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Showing papers on "Epitaxy published in 2005"


Journal ArticleDOI
TL;DR: It is suggested that the interplay of the liquid-solid interfacial energy with the silicon surface energy expressed in terms of an edge tension is responsible for the change of the growth direction.
Abstract: We found that silicon nanowires grown epitaxially on Si (100) via the vapor−liquid−solid growth mechanism change their growth direction from 〈111〉 to 〈110〉 at a crossover diameter of approximately 20 nm. A model is proposed for the explanation of this phenomenon. We suggest that the interplay of the liquid−solid interfacial energy with the silicon surface energy expressed in terms of an edge tension is responsible for the change of the growth direction. The value of the edge tension is estimated by the product of the interfacial thickness with the surface energy of silicon. For large diameters, the direction with the lowest interfacial energy is dominant, whereas for small diameters the surface energy of the silicon nanowire determines the preferential growth direction.

494 citations


Journal ArticleDOI
TL;DR: In this paper, the fabrication of GaAs hexagonal nanowires surrounded by vertical facets on a GaAs (111) B substrate using selective-area (SA) metalorganic vapor-phase epitaxial (MOVPE) growth was described.
Abstract: We report on the fabrication of GaAs hexagonal nanowires surrounded by {110} vertical facets on a GaAs (111) B substrate using selective-area (SA) metalorganic vapor-phase epitaxial (MOVPE) growth. The substrate for SA growth was partially covered with thin SiO2, and a circular mask opening with a diameter d0 of 50–200 nm was defined. After SA-MOVPE, GaAs nanowires with a typical diameter d ranging from 50 to 200 nm and a height from 2 to 9μm were formed vertically on the substrate without any catalysts. The size of the nanowire depends on the growth conditions and the opening size of the masked substrate. A possible growth mechanism is also discussed.

280 citations


Journal ArticleDOI
TL;DR: In this paper, the structure and composition of the metallic particles were analyzed by transmission electron microscopy and energy dispersive x-ray spectroscopy, and three different metallic compounds were identified: the hexagonal β′Au7Ga2 structure, the orthorhombic AuGa structure, and an almost pure Au face centered cubic structure.
Abstract: GaAs nanowires were grown by molecular-beam epitaxy on (111)B oriented surfaces, after the deposition of Au nanoparticles. Different growth durations and different growth terminations were tested. After the growth of the nanowires, the structure and the composition of the metallic particles were analyzed by transmission electron microscopy and energy dispersive x-ray spectroscopy. We identified three different metallic compounds: the hexagonal β′Au7Ga2 structure, the orthorhombic AuGa structure, and an almost pure Au face centered cubic structure. We explain how these different solid phases are related to the growth history of the samples. It is concluded that during the wire growth, the metallic particles are liquid, in agreement with the generally accepted vapor-liquid-solid mechanism. In addition, the analysis of the wire morphology indicates that Ga adatoms migrate along the wire sidewalls with a mean length of about 3μm.

271 citations


Journal ArticleDOI
TL;DR: In this paper, planar semipolar gallium nitride films were grown by hydride vapor phase epitaxy on sapphire, and they were determined to have N-face sense polarity and a threading dislocation density of 9×108 cm-2.
Abstract: Specular, planar semipolar gallium nitride films were grown by hydride vapor phase epitaxy. Planar films of (1013) and (1122) GaN have been grown on (1010) m-plane sapphire. The in-plane epitaxial relationship for (1013) GaN was [3032]GaN ∥[1210]sapphire and [1210]GaN ∥[0001]sapphire. The in-plane epitaxial relationship for (1122) GaN was [1121]GaN ∥[0001]sapphire and [1100]GaN ∥[1210]sapphire. The (1013) films were determined to have N-face sense polarity and a threading dislocation density of 9×108 cm-2. The (1122) films have Ga-face sense polarity and have a threading dislocation density of 2×1010 cm-2. The basal plane stacking fault density was 2 ×105 cm-1 for both orientations. The RMS roughness of the films was under 10 nm for a 5 ×5 µm2 area.

