Molecular Beam Epitaxy (molecular + beam_epitaxy)

Distribution by Scientific Domains

Kinds of Molecular Beam Epitaxy

  • source molecular beam epitaxy


  • Selected Abstracts


    Interdiffusion phenomena in InGaAs/GaAs superlattice structures

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2010
    B. Sar, kavak
    Abstract We have studied structural properties of InGaAs/GaAs superlattice sample prepared by Molecular Beam Epitaxy (MBE) using high resolution X-ray diffractometer (HRXRD). Increasing strain relaxation and defect generations are observed with the increasing Rapid Thermal Annealing (RTA) temperature up to 775 C. The higher temperatures bring out relaxation mechanisms; interdiffusion and favored migration. The defect structure and the defects which are observed with the increasing annealing temperature were analyzed. Firstly, the in-plane and out-of-plane strains after the annealing of sample were found. Secondly, the structural defect properties such as the parallel X-ray strain, perpendicular X-ray strain, misfit, degree of relaxation, x composition, tilt angles and dislocation that are obtained from X-ray diffraction (XRD) analysis were carried out at every temperature. As a result, we observed that the asymmetric peaks especially in asymmetric (224) plane was affected more than symmetric and asymmetric planes with lower polar or inclination angles due to c-direction at low temperature. These structural properties exhibit different unfavorable behaviors for every reflection direction at the increasing temperatures. The reason is the relaxation which is caused by spatially inhomogeneous strain distribution with the increasing annealing temperature. In the InGaAs superlattice samples, this process enhances preferential migration of In atoms along the growth direction. Further increase in the annealing temperature leads to the deterioration of the abrupt interfaces in the superlattice and degradation in its structural properties. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Controlled Nucleation of GaN Nanowires Grown with Molecular Beam Epitaxy

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Kris A. Bertness
    Abstract The location of GaN nanowires is controlled with essentially perfect selectivity using patterned SiNx prior to molecular beam epitaxy growth. Nanowire growth is uniform within mask openings and absent on the mask surface for over 95% of the usable area of a 76 mm diameter substrate. The diameters of the resulting nanowires are controlled by the size of the mask openings. Openings of approximately 500 nm or less produce single nanowires with symmetrically faceted tips. [source]


    Epitaxial Graphene Growth by Carbon Molecular Beam Epitaxy (CMBE)

    ADVANCED MATERIALS, Issue 37 2010
    Jeongho Park
    A novel growth method (carbon molecular beam epitaxy (CMBE)) has been developed to produce high-quality and large-area epitaxial graphene. This method demonstrates significantly improved controllability of the graphene growth. CMBE with C60 produces AB stacked graphene, while growth with the graphite filament results in non-Bernal stacked graphene layers with a Dirac-like electronic structure, which is similar to graphene grown by thermal decomposition on SiC (000-1). [source]


    An Inorganic/Organic Semiconductor "Sandwich" Structure Grown by Molecular Beam Epitaxy

    ADVANCED MATERIALS, Issue 47 2009
    S. Blumstengel
    Preparation of ZnO/organic/ZnO "sandwich" semiconductor hybrid structures by molecular beam epitaxy is reported. Overgrowth of the organic layer becomes possible because ZnO epitaxy requires exceptionally low substrate temperatures. The molecule, a spirobifluorene derivative, withstands ZnO overgrowth without degradation of its optical properties. Excitonic coupling as well as optical gain in ZnO/organic/ZnO sandwich hybrid structures are demonstrated. [source]


    First step to Si photonics: synthesis of quantum dot light-emitters on GaP substrate by MBE

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2009
    Weiming Guo
    Abstract We have grown InAs and InP quantum dots (QDs) on GaP substrate by Molecular Beam Epitaxy (MBE) and analysed them by Atomic Force Microscopy (AFM) and photoluminescence (PL). AFM images confirm the formation of InAs and InP QDs. Largest InAs QDs density is obtained at a growth temperature of 450 C and under an AsH3 flux of 0.3SCCM. The evolution of QDs shape and absence of photoluminescence indicate a likely plastic relaxation of the strain between InAs and GaP. Concerning InP/GaP QDs, their lateral size, height and density indicate good quality QDs. Photoluminescence signal has been detected for capped InP/GaP QDs until 180 K. The unchanged peak position with respect to InP coverage is attributed to the nearly constant height of the QDs. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Reflectance-anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs (001)

