scispace - formally typeset
Search or ask a question

Showing papers on "Epitaxy published in 1990"


Journal ArticleDOI
TL;DR: In this paper, free standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography using electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers.
Abstract: Indirect evidence is presented that free‐standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography. The novel approach uses electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers. Mesoporous Si layers of high porosity exhibit visible (red) photoluminescence at room temperature, observable with the naked eye under <1 mW unfocused (<0.1 W cm−2) green or blue laser line excitation. This is attributed to dramatic two‐dimensional quantum size effects which can produce emission far above the band gap of bulk crystalline Si.

7,393 citations


Journal ArticleDOI
TL;DR: In this article, the physics of the growth mechanisms, characterization of epitaxial structures and device properties of GaAs and other compound semiconductors on Si are reviewed, and the nontrivial problems associated with the heteroepitaxial growth schemes and methods that are generally applied in the growth of lattice mismatched and polar on nonpolar material systems are described in detail.
Abstract: The physics of the growth mechanisms, characterization of epitaxial structures and device properties of GaAs and other compound semiconductors on Si are reviewed in this paper. The nontrivial problems associated with the heteroepitaxial growth schemes and methods that are generally applied in the growth of lattice mismatched and polar on nonpolar material systems are described in detail. The properties of devices fabricated in GaAs and other compound semiconductors grown on Si substrates are discussed in comparison with those grown on GaAs substrates. The advantages of GaAs and other compound semiconductors on Si, namely, the low cost, superior mechanical strength, and thermal conductivity, increased wafer area, and the possibility of monolithic integration of electronic and optical devices are also discussed.

542 citations


Journal ArticleDOI
TL;DR: In this paper, a multilayer AlxGa1−xAs epitaxial films are separated from their growth substrates by undercutting an AlAs release layer in HF acid (selectivity ≳108 for x ≥ 0.4).
Abstract: Epitaxial liftoff is an alternative to lattice‐mismatched heteroepitaxial growth. Multilayer AlxGa1−xAs epitaxial films are separated from their growth substrates by undercutting an AlAs release layer in HF acid (selectivity ≳108 for x≤0.4). The resulting AlxGa1−xAs films tend to bond by natural intermolecular surface forces to any smooth substrate (Van der Waals bonding). We have demonstrated GaAs thin‐film bonding by surface tension forces onto Si, glass, sapphire, LiNbO3, InP, and diamond substrates, as well as self‐bonding onto GaAs substrates. In transmission electron microscopy the substrate and thin‐film atomic lattices can be simultaneously imaged, showing only a thin (20–100 A) amorphous layer in between.

435 citations


Journal ArticleDOI
TL;DR: Arsenic precipitates have been observed in GaAs low-temperature buffer layers (LTBLs) used as "substrates" for normal molecular beam epitaxy growth as mentioned in this paper.
Abstract: Arsenic precipitates have been observed in GaAs low‐temperature buffer layers (LTBLs) used as ‘‘substrates’’ for normal molecular beam epitaxy growth. Transmission electron microscopy has shown the arsenic precipitates to be hexagonal phase single crystals. The precipitates are about 6±4 nm in diameter with a density on the order of 1017 precipitates per cm3. The semi‐insulating properties of the LTBL can be explained in terms of these arsenic precipitates acting as ‘‘buried’’ Schottky barriers with overlapping spherical depletion regions. The implications of these results on LTBL resistivity stability with respect to doping and anneal temperature will be discussed as will the possible role of arsenic precipitates in semi‐insulating liquid‐encapsulated Czochralski‐grown bulk GaAs.

408 citations


Patent
03 Oct 1990
TL;DR: In this article, the authors proposed a method of improving a mechanically prepared surface of alpha silicon carbide for increasing the polytype purity of an epitaxial layer of β-silicon carbide grown thereon.
Abstract: The invention is a method of improving a mechanically prepared surface of alpha silicon carbide for increasing the polytype purity of an epitaxial layer of beta silicon carbide grown thereon. The method comprises decreasing the frequency of exposed higher energy lattice positions along a mechanically prepared {0001} surface of a 6H alpha silicon carbide substrate by adding atoms to vacant lattice positions and by increasing the average height and separation between steps on a mechanically prepared {0001} surface of 6H silicon carbide.