227 citations


Journal ArticleDOI
TL;DR: A mass transport model based on surface diffusion for metal-particle-assisted nanowire growth is presented and it is demonstrated that the Gibbs-Thomson effect can be neglected for III/V nanowires grown at conventional temperatures and pressures.
Abstract: We present a mass transport model based on surface diffusion for metal-particle-assisted nanowire growth. The model explains the common observation that for III/V materials thinner nanowires are longer than thicker ones. We have grown GaP nanowires by metal-organic vapor phase epitaxy and compared our model calculations with the experimental nanowire lengths and radii. Moreover, we demonstrate that the Gibbs-Thomson effect can be neglected for III/V nanowires grown at conventional temperatures and pressures.

224 citations


Journal ArticleDOI
TL;DR: In this article, photoluminescence spectra were obtained from completely dopant-activated samples with hole concentrations above 1.0×1018cm−3 and acceptor binding energy of 0.14 eV.
Abstract: We investigated photoluminescence (PL) from reliable and reproducible Sb-doped p-type ZnO films grown on n-Si (100) by molecular-beam epitaxy. Well-resolved PL spectra were obtained from completely dopant-activated samples with hole concentrations above 1.0×1018cm−3. From free electron to acceptor transitions, acceptor binding energy of 0.14 eV is determined, which is in good agreement with analytical results of the temperature-dependent PL measurements. Another broad peak at 3.050 eV, which shifts to lower energy at higher temperatures, indicates the formation of deep acceptor level bands related to Zn vacancies, which are created by Sb doping.

209 citations


Patent
Yosuke Shimamune1, Akira Katakami1, Akiyoshi Hatada1, Masashi Shima1, Naoyoshi Tamura1 
18 Apr 2005
TL;DR: In this article, a gate electrode is formed on a silicon substrate via a gate insulation film in correspondence to a channel region, source and drain regions of a p-type diffusion region formed in the silicon substrate at respective outer sides of sidewall insulation films of the gate electrode.
Abstract: A semiconductor device includes a gate electrode formed on a silicon substrate via a gate insulation film in correspondence to a channel region, source and drain regions of a p-type diffusion region formed in the silicon substrate at respective outer sides of sidewall insulation films of the gate electrode, and a pair of SiGe mixed crystal regions formed in the silicon substrate at respective outer sides of the sidewall insulation films in epitaxial relationship to the silicon substrate, the SiGe mixed crystal regions being defined by respective sidewall surfaces facing with each other, wherein, in each of the SiGe mixed crystal regions, the sidewall surface is defined by a plurality of facets forming respective, mutually different angles with respect to a principal surface of the silicon substrate.

206 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the practical advantages of pulsed laser deposition and currently accomplished intrinsic properties of ZnO films according to the abundant literature, and conclude that the PLD technique and related technologies have now mature to meet the requirements for fabricating UV-LEDs.
Abstract: The pulsed laser deposition (PLD) technique has been applied for the epitaxial growth of ZnO for more than two decades. The emergence of high-temperature stability of the excitonic lasing was first demonstrated in a microcrystalline ZnO film grown by PLD leading to recent remarkable growth in this field. A number of attempts have been made to improve the crystallinity for realizing p-type materials in the quest for ZnO-based short wavelength light emitting devices (LEDs). In this paper, we describe practical advantages of PLD and currently accomplished intrinsic properties of ZnO films according to the abundant literature. We find that correlation between Hall mobility and lateral grain size captures the effect of grain boundaries for the films grown on sapphire substrates. On the other hand, advantages of the use of lattice-matched ScAlMgO4 substrate are evidenced by the lower residual electron density, higher mobility and sharper exciton peaks in the photoluminescence and absorption spectra. We also focus on the wide-band-gap ternary alloy, MgxZn1−xO, especially in terms of the composition dependence of its lattice parameters and band-gap in two different crystallographic phases, to discuss the stability of this metastable compound. The studies on the PLD growth of multilayer and superlattices are briefly reviewed. We finally present the current capability of electron and hole doping by incorporating Ga and N into films grown on (0001) ScAlMgO4 substrates. We conclude that the PLD technique and related technologies have now mature to meet the requirements for fabricating UV-LEDs.