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2008
    J. Ortega-Gallegos
    Abstract Reflectance-Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E1 optical transition as a probe. We follow the kinetics of the deposition of GaAs and In0.3Ga0.7As on GaAs (001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As4 or As2 flux pressure of 5 10,6 Torr. Clear RA-oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga-As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Interfacial spin structure in epitaxial Fe/FeSn2 bilayers with exchange bias

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004
    F. Stromberg
    Abstract Fe/FeSn2 structures with epitaxial FeSn2 layers have been grown by MBE (Molecular Beam Epitaxy). Exchange bias and pinning phenomena were proved by SQUID magnetometry. In order to elucidate the spin structure at the Fe/FeSn2 interface and in some depth of the FeSn2 layer with CEMS (Conversion Electron Mssbauer Spectroscopy), 57FeSn2 tracer layers of approx. 50 thickness have been incorpo- rated in the base structure, the only difference being the isotopic enrichment with 57Fe. An ellipsoidal model was applied to represent the spin structure. A strong out-of-plane component of the spin structure at the interface was observed. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Proceedings of the E-MRS 2003 Fall Meeting , Symposia A and C

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
    Marek Godlewski
    This volume contains the proceedings of Symposium A: Novel Wide Bandgap Materials for Optoelectronic and Electronic Applications and Symposium C: 5th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology at the E-MRS 2003 Fall Meeting, organized by the European Materials Research Society for the first time in Warsaw, Poland, 15,19 September 2003. Symposium A reviewed recent progress in the studies of wide bandgap materials such as nitrides and ZnO, as well as in relevant experimental techniques, whereas Symposium C was devoted to the current trends in physics and technology of MBE and MOCVD. [source]


    Three-dimensional ordering in self-organized (In,Ga)As quantum dot multilayer structures

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009
    V. Kladko
    Abstract Molecular beam epitaxy (MBE) grown In0.5Ga0.5As/GaAs multilayer structures with quantum dots chains (QDs), obtained under different growth conditions, were investigated by high-resolution X-ray diffractometry (HRXRD) and AFM. It was determined that self-organized epitaxial growth of In0.5Ga0.5As/GaAs can lead to the formation of three-dimensional quantum-dot crystals with triclinic (distorted cubic) unit cell. The mechanisms of QDs ordering in dependence on As flux are analyzed. [source]


    Controlled Ge quantum dots positioning with nano-patterned Si(001) substrates

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2006
    A. Bavard
    Abstract A square nanometric patterned substrate (period 20 nm) is obtained by direct twist bonding of two twin Si(001) surfaces, thinning and preferential chemical etching. Molecular beam epitaxy of Ge is carried out on a sample having heterogeneous trench depths to analyse islands positioning as a function of the surface morphology. Scanning electron microscopy observations show that small single dots per mesa or large dots covering several mesas can be observed. It highlights the influence of the mesa aspect ratio on the control of Ge islands self-organization, and suggests the occurrence of an effective activation barrier depending on the surface profile. The position-dependent energy stored in a dot for a given surface profile is estimated from a very simple model based on the balance between capillarity and elastic relaxation terms. By choosing a cycloid-like profile, experimental observations can be explained without fitting parameters. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    The impact of SiC substrate treatment on the heteroepitaxial growth of GaN by plasma assisted MBE

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005
    A. S. Brown
    Abstract We report on the impact of the preparation of the Si-face 4H-SiC(0001)Si substrate using a Ga flash-off process on the epitaxial growth of GaN by plasma-assisted molecular beam epitaxy. The nucleation, as well as the resultant structural and morphological properties of GaN grown directly on 4H-SiC(0001)Si are strongly influenced by the chemical and morphological modifications of the SiC surface induced by the Ga flash-off process. Herein we describe the impact of the specific concentration of Ga incident on the surface (quantified in terms of monolayer (ML) coverage): of 0.5 ML, 1ML and 2ML. The residual oxygen at the SiC surface, unintentional SiC nitridation and the formation of cubic GaN grains during the initial nucleation stage, are all reduced when a 2 ML Ga flash is used. All of the above factors result in structural improvement of the GaN epitaxial layers. The correlation between the SiC surface modification, the initial nucleation stage, and the GaN epitaxial layer structural quality has been articulated using x-ray photoelectron spectroscopy, x-ray diffraction, atomic force microscopy and spectroscopic ellipsometry data. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    A comparative study for profiling ultrathin boron layers in Si