367 citations


Journal ArticleDOI
TL;DR: The discovery of a reentrant layer-by-layer growth during molecular-beam epitaxy of Pt on Pt(111) is reported and explanations of theReentrant behavior based on previous field-ion-microscopy observations are proposed.
Abstract: The discovery of a reentrant layer-by-layer growth during molecular-beam epitaxy of Pt on Pt(111) is reported. Explanations of the reentrant behavior based on previous field-ion-microscopy observations are proposed.

362 citations



Book ChapterDOI
01 Jan 1990
TL;DR: In this paper, NiSi2 films are grown on Si(100) and (111) by ultrahigh-vacuum techniques, and the orientation of the silicide can be controlled by the initial Ni thickness.
Abstract: Continuous and planar single-crystal NiSi2films (<60 A thick) have been grown on Si(100) and (111) by ultrahigh-vacuum techniques. Nickel deposition (<20 A) on atomically clean Si at room temperature, followed by low-temperature heating at ~450°C, results in the growth of epitaxial NiSi2 films whose structure depends critically on the starting Ni thickness. The films are coherent, without misfit dislocations. The orientation of the (111) silicide can be controlled by the initial Ni thickness.

256 citations


Journal ArticleDOI
TL;DR: In this article, the yttria-stabilized zirconia films were grown on Si(100 and Si(111) by pulsed laser deposition and Rutherford backscattering spectroscopy indicates a high degree of crystalline perfection with a channeling minimum yield of 5.3%.
Abstract: Epitaxial yttria‐stabilized zirconia films were grown on Si (100) and Si (111) by pulsed laser deposition. Rutherford backscattering spectroscopy indicates a high degree of crystalline perfection with a channeling minimum yield of 5.3%. A necessary predeposition process is removal of native silicon oxide from the Si prior to film growth. This is done outside the deposition chamber at 23 °C using a wet‐chemical hydrogen‐termination procedure. Epitaxial YBa2Cu3O7−δ films have been grown on these films.

255 citations


Journal ArticleDOI
TL;DR: In this paper, a GaAs buffer layer was grown at low substrate temperatures (250 °C) and the film structures were examined using transmission electron microscopy, showing that the GaAs layer was free of defects or clusters.
Abstract: We have grown film structures by molecular beam epitaxy which include GaAs buffer layers grown at low substrate temperatures (250 °C). The film structures have been examined using transmission electron microscopy. The layers grown at normal temperatures (600 °C) were free of defects or clusters. In contrast, the layer which was grown at low substrate temperatures contained precipitates which have been identified as hexagonal arsenic. The density of the arsenic precipitates is found to be very sensitive to the substrate temperature during growth.

244 citations


Journal ArticleDOI
TL;DR: CeO2 was epitaxially grown for the first time on both (111) and (100) silicon substrates by vacuum evaporation as mentioned in this paper, and the results showed that a CeO2 layer on ( 111) Si has considerably good crystalline quality, whereas that on 100)Si contains a large amount of crystallographic defects, especially in the vicinity of the CeO 2/Si interface.
Abstract: CeO2 layer was epitaxially grown for the first time on both (111) and (100) silicon substrates by vacuum evaporation. Characterization using Rutherford backscattering and reflection high‐energy electron diffraction proved that a CeO2 layer on (111) Si has considerably good crystalline quality, whereas that on (100)Si contains a large amount of crystallographic defects, especially in the vicinity of the CeO2/Si interface. Auger electron spectroscopy analysis showed a uniform concentration distribution of Ce and O throughout the epitaxial layer.