199 citations


Journal ArticleDOI
TL;DR: In this paper, high-resolution electron microscopy has been applied for studying lattice defects in nonpolar a-plane GaN grown on a 4H-SiC substrate with an AlN buffer layer.
Abstract: Conventional and high resolution electron microscopy havebeen applied for studying lattice defects in nonpolar a-plane GaN grownon a 4H-SiC substrate with an AlN buffer layer. Samples in plan-view andcross-section configurations have been investigated. Basal and prismaticstacking faults together with Frank and Shockley partial dislocationswere found to be the main defects in the GaN layers. High resolutionelectron microscopy in combination with image simulation supported Drum smodel for the prismatic stacking faults. The density of basal stackingfaults was measured to be ~;1.6_106cm-1. The densities of partialdislocations terminating I1 and I2 types of intrinsic basal stackingfaults were ~;4.0_1010cm-2 and ~;0.4_1010cm-2, respectively. The energyof the I2 stacking fault in GaN was estimated to be (40+-4) erg/cm2 basedon the separation of Shockley partial dislocations. To the best of ourknowledge, the theoretically predicted I3 basal stacking fault in GaN wasobserved experimentally for the first time.

198 citations


Journal ArticleDOI
TL;DR: In this paper, GaAs∕AlGaAs core-shell nanowires were fabricated by using selective area metalorganic vapor phase epitaxy (SVAE) by selectively growing on partially masked GaAs (111)B substrates.
Abstract: We fabricated GaAs∕AlGaAs core-shell nanowires by using selective-area metalorganic vapor phase epitaxy. First, GaAs nanowires were selectively grown on partially masked GaAs (111)B substrates; then AlGaAs was grown to form freestanding heterostructured nanowires. Investigation of nanowire diameter as a function of AlGaAs growth time suggested that the AlGaAs was grown on the sidewalls of the GaAs nanowires, forming GaAs∕AlGaAs core-shell structures. Microphotoluminescence measurements of GaAs and GaAs∕AlGaAs core-shell nanowires reveal an enhancement of photoluminescence intensity in GaAs∕AlGaAs core-shell structures. Based on these core-shell nanowires, AlGaAs nanotubes were formed by using anisotropic dry etching and wet chemical preferential etching to confirm the formation of a core-shell structure and to explore a new class of materials.

195 citations


Patent
10 May 2005
TL;DR: In this paper, a substrate is exposed to at least two different process gases to deposit one layer on top of another layer, and the next process gas contains silane and an etchant.
Abstract: Embodiments of the invention provide processes to deposit silicon-containing materials, such as selectively depositing an epitaxial silicon-germanium material containing a high dopant concentration. In one example, a substrate is exposed to at least two different process gases to deposit one layer on top of another layer. One process gas contains dichlorosilane, a germanium source and an etchant while the next process gas contains silane and an etchant. In other examples, a process gas contains dichlorosilane, methylsilane and hydrogen chloride or silane, methylsilane and hydrogen chloride. In one aspect, a deposited layer has interstitial sites within a crystalline lattice and contains about 3 at% or less of carbon within the interstitial sites and is subsequently annealed to incorporate carbon within substitutional sites of the crystalline lattice. In another aspect, a silicon-germanium stack has first, second and third layers containing germanium concentrations of about 25 at% or less, about 25 at% or more and about 5 at% or less.

Patent
31 May 2005
TL;DR: In this article, a method of growing highly planar, fully transparent and specular m-plane gallium nitride (GaN) films is proposed for a significant reduction in structural defect densities via a lateral overgrowth technique.
Abstract: A method of growing highly planar, fully transparent and specular m-plane gallium nitride (GaN) films. The method provides for a significant reduction in structural defect densities via a lateral overgrowth technique. High quality, uniform, thick m-plane GaN films are produced for use as substrates for polarization-free device growth.

Journal ArticleDOI
TL;DR: The direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case.
Abstract: Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called “self-catalysis” schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and “tree-like” morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires dir...

Journal ArticleDOI
TL;DR: In this paper, the As 4 flux intensity during the crystallization of Ga droplets into GaAs is changed, resulting in the shape control from dot to ring, which exhibits clear photoluminescence emission up to room temperature.