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2003
    E. Basaran
    Abstract The carrier concentration-depth profiles of ultrathin boron layers in Si, grown by molecular beam epitaxy, are determined by the electrochemical capacitance-voltage (ECV) and the spreading resistance (SR) profiling techniques. Secondary ion mass spectrometry (SIMS) is employed as a base for the comparison of the results. It has been shown that, under carefully chosen conditions, both ECV and SR techniques are able to resolve ultrathin layers including a delta layer, however ECV match better with the results of SIMS than that of SR. ( 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Nano vanadyl-phthalocyanine crystals fabricated on KBr substrate

    ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2008
    Suguru Mototani
    Abstract Vanadyl-phthalocyanine (VOPc) thin films deposited on a KBr substrate by molecular beam epitaxy (MBE) consist of nano-VOPc crystals epitaxially grown. The nano-VOPc crystals acquire a square shape as a result of annealing at 150C. The size of the nano-crystals is controllable by changing the conditions of MBE deposition and thermal treatment. The growth processes of nano-crystals on the KBr substrate are elucidated experimentally and are shown to be closely related to strong interaction between the VOPc molecules and the KBr substrate. Their mechanisms can be explained in terms of surface diffusion of the VOPc molecules on the KBr substrate. 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 41,48, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20645 [source]


    Epitaxial Graphene Growth by Carbon Molecular Beam Epitaxy (CMBE)

    ADVANCED MATERIALS, Issue 37 2010
    Jeongho Park
    A novel growth method (carbon molecular beam epitaxy (CMBE)) has been developed to produce high-quality and large-area epitaxial graphene. This method demonstrates significantly improved controllability of the graphene growth. CMBE with C60 produces AB stacked graphene, while growth with the graphite filament results in non-Bernal stacked graphene layers with a Dirac-like electronic structure, which is similar to graphene grown by thermal decomposition on SiC (000-1). [source]


    An Inorganic/Organic Semiconductor "Sandwich" Structure Grown by Molecular Beam Epitaxy

    ADVANCED MATERIALS, Issue 47 2009
    S. Blumstengel
    Preparation of ZnO/organic/ZnO "sandwich" semiconductor hybrid structures by molecular beam epitaxy is reported. Overgrowth of the organic layer becomes possible because ZnO epitaxy requires exceptionally low substrate temperatures. The molecule, a spirobifluorene derivative, withstands ZnO overgrowth without degradation of its optical properties. Excitonic coupling as well as optical gain in ZnO/organic/ZnO sandwich hybrid structures are demonstrated. [source]


    Self-Assembled Pb Nanostructures on Si(111) Surfaces: From Nanowires to Nanorings

    ADVANCED MATERIALS, Issue 45 2009
    Rui Wu
    Abstract A template-directed growth method for metals is described in which ordered arrays of super-long single-crystalline metal nanowires with atomic-level-controlled width, thickness (height), and surface location are prepared by molecular beam epitaxy. Their subsequent examination by in situ scanning tunneling microscopy is also outlined. A phase-separated stripe pattern composed of alternately a Ge-rich incommensurate phase and a ,3,,,3 phase is first obtained by Ge deposition on Si(111) substrates. Further deposition of Pb on this patterned surface leads to a well-ordered array of super-long Pb nanowires. Using the same mechanism, superconducting Pb nanorings can also be fabricated. In this review of our recent work, these Pb single-crystalline nanowires and nanorings are shown to serve as an ideal platform for the study of superconductivity in reduced dimensionalities. Furthermore, because the widths and spatial distributions of two phases can be precisely controlled by the Ge coverage and substrate temperature, and because a metal will always selectively nucleate on one of two phases, this template-directed growth method can be applied to a wide range of metals. [source]


    Controlled Growth of High-Quality ZnO-Based Films and Fabrication of Visible-Blind and Solar-Blind Ultra-Violet Detectors

