning the surface stoichiometry.
Relationship between Self-Texture and Interfacial Restriction on the Epitaxy of ZNO Thinfilms I
Authors: Fujimira Norifumi , Goto Seiki , Ito Taichiro 
Published: March 2011

ABSTRACTWe investigated relationships between self-texture and interfacial restriction on the epitaxy of directed, bonded, thin films. Defect structures in ZnO films grown epitaxially on (0001)sapphire mere evaluated by 3—dimensional maping of k—spacing using an X—ray double crystal spectrometer. The orientation distribution and variation in lattice spacing of the films wre individually measured to elucidate the mechanism of growth. The growth mode was found to change at a film thickness of approximately 100 Å. The layer within 100Å of the interface had a small orientation distribution (1.8'), a large lattice spacing distribution, and a large cumpressive stress.The layer that was more than 100Å from the interface had a larger orientation distribution, a smaller lattice spacing distribution, and a smaller compressive stress.
In-Situ Characterization of AlGaAs Layers Grown by Chemical Beam Epitaxy Using Dynamic Optical Reflectivity
Authors: Armstrong John V. , Farrell Trevor 
Published: March 2011

ABSTRACTCharacterization of A1GaAs layers grown in a VG-V80H chemical beam epitaxy chamber was achieved using dynamic optical reflectivity (DOR). The reflectivity for both stationary and rotating substrates was measured using a normal incidence visible laser. The DOR technique was used to measure the complex refractive index and the growth rate of the layer.The composition of the AlGaAs layer was then obtained from the published variation of refractive index with aluminum fraction. Using the refractive indices determined by DOR, good agreement with theory was achieved for the reflectivity trace from a AlGaAss/GaAs superlattice structure.
Epitaxial YSi2−x and ErSi2−x Thin Films on (111) Silicon
Authors: Lee T.L. , Su W.D. , Chen L.J. 
Published: March 2011

ABSTRACTEpitaxial RSi2−x (R = Y and Er) has been grown on (111)Si by solid phase epitaxy in ultrahigh vacuum deposited metal thin films on silicon. The evolution of vacancy ordering and defect structure in epitaxial YSi2−x. and ErS2−x thin films on (111)Si have been studied by both conventional and high resolution transmission electron microscopy.Superlattice spots located at ⅓{2110} in [0001]RS2−x, diffraction patterns are attributed to the formation of ordered vacancy structure in the Si sublattice planes. The splitting of extra diffraction spots is correlated to the formation of an out-of-step structure. Streaking of the split diffraction spots in the diffraction pattern is attributed to the presence of an out-of-step structure with a range of M values. The M was found to settle down to a fixed value after high temperature and/or long time annealing.Planar defects in RSi2™x films were analyzed to be stacking faults on {1010} planes with ⅙<1213> displacement vectors. Computer simulation was carried out to model the atomic structure of stacking fault in YS2−x-. thin films. The simulated images are seen to match rather well with experimental images taken under two different values of defocus.
Formation of The Interface between InP and Arsenic Based Alloys by Chemical Beam Epitaxy
Authors: Tamargo M. C. , Brasil M.J.S.P. , Nahory R. E. , Aspnes D. E. , Philips B. , Hwang D. M. , Schwarz S. A. , Quinn W. E. 
Published: March 2011

ABSTRACTWe investigate the formation of inAs-rich layers at the interface between InP and arsenicbased Ill-V alloys grown by chemical beam epitaxy (CBE). In-situ spectroscopic ellipsometry, low temperature photoluminescence, secondary ion mass spectrometry and transmission electron microscopy were used to characterize the formation of these layers. We present evidence for interfacial layer roughness that depends strongly on growth temperature and on the presence of surface steps, and show that modifications of the interface chemistry and of the gas-switching sequence can reduce interfacial layer thicknesses.
Van Der Waals Epitaxy of GaSe on WSe2
Authors: Lang O. , Schlaf R. , Tomm Y. , Pettenkofer C. , Jaegermann W. 
Published: March 2011

ABSTRACTGaSe layers were grown on the van der Waals (0001) planes of WSe2 (van der Waals epitaxy). The substrate (0001) plane was cleaned in UHV by heating to 400°C. GaSe was deposited from resistively heated Knudsen cells at T=300° C. After annealing at 450°C an epitaxial GaSe overlayer is formed as evidenced by X-ray diffraction, scanning tunneling microscopy, low energy electron diffraction and photoelectron spectroscopy.
Atomic Processes in Silicon Hetero-Epitaxy
Authors: Venables J.A. , Drucker J.S. , Raynerd G. 
Published: March 2011