Book
01 Aug 2005
TL;DR: Schubert et al. as mentioned in this paper proposed a delta-like confinement of impurities in GaAs and showed that delta-doped GaAs can be used for delta-enhanced III-V semiconductors.
Abstract: Part I: 1. Introduction E. F. Schubert Part II: 2. Electronic structure of delta-doped semiconductors C. R. Proetto Part III: 3. Recent progress in delta-like confinement of impurities in GaAs K. H. Ploog 4. Flow-rate modulation epitaxy (FME) of III-V semiconductors T. Makimoto and Y. Horikoshi 5. Gas source molecular beam epitaxy (MBE) of delta-doped III-V semiconductors D. Ritter 6. Solid phase epitaxy for delta-doping in silicon I. Eisele 7. Low temperature MBE of silicon H.-J. Gossmann Part IV: 8. Secondary ion mass spectrometry of delta-doped semiconductors H. S. Luftmann 9. Capacitance-voltage profiling E. F. Schubert 10. Redistribution of impurities in III-V semiconductors E. F. Schubert 11. Dopant diffusion and segregation in delta-doped silicon films H.-J. Gossmann 12. Characterisation of silicon and delta-doped structures in GaAs R. C. Newman 13. The DX-center in silicon delta-doped GaAs and AlxGa1-xAs P. M. Koenraad Part V: 14. Luminescence and ellipsometry spectroscopy H. Yao and E. F. Schubert 15. Photoluminescence and Raman spectroscopy of single delta-doped III-V semiconductor heterostructures J. Wagner and D. Richards 16. Electron transport in delta-doped quantum wells W. T. Masselink 17. Electron mobility in delta-doped layers P. M. Koenraad 18. Hot electrons in delta-doped GaAs M. Asche 19. Ordered delta-doping R. L. Headrick, L. C. Feldman and B. E. Weir Part IV: 20. Delta-doped channel III-V field effect transistors (FETs) W.-P. Hong 21. Selectively doped heterostructure devices E. F. Schubert 22. Silicon atomic layer doping FET K. Nakagawa and K. Yamaguchi 23. Planar doped barrier devices R. J. Malik 24. Silicon interband and intersubband photodetectors I. Eisele 25. Doping superlattice devices E. F. Schubert.

Journal ArticleDOI
TL;DR: In this article, C60-based n-channel organic field effect transistors with mobility in the range of 4-1-cm2-V−1-s−1 were presented.

Journal ArticleDOI
TL;DR: In this article, a multilayer thin films consisting of titanium nitride (TiN) and silicon nitride(SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers.
Abstract: Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers u ...

Journal ArticleDOI
TL;DR: A method that does not require deposition and transforms a nanoscale layer of a complex crystalline compound into a new material using low-energy ion-beam preferential etching (IBPE) is reported, implying wide potential applicability to fabrication of other nanolayers.
Abstract: Developing fabrication methods for electronically active nanostructures is an important challenge of modern science and technology. Fabrication efforts1,2,3,4 for crystalline materials have been focused on state-of-the-art epitaxial growth techniques. These techniques are based on deposition of precisely controlled combinations of various materials on a heated substrate. We report a method that does not require deposition and transforms a nanoscale layer of a complex crystalline compound into a new material using low-energy ion-beam preferential etching (IBPE). We demonstrate this method by transforming a widely used5,6,7,8,9,10 insulator model system, SrTiO3, into a transparent conductor. Most significantly, the resistivity decreases with decreasing temperature as ∼T2.5±0.3 and eventually falls below that of room-temperature copper. These transport measurements imply a crystal quality in the conduction channel comparable to that obtained1 with the highest-quality growth techniques. The universality of low-energy IBPE implies wide potential applicability to fabrication of other nanolayers.

Journal ArticleDOI
TL;DR: In this article, the critical thickness for cracking was increased to at least 2 μ m by introducing a thick, graded AlGaN buffer layer, which provided a reliable diffusion barrier to avoid meltback etching.

Journal ArticleDOI
TL;DR: In this paper, the growth of epitaxial molybdenum oxide (MoOx,2
Abstract: We report the growth of epitaxial molybdenum oxide (MoOx,2

Journal ArticleDOI
TL;DR: In this paper, the growth of AlN buffer layer was studied, and the full width at half maximum (FWHM) of the AlN (0002) peak was smaller than that grown on Si (100) substrates.
Abstract: GaN has shown great potential for high-power high-frequency electronic devices and short-wavelength optical devices. To integrate GaN-based optoelectronic devices with Si-based electronic devices and reduce the cost, it is desirable to grow epitaxial GaN thin films and device structures on the Si substrate. However, a proper buffer layer is essential for epitaxial growth of GaN films on Si substrate due to large mismatch between them in the area of lattice constant, thermal expansion coefficient and chemistry feature. In the present work, the growth of AlN buffer layer was studied. Wurtzite aluminum nitride thin films were grown on Si (111) and Si (100) substrates using reactive sputtering deposition under different discharge powers. X-ray diffraction (XRD) patterns showed that full width at half maximum (FWHM) of AlN (0002) peak grown on Si (111) substrates was smaller than that grown on Si (100) substrates. Vibrational characterization by Fourier transform infrared spectroscopy (FTIR) revealed that the stress in the AlN films deposited on Si (111) substrates was also smaller than that deposited on Si (100) substrates. For Si (100) substrates, the large lattice mismatch between AlN (0001) and Si (100) is a main contribution to the large strain in the formed films. For Si (111) substrates, the strain in the films deposited on Si (111) largely depends on the discharge power in sputtering, and the strain due to defects and thermal mismatch contributes largely to the residual strain in the deposited films.