Journal ArticleDOI
TL;DR: In this paper, a tunable doping superlattice laser has been demonstrated, which has a potential tuning range of 220 A and is a candidate for an optical source in future optical communication systems.
Abstract: Delta‐function‐like doping profiles can be obtained in semiconductors by growth‐interrupted impurity deposition during molecular‐beam epitaxy. The spatial localization of dopants is assessed by the capacitance–voltage profiling technique and secondary ion mass spectroscopy which yield profile widths of 20 and 37 A for Be δ‐doped GaAs grown at 500 °C, respectively. The diffusion coefficients of Si, Be, and C in GaAs and of Si in AlxGa1−xAs are determined and diffusion is shown to be negligible at low growth temperatures. At elevated growth temperatures, dopant redistribution occurs during epitaxial growth. The redistribution is shown to be due to (i) diffusion of dopants and (ii) Fermi‐level pinning induced segregation of dopants along the growth axis. Fermi‐level pinning induced segregation of dopants is a novel mechanism which results in a redistribution of dopants predominantly toward the growing surface due to electrostatic attraction of dopants and carriers localized in surface states. This mechamism is shown to be relavant at elevated growth temperatures of ≥600 °C. Electronic devices such as homostructure and heterostructure field‐effect transistors which employ the δ‐doping technique have a number of advantages including (i) high carrier density, (ii) proximity between electron channel and gate electrode, (iii) large breakdown voltage of the gate, and (iv) reduced short‐channel effects. In addition, high transconductances are obtained in such δ‐doped field‐effect transistors. The optical properties of doping superlattices are significantly improved using the δ‐doping technique. Quantum‐confined interband transitions in doping superlattices are observed for the first time in such improved doping superlattices. Furthermore, a tunable doping superlattice laser is demonstrated, which has a tuning range of 35 A. The tunable doping superlattice laser has a potential tuning range of 220 A and is a candidate for a tunable source in future optical communication systems.

Journal ArticleDOI
TL;DR: In this paper, the perovskite axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique has been used to grow YBa2Cu3O7−x−PrBa2cu3O 7−y heterostructures.
Abstract: We have grown YBa2Cu3O7−x‐PrBa2Cu3O7−y heterostructures with the perovskite a axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique. X‐ray diffraction studies indicate little or no formation of the traditional c‐axis normal orientation usually nucleated on these substrates, while ion channeling, transmission electron microscopy (TEM), and Raman scattering studies reveal a highly ordered crystalline structure similar in quality to that obtained in the best c‐axis oriented films. Superconducting transition temperatures, for current transport in the plane of the films, consistently exceed 80 K, but are probably lower than the optimum 92 K transition expected for YBa2Cu3O7−x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions.

Journal ArticleDOI
TL;DR: In this paper, a diamond thin film was grown epitaxially on high pressure synthesized cubic boron nitride (c•BN) particles by using dc plasma chemical vapor deposition.
Abstract: Diamond thin films have been grown epitaxially on high‐pressure synthesized cubic boron nitride (c‐BN) particles by using dc plasma chemical vapor deposition. At the early growth stage of the film on c‐BN{111} surfaces, the island structure is observed and the number density of islands is about 1011 cm−2. The growth and the coalescence of islands are also found by scanning electron microscopy observation. The continuous film is obtained at the thickness of about 2000 A and the surface of the film is rather smooth. The Raman peak of the epitaxial diamond film shows the shift toward the lower wave number due to the tensile stress involved in the film.