ABSTRACTThe growth of metals and semiconductors on reconstructed semiconductor surfaces proceeds through a number of conceptually distinct stages. These include: 1) the growth of the first layer or layers, which may have different reconstructions as growth proceeds; 2) the growth of (2D or 3D) islands of the deposit, and/or by step flow; 3) coalescence and/or coarsening of islands and/or the introduction of defects such as dislocations. Of particular interest are cases when the different ‘stages’ are in competition with each other, i.e. they constitute alternative sinks for (and sources of) arriving and migrating adatoms. The development of rate equations to describe such situations, and extract relevant atomic parameters, is outlined. Experimental examples are taken from recent work on Ag and Ge deposits on Si( 111) and (100) surfaces.
Real-Time Femtosecond Ellipsometry of SixGe1−x Epilayers
Authors: Choo H. R. , Downer M. C. , Kesan V. P. 
Published: March 2011

ABSTRACTWe have developed a femtosecond ellipsometer by incorporating ellipsometric probe optics into a rapid scan femtosecond pump-and-probe experiment. The system allows near real-time display of the photo-induced reflectivity changes and provides complete characterization of the time-varying dielectric function. This ellipsometer is used ex situ to characterize the femtosecond response of relaxed, MBE-grown SixGe1−x alloys over the complete composition range. The results show. that the femtosecond response depends strongly on alloy composition in optically thick samples. Ge-like samples (x<0.37) show a characteristic two-component response which may be caused by intervalley L →Γ hole scattering and impact ionization. For a given alloy composition, the presence of interfacial strain or surface oxidation strongly alter the femtosecond response.
Crystal Structures of Epitaxially Grown Fe16N2 Single Crystal Films with Giant Magnetic Moments
Authors: Komuro Matahiro , Hoshiya Hiroyuki , Takahashi Hiroaki , Mitsuoka Katsuya , Sugita Yutaka 
Published: March 2011

ABSTRACTLattice parameters and crystal orientation for Fe1 6.N2 were determined by an X-ray diffraction method using a three axes goniometer. The lattice parameters of the a-axis and c-axis(a0, c0.) are 5.71 !A and 6.33 !A, respectively. The co corresponds to that of In0, 2,Gao.,s As substrates. Crystal orientation between Fe1 5.N2. films and Ino.,2Gao.,8 As is Fe1 0N2(001)//In0 2.Ga0.2 As(1001) and Fe1 0.N2.(100)//In02Ga0.6As(100). Intensity ratios for these diffraction peaks are in good agreement with calculated values proposed by Jack.
Molecular Beam Epitaxy Study of InAs/GaSb Heteroepitaxy on The (111)A and (111)B Orientations
Authors: Dura J. A. , Zborowski J. T. , Golding T. D. 
Published: March 2011

ABSTRACTWe have investigated the molecular beam epitaxial growth of homoepitaxial InAs and GaSb and InAs/GaSb heterostructures on both the (111)A and (111)B orientations. Our studies have found that high quality GaSb epilayers can be grown on both the (111)A and (111l)B orientations over a wide range of growth temperatures and flux ratios. Reflection high energy electron diffr-action phase diagrams for GaSb [111[ are presented. InAs/GaSb heterostructures, simultaneously grown on (11l)A and (111)B orientations, have been investigated by secondary ion mass spectroscopy depth profiles and double crystal x-ray diffraction. Unintentional incorporation of the ‘second’ group-V element is found to be approximately three times greater in the (111)A orientation than in the (111)B for both species.
Near Bandgap Optical Absorption Measurements on InGaAs/InP Strained Layers with Coarse Structure
Authors: Roura P. , Bosch J. , Cornet A. , Peiroi F. , Morante J.R. , Clark S. A. , Williams R.H. 
Published: March 2011

ABSTRACTOptical absorption measurements have been carried out on compressive InGaAs/FInP strained layers. It is shown that thoptical absorption analysis is a powerful technique in order to study the inhomogeneities of strained layers. The energetic dispersion of the heavy hole relative to the light hole subband σHH/σLH is related with the presence of the coarse structure seen in Transmission Electron Microscopy observations.
“Barrierless” Misfit Dislocation Nucleation in SiGe/Si Strained Layer Epitaxy
Authors: Perovic D.D. , Houghton D.C. 
Published: March 2011

ABSTRACTThe study of the critical thickness/strain phenomenon inherent in metastable, layered heterostructures has led to the development of several models which describe elastic strain relaxation. Hitherto, the nucleation of misfit dislocations required for coherency breakdown is the least well understood aspect of strain relaxation, due to the paucity of experimental data. Moreover, existing theoretical calculations predict relatively large activation energy barriers (>10 eV) for misfit dislocation nucleation in relatively low misfit (<2%) systems. In this work it will be shown that the nucleation of misfit dislocations can occur spontaneously demonstrating a vanishingly small activation energy barrier. Specifically, experimental studies of a wide range of GexSi1−x/Si (x< 0.5) hetero-structures, grown by MBE and CVD techniques, have provided quantitative data from bulk specimens on the observed misfit dislocation nucleation rate and activation energy using large-area diagnostic techniques (eg. chemical etching/Nomarski microscopy). In parallel, the strained layer microstructure was studied in detail using crosssectional and plan-view electron microscopy in order to identify a new dislocation nucleation mechanism, the ‘double half-loop’ source. From the combined macroscopic and microscopic analyses, a theoretical treatment has been developed based on nucleation stress and energy criteria which predicts a “barrierless” nucleation process exists even at low misfits (< 1%). Accordingly, the observed misfit dislocation nucleation event has been found both experimentally and theoretically to be rate-controlled solely by Peierls barrier dependent, glide-activated processes with activation energies of ∼2 eV.
Scanning Tunneung Microscope Studies of Initial Epitaxial Growth of YBa2Cu3O7-δ Thin Films
Authors: Zheng Xiang-Yang , Lowndes D. H. , Zhu Shen , Warmack R. J. 
Published: March 2011