Patent
28 Nov 2005
TL;DR: In this paper, a method of epitaxially forming a silicon-containing material on a substrate surface is presented which includes positioning a substrate into a process chamber, where the substrate is exposed to a deposition gas to deposit an epitaxial layer on the monocrystalline surface and a polycrystalline layer on a second surface.
Abstract: In one example, a method of epitaxially forming a silicon-containing material on a substrate surface is presented which includes positioning a substrate into a process chamber. The substrate has a monocrystalline surface and at least a second surface, such as an amorphous surface and/or a polycrystalline surface. The substrate is exposed to a deposition gas to deposit an epitaxial layer on the monocrystalline surface and a polycrystalline layer on the second surface. The deposition gas preferably contains a silicon source and at least a second elemental source, such as a germanium source, a carbon source and/or combinations thereof. Thereafter, the method further provides exposing the substrate to an etchant gas to etch the polycrystalline layer and the epitaxial layer in a manner such that the polycrystalline layer is etched at a faster rate than the epitaxial layer. The method may further include a deposition cycle that includes repeating the exposure of the substrate to the deposition and etchant gases to form a silicon-containing material with a predetermined thickness.

Journal ArticleDOI
TL;DR: In this paper, a uniform cross section along the longitudinal axis can be achieved by optimizing the input V∕III ratio, and small variations in the diameter and length are seen under optimal growth conditions.
Abstract: Vertically-aligned InP nanowires are grown by metalorganic chemical vapor deposition (MOCVD) without the use of a deposited metal catalyst. A surface reconstruction induces indium droplets to form on the surface and thus act as nucleation sites for nanowire growth. Vertical growth from the InP(111)B substrate along with transmission electron microscopy (TEM) analysis indicate epitaxial growth from the substrate in the [111]B direction. A uniform cross section along the longitudinal axis can be achieved by optimizing the input V∕III ratio. Small variations in the diameter and length are seen under optimal growth conditions.

Patent
30 Nov 2005
TL;DR: In this paper, a method of forming an epitaxial film on a substrate is described, which includes providing a substrate, exposing the substrate to a silicon source and a carbon source, and encapsulating the carbon-containing silicon epitaxia with an encapsulating film.
Abstract: In a first aspect, a method of forming an epitaxial film on a substrate is provided. The method includes (a) providing a substrate; (b) exposing the substrate to a silicon source and a carbon source so as to form a carbon-containing silicon epitaxial film; (c) encapsulating the carbon-containing silicon epitaxial film with an encapsulating film; and (d) exposing the substrate to Cl2 so as to etch the encapsulating film. Numerous other aspects are provided.

Journal ArticleDOI
TL;DR: In this article, the metalorganic vapor phase epitaxy (MOVPE) technique was used for the first time on β-Ga2O3 single crystal substrates, which are near-UV transparent and n-type conductive.
Abstract: Epitaxial growth of nitride compounds by the metalorganic vapor phase epitaxy (MOVPE) technique is demonstrated for the first time on β-Ga2O3 single crystal substrates, which are near-UV transparent and n-type conductive. High-quality (0 0 0 1) GaN epi-layer with a narrow bandedge luminescence was obtained using a low temperature conductive buffer layer. InGaN multi-quantum well (MQW) structure was also successfully grown. The first blue light-emitting diode (LED) on β-Ga2O3 with vertical current injection is demonstrated.