    ADVANCED MATERIALS, Issue 45 2009
    Xiaolong Du
    Abstract ZnO is a wide-bandgap (3.37,eV at room temperature) oxide semiconductor that is attractive for its great potential in short-wavelength optoelectronic devices, in which high quality films and heterostructures are essential for high performance. In this study, controlled growth of ZnO-based thin films and heterostructures by molecular beam epitaxy (MBE) is demonstrated on different substrates with emphasis on interface engineering. It is revealed that ultrathin AlN or MgO interfacial layers play a key role in establishing structural and chemical compatibility between ZnO and substrates. Furthermore, a quasi-homo buffer is introduced prior to growth of a wurtzite MgZnO epilayer to suppress the phase segregation of rock-salt MgO, achieving wide-range bandgap tuning from 3.3 to 4.55,eV. Finally, a visible-blind UV detector exploiting a double heterojunction of n-ZnO/insulator-MgO/p-Si and a solar-blind UV detector using MgZnO as an active layer are fabricated by using the growth techniques discussed here. [source]


    High-resolution three-dimensional reciprocal-space mapping of InAs nanowires

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2009
    S. O. Mariager
    Grazing-incidence X-ray diffraction is combined with a two-dimensional pixel detector to obtain three-dimensional reciprocal-space maps of InAs nanowires grown by molecular beam epitaxy. This rapid data-acquisition technique and the necessary correction factors are described in general terms, as well as for the specific setup used, for which a resolution of ,2 10,3, is computed. The three-dimensional data sets are obtained by calculating the reciprocal space coordinates for every pixel in the detected images, and are used to map the diffuse scattering from the nanowires as both two-dimensional reciprocal-space maps and three-dimensional isosurfaces. The InAs nanowires are shown to consist mainly of wurtzite crystal with a c/a ratio of 1.641. The diffuse scattering reveals two different facet structures, both resulting in hexagonal cross sections of the nanowires. [source]


    Structure of the (110) antiphase boundary in gallium phosphide

    JOURNAL OF MICROSCOPY, Issue 2 2002
    D. Cohen
    Summary The morphology of antiphase boundaries in GaP films grown by molecular beam epitaxy on Si (001) has been studied by transmission electron microscopy. The inversion of the crystal polarity between antiphase domains was confirmed by convergent-beam electron diffraction. The APBs were often found to facet parallel to {110} planes. Strong-beam ,-fringe contrast observed along the (110) facets indicates that adjacent antiphase domains are related by an additional rigid-body lattice translation. Diffraction-contrast analysis shows that this R corresponds to a shear parallel to the [001] direction and a small expansion. The magnitude of the translation was inferred, quantitatively, through a comparison between energy-filtered zero-loss images of the ,-fringe contrast with numerical calculations. The components of the rigid-body lattice translation were determined to be 0.023 0.0033 nm in the [001] direction and 0.005 0.002 nm in the 0 direction. Based upon a geometric model of the {110} antiphase boundary, the lengths of the Ga and P antisite bonds were calculated to be 254 2 pm and 227 4 pm, respectively. [source]


    Photoluminescence properties of GaAs nanowire ensembles with zincblende and wurtzite crystal structure

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
    B. V. Novikov
    Abstract Self-standing III,V nanowires (NWs) are promising building blocks for future optoelectronic devices such as LEDs, lasers, photodetectors and solar cells. In this work, we present the results of low temperature photoluminescence (PL) characterization of GaAs NWs grown by Au-assisted molecular beam epitaxy (MBE), coupled with the transmission electron microscopy (TEM) structural analysis. PL spectra contain exci- ton peaks from zincblende (ZB) and wurtzite (WZ) crystal structures of GaAs. The peaks are influenced by the quantum confinement effects. PL bands corresponding to the exciton emission from ZB and WZ crystal phases are identified, relating to the PL peaks at 1.519 eV and 1.478 eV, respectively. The obtained red shift of 41 meV for WZ GaAs should persist in thin NWs as well as in bulk materials. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Highly conductive and optically transparent GZO films grown under metal-rich conditions by plasma assisted MBE

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3-4 2010
    H. Y. Liu
    Abstract We demonstrate a critical effect of a metal-to-oxygen ratio on the electrical, optical, and structural properties of ZnO films heavily doped with Ga (carrier concentration in the range of 1020,1021 cm,3) grown by plasma-assisted molecular beam epitaxy. The as-grown layers prepared under the metal-rich conditions exhibited resistivities below 3 10,4 , cm and an optical transparency exceeding 90% in the visible spectral range as well as a large blue shift of the transmission/absorption edge attributed to the Burstein,Moss shift of the Fermi level deep into the conduction band, indicating high donor concentration. In contrast, the films grown under the oxygen-rich conditions required thermal activation and showed inferior properties. Furthermore, electrical measurements point to the nonuniform depth distribution of free carriers. An oxygen-pressure-dependent surface disordering is suggested to be responsible for the drastic effect of the metal-to-oxygen ratio on the film properties. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Critical diameters and temperature domains for MBE growth of III,V nanowires on lattice mismatched substrates