ABSTRACTThe initial stages of epitaxial growth of laser ablated YBa2Cu3O7-δ (YBCO) thin films on (001) SrTiO3, LaAlO3, and MgO substrates, and on slightly miscut LaA1O3 and SrTiO3, have been studied with scanning tunneling microscopy (STM). Surface images show that the initial YBCO growth mode can be either of the Stranski- Krastanov or the Volmer-Weber type, depending on the film-substrate lattice mismatch and the growth temperature. A small substrate miscut angle is found to strongly influence the growth mode of YBCO films. Screw dislocation-mediated growth is suppressed, and films grown at 800°C on (001) LaAlO3 substrates with miscut angle of 2.0° along <100> or <110> directions were found to consist of tilted platelets that are epitaxially aligned with the substrate crystal lattice.
The Effect of Substrate Surface Orientation and Epilayer Thickness on Ingaas/Gaas Epilayer Tilt and Tilt Direction
Authors: Chang J.C.P. , Kavanagh K.L. 
Published: March 2011

ABSTRACTEpilayer tilt about an in-plane axis has been measured for a number of InGaAs/GaAs interfaces grown by solid source molecular beam epitaxy on (001) substrates cut nominally flat or cut 2 degrees towards the <010> or <111> direction. It is found that a much larger tilt develops in epilayers grown on off oriented wafers although a comparable degree of strain was relaxed. The tilt is a function of epilayer thickness for thicknesses exceeding a second critical thickness which we associate with the onset of relaxation by predominantly dislocation multiplication processes.
The Effect of The Initial Nucleation Temperature on The Misfit Dislocation Structure of InP-on-GaAs Heterostructures
Authors: Riesz Ferenc , Radnoczi G. , Pecz B. , Rakennus K. , Hakkarainen T. , Pesek A. , Lischka K. 
Published: March 2011

ABSTRACTThe misfit dislocation structure of vicinal InP-on-GaAs heterostructures is studied by transmission electron microscopy (TEM). An island type growth is identified. The misfit stress is not fully relaxed at the interface. X-ray measurements on strain relaxation and epilayer misorientation are also reported, and the latter results are explained with the asymmetric introduction of 6Ø° dislocations at island edges. Comparing the results, it is concluded that x-ray data supply additional, although indirect, information on initial growth which is hardly detectable by TEM.
A Model of Surface Misorientation Occurring During MBE of GaAs:Be
Authors: Bessolov V.N. , Lebedev M.V. 
Published: March 2011

ABSTRACTAn impurity adsorption model is proposed accounting for a distortion of the surface morphology of GaAs:Be epitaxial layers and an emergence of misoriented facets. According to the model, the morphology distortion occurs as the surface sublimation energy of the growing face drops down to zero because of adsorption of Be atoms at the layer surface. The model is in good agreement with available experimental data on the surface morphology distortion of GaAs:Be layers grown by MBE.
Low-Defect-Density Ge on Si for Large-Lattice-Mismatched Semiconductor Integration and Strain-Engineered Devices
Authors: Malta D.P. , Posthill J.B. , Enquist P.M. , Markunas R.J. , Humphreys T.P. , Parikh N.R. 
Published: March 2011

ABSTRACTHeteroepitaxial Ge layers were grown on vicinal Si(100) by molecular beam epitaxy (MBE) at substrate temperatures of 500°C and 900°C. The layers grown at 500°C were topographically smooth with planar interfaces and a typically high threading dislocation density at the surface (> 108cm−2). Layers grown at 900°C (nucleation at 500°C) showed smooth topography, an interface highly facetted on (111) planes and a dense network of dislocations that is well confined to the interfacial region. Etch pit density measurements indicated that defect densities at the surface were as low as 1 × 105cm−2. Biaxial tensile strains of 1.2 × l0−3 and 2.5 × l0−3 were measured by Raman spectroscopy for the 500°C and 900°C layers, respectively. RBS/channeling spectra supported crosssection TEM results indicating interfacial defect confinement in the layers grown at 900°C. A model describing thermal radiation absorption suggests that interfacial Ge melting occurred during the high temperature growths.