Journal ArticleDOI
TL;DR: In this article, the role of hydrogen surface passivation in achieving low-temperature silicon epitaxy by chemical vapor deposition processes was investigated and it was shown that hydrogen passivation by HF pretreatment leads to two divergent temperature ranges where epitaxy is successful, those being a low temperature range, 425≲T≲650°C, and a high temperature regime, T≳750°C.
Abstract: We report on the role of hydrogen surface passivation in achieving low‐temperature silicon epitaxy by chemical vapor deposition processes. Upon insertion of an HF‐etched silicon wafer into an epitaxial silicon deposition apparatus, residual contamination of the Si surface is negligible. Si 2p core level photoemission spectra demonstrate that the silicon surface is stable in air and free of SiO2 for a time period of minutes. The predominant passivating species is found to be silicon hydride. We demonstrate that hydrogen passivation by HF pretreatment leads to two divergent temperature ranges where epitaxy is successful, those being a low‐temperature range, 425≲T≲650 °C, and a high‐temperature regime, T≳750 °C. Additionally, we employ temperature‐programmed desorption techniques to elucidate the role of hydrogen in the transition to a steady‐state growth process, employing ultrahigh vacuum/chemical vapor deposition as the model system.

Journal ArticleDOI
TL;DR: In this paper, both doped and undoped homoepitaxial diamond films were fabricated using microwave plasma-enhanced chemical vapor deposition (CVD), and the conductivity of the diamond film is strongly affected by the surface treatment.
Abstract: Both doped and undoped homoepitaxial diamond films were fabricated using microwave plasma-enhanced chemical vapor deposition (CVD). The conductivity of the diamond film is strongly affected by the surface treatment. In particular, exposure of film surface to a hydrogen plasma results in the formation of a conductive layer which can be used to obtain linear (ohmic) I-V characteristics of the Au/diamond contacts, regardless of the doping level. It is shown how the proper chemical cleaning of the boron-doped homoepitaxial diamond surface allows the fabrication of Au-gate Schottky diodes with excellent rectifying characteristics at temperatures of at least 400 degrees C. >

Journal ArticleDOI
TL;DR: In this paper, the first observation of the room temperature stimulated emission near UV from a GaN film which was grown by metalorganic vapor phase epitaxy on a (0001) sapphire substrate using an AlN buffer layer was reported.
Abstract: We report the first observation of the room temperature stimulated emission near UV from a GaN film which was grown by metalorganic vapor phase epitaxy on a (0001) sapphire substrate using an AlN buffer layer This indicates that the GaN film is promising for the realization of an UV laser diode

Journal ArticleDOI
TL;DR: In this article, the authors observed matching face relationship is FeSiSi2(100)/Si(001), with the azimuthal orientation being FeSi2[010]‖‖Si〈110〉.
Abstract: Epitaxial thin films of the semiconducting transition metal silicide, beta‐FeSi2, were grown on (001) silicon wafers. The observed matching face relationship is FeSi2(100)/Si(001), with the azimuthal orientation being FeSi2[010]‖‖Si〈110〉. This heteroepitaxial relationship has a common unit mesh of 59 A2 area, with a mismatch of 2.1%. There is a strong tendency toward island formation within this heteroepitaxial system.

Journal ArticleDOI
TL;DR: In this article, a homo-epitaxially grown GaN on a thin GaN buffer layer was shown to have high purity and high crystalline quality, and the magnitude of the strain of the homogeneous GaN was less than half that of a hetero-EPITaxially generated GaN.

Journal ArticleDOI
TL;DR: Porous silicon is a morphological form of single-crystal silicon obtained by anodic attack in concentrated hydrofluoric acid solutions as mentioned in this paper, and the formation mechanism of the pore network is still not well understood.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated reaction-forming of silicon carbide by the infiltration of carbonaceous preforms using alloyed silicon melts, in order to synthesize composite materials free of the residual silicon phase that has previously limited mechanical properties and upper use temperatures.
Abstract: The authors have investigated reaction-forming of silicon carbide by the infiltration of carbonaceous preforms using alloyed silicon melts, in order to synthesize composite materials free of the residual silicon phase that has previously limited mechanical properties and upper use temperatures. In this approach, rejection of the alloying component(s) from the primary silicon carbide phase into the remaining melt results in the formation of a secondary refractory phase, such as a silicide, in place of residual free silicon. Experiments conducted in the Si-Mo melt system show that relatively dense ({