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 4 2009
    G. E. Cirlin
    Abstract We report on the growth properties of InAs, InP and GaAs nanowires (NWs) on different lattice mismatched substrates, in particular, on Si(111), during Au-assisted molecular beam epitaxy (MBE). We show that the critical diameter for the epitaxial growth of dislocation-free III,V NWs decreases as the lattice mismatch increases and equals 24 nm for InAs NWs on Si(111), 39 nm for InP NWs on Si(111), 44 nm for InAs NWs on GaAs(111)B, and 110 nm for GaAs NWs on Si(111). When the diameters exceed these critical values, the NWs are dislocated or do not grow at all. The corresponding temperature domains for NW growth extend from 320 C to 340 C for InAs NWs on Si(111), 330 C to 360 C for InP NWs on Si(111), 370 C to 420 C for InAs NWs on GaAs(111)B and 380 C to 540 C for GaAs NWs on Si(111). Experimental values for critical diameters are compared to the previous findings and are discussed within the frame of a theoretical model. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Electronic structure of GaN(0001)-2 2 thin films grown by PAMBE

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2008
    R. Gutt
    Abstract Gallium nitride thin films were grown on silicon carbide (0001) by plasma-assisted molecular beam epitaxy (PAMBE). The samples were cooled down in nitrogen plasma and characterized in situ by reflection high energy electron diffraction (RHEED), photoelectron spectroscopy (XPS/UPS), and atomic force microscopy (AFM) revealing stoichiometric and smooth GaN films virtually free of contaminations. We present valence band data obtained by UPS with strong emission from surface states inside the fundamental band gap. These states and the observed 2 2 surface reconstruction are highly sensitive towards residual molecules. Once these surface states have disappeared the original state could not be recovered by surface preparation methods underlining the necessity of in situ investigations on as-grown surfaces. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Surface morphology of highly mismatched InSb films grown on GaAs substrates by molecular beam epitaxy

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 2 2007
    Min Xiong
    Abstract InSb films on GaAs(001) substrates with and without GaAs buffer layer have been grown by molecular beam epitaxy. Rather than surface undulations, aligned ripples and pyramidal hillocks along the orthogonal ,110, directions were observed on the surface of InSb films. Both the preferential growth and the termination of ripples were proved to be related to strain-driven mass transport. A model was proposed to elucidate the formation of the hillocks, which are more efficient to relax strain than ripples. Due to the strain relaxation through hillocks with small bases predominantly, the surfaces of the InSb films grown without a GaAs buffer layer are smoother than those of films grown with a GaAs buffer layer. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Optical anisotropy of A - and M -plane InN grown on free-standing GaN substrates

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010
    P. Schley
    Abstract Wurtzite A - and M -plane InN films were grown by molecular beam epitaxy (MBE) on free-standing GaN substrates. Spectroscopic ellipsometry (SE) in the photon energy range from 0.56 up to 15,eV was applied in order to determine the ordinary and extraordinary complex dielectric function (DF) of InN. A distinct optical anisotropy was found over the whole energy range. The extraordinary absorption edge in comparison to the ordinary one is shifted to higher energies confirming previous studies. The investigations in the upper vacuum-ultraviolet (VUV) spectral range (9.5,15,eV) yielded transition energies for four critical points (CPs) of the band structure (BS) which have not been observed so far. [source]