Journal ArticleDOI
TL;DR: In this article, a variety of InN thin films grown by molecular-beam epitaxy under both optimized and non-optimized conditions is reported, and optical characterization by absorption and photoluminescence confirms that the bandgap of single-crystalline and poly-crystaline wurtzite InN is 0.70±0.05eV.
Abstract: Detailed transmission electron microscopy, x-ray diffraction (XRD), and optical characterization of a variety of InN thin films grown by molecular-beam epitaxy under both optimized and nonoptimized conditions is reported. Optical characterization by absorption and photoluminescence confirms that the bandgap of single-crystalline and polycrystalline wurtzite InN is 0.70±0.05eV. Films grown under optimized conditions with an AlN nucleation layer and a GaN buffer layer are stoichiometric, single-crystalline wurtzite structure with dislocation densities not exceeding mid-1010cm−2. Nonoptimal films can be polycrystalline and display an XRD diffraction feature at 2θ≈33°; this feature has been attributed by others to the presence of metallic In clusters. Careful indexing of wide-angle XRD scans and selected area diffraction patterns shows that this peak is in fact due to the presence of polycrystalline InN grains; no evidence of metallic In clusters was found in any of the studied samples.

Journal ArticleDOI
TL;DR: In this paper, a planar m-plane GaN film was grown on (100) γ-LiAlO2 and removal of bulk and surface defects was carried out in a horizontal HVPE reactor at 860-890°C.
Abstract: Nonpolar (\(1\bar 100\)) m-plane gallium nitride has been grown heteroepitaxially on (100) γ-LiAlO2 by several groups. Previous attempts to grow m-plane GaN by hydride vapor phase epitaxy (HVPE) yielded films unsuitable for subsequent device regrowth because of the high densities of faceted voids intersecting the films’ free surfaces. We report here on the growth of planar m-plane GaN films on (100) γ-LiAlO2 and elimination of bulk and surface defects. The morphology achieved is smooth enough to allow for fabrication of m-plane GaN templates and free-standing substrates for nonpolar device regrowth. The GaN films were grown in a horizontal HVPE reactor at 860–890°C. Growth rates ranged from 30 µm/h to 240 µm/h, yielding free-standing films up to 250-µm thickness. The m-plane GaN films were optically specular and mirror-like, with undulations having 50–200-nm peak-to-valley heights over millimeter length scales. Atomic force microscopy revealed a striated surface morphology, similar to that observed in m-plane GaN films grown by molecular beam epitaxy (MBE). Root-mean-square (RMS) roughness was 0.636 nm over 25-µm2 areas. Transmission electron microscopy (TEM) was performed on the m-plane GaN films to quantify microstructural defect densities. Basal-plane stacking faults of 1×105 cm−1 were observed, while 4×109 cm−2 threading dislocations were observed in the g=0002 diffraction condition.

Journal ArticleDOI
TL;DR: In this paper, the structure study of MgxZn1−xO films with x = 0.28 and 0.41 MgZnO layers with different crystal structures of cubic and wurtzite was reported.
Abstract: We report on the structure study of MgxZn1−xO films and, in particular, we will focus on MgxZn1−xO layers with x=0.28 and 0.41 MgxZn1−xO layers with different crystal structures of cubic and wurtzite that have been grown by plasma-assisted molecular-beam epitaxy on MgO∕c-sapphire with Mg∕Zn flux ratio control. The MgxZn1−xO films have been characterized by high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction. The dependence of the cation-anion bond length to Mg content has been studied. A virtual crystal model of MgZnO has been applied to interpret the bond-length variation. HRTEM results indicate that the initial stage of the MgZnO growth on a MgO buffer layer starts with a cubic structure even in the case of a wurtzite structure at the end of growth.

Journal ArticleDOI
TL;DR: In this article, a doping approach for p-type ZnO is reported which is reproducible and long-time stable for the zinc oxide layers were doped simultaneously with nitrogen and arsenic in metal organic vapor phase epitaxy.
Abstract: A doping approach for p-type ZnO is reported which is reproducible and long-time stable For p-type doping the zinc oxide layers were doped simultaneously with nitrogen and arsenic in metal organic vapor phase epitaxy The conductivity type of the layers was investigated by scanning capacitance microscopy, a technique based on local capacitance-voltage analysis (C-V) with submicron spatial resolution Depending on the growth parameters, largely extended p-type domains were observed, surrounded by n-type regions The differences in local conductivity type are directly correlated to the topography as measured with atomic force microscopy revealing p-type for smooth, two-dimensional surfaces and n-type signals in the case of three-dimensional island growth or structural defects, ie, microcracks or surface pits

Journal ArticleDOI
TL;DR: In this paper, ZnO nanowires with monodisperse diameters were grown on a - and c-plane sapphire substrates by metalorganic chemical vapor deposition without metal catalysts or templates.