    Optical properties of InN grown on Si(111) substrate

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010
    E. Sakalauskas
    Abstract A comprehensive characterization of the optical properties of wurtzite InN films grown by molecular beam epitaxy on Si(111) substrates is presented. Two types of films are investigated in this work: InN on AlN/Si(111) and InN on GaN/AlN/Si(111). Their properties are compared to a layer deposited on GaN/sapphire substrate. The dielectric function (DF) is obtained from spectroscopic ellipsometry (SE). The infrared studies yield the plasma frequency and thus the electron density, while the interband absorption is probed between 0.56 and 9.8,eV. For InN grown on Si(111) substrate, the absorption onset is slightly shifted to higher energies with respect to the InN film grown on GaN/sapphire which can be attributed to higher electron concentrations. Despite this, strongly pronounced optical transitions due to critical points of the band structure are found in the high-energy part of the DF. It emphasizes the already promising quality of the InN films on silicon. Band-gap renormalization (BGR), band filling, and strain are taken into account in order to estimate the intrinsic band gap of wurtzite InN. For the InN layers on silicon, we get a band gap between 0.66 and 0.685,eV. [source]


    Strain relaxation in AlN/GaN heterostructures grown by molecular beam epitaxy

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008
    G. P. Dimitrakopulos
    Abstract The strain distribution and defects in a graded AlN/GaN heterostructure comprising AlN layers from 3 nm up to 100 nm grown by plasma-assisted MBE were studied using transmission electron microscopy techniques. Gradual strain relaxation was observed as well as strain partitioning between the GaN spacers and the thicker AlN layers. Elastic strain is retained even in the thicker layers of the heterostructure. Extensive introduction of threading and misfit dislocations is observed at and above the 7 nm AlN layer. The threading dislocations adopt inclined zig-zag line directions thus contributing to the relief of alternating compressive-tensile elastic strain across the the layers of the heterostructure. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Interdiffusion in SiGe alloys with Ge contents of 25% and 50% studied by X-ray reflectivity

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008
    M. Medun
    Abstract The interdiffusion in SiGe alloys has been studied by X-ray specular reflectivity using ex-situ and in-situ annealing experiments. We report on the evolution of the Ge profile of strain-compensated Si/SiGe multilayers due to high temperature annealing. These multilayers were grown pseudomorphically and strain-symmetrized on relaxed Si0.75Ge0.25 and Si0.5Ge0.5 pseudosubstrates by molecular beam epitaxy at 330 C. The multilayer structures were annealed at several temperatures around 590 C and around 800 C. From modelling the X-ray specular reflectivity scans at various stages of the interdiffused structures, we obtained interdiffusion coefficients resulting in the activation energy and the prefactor for interdiffusion corresponding to Si0.75Ge0.25 and Si0.5Ge0.5. The results obtained ex-situ for Si0.5Ge0.5 and in-situ for Si0.75Ge0.25 provide accurate values of diffusion parameters. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Hall effect anomalies in n-type Pb1,xEux Se layers grown on silicon

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2007
    A. Almaggoussi
    Abstract Transport measurements (resistivity and Hall density) were made in the temperature range 10,300 K on n-Pb1,xEux Se (0 , x , 8%) epilayers grown by molecular beam epitaxy on silicon substrates. In the vicinity of 77 K anomalies of electron concentration were observed. To explain this anomalous behaviour, a model is proposed based on the existence of three levels: two donors and one acceptor. The origin of these levels is attributed to native defects. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Application of microsize light-emitting diode structure for monolithic optoelectronic integrated circuits

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007
    S. Y. Moon
    Abstract A Si/III,V,N alloys/Si structure was grown on a Si substrate by solid-source molecular beam epitaxy (SSMBE) with an rf plasma nitrogen source and electron-beam (EB) evaporator. A two-dimensional (2D) growth mode was maintained during the growth of all layers. High-resolution X-ray diffraction (HRXRD) revealed that the structure had a small lattice mismatch to the Si substrate. InGaPN/GaPN double-heterostructure (DH) light-emitting diodes (LEDs) were fabricated on Si/III,V,N alloys/Si structure. The various sized LEDs were fabricated to put into the MOSFET for monolithic optoelectronic integrated circuits (OEIC). The luminescence properties of LEDs were evaluated by electroluminescence (EL). A double emission peak from all LED samples was observed at about 642 nm and 695 nm at room temperature (RT). As injection current increased, the emission peak wavelength changed from the peak wavelength of the InGaPN layer to that of the GaPN layer, likely due to carrier overflow of the active layer. A simplified fabrication process for the microsize LED of the unit circuit was proposed. The LEDs with emission areas from 5 5 ,m2 to 20 20 ,m2 were fabricated. The LED with an emission area of 5 5 ,m2 can be applied to an optical device of a monolithic OEIC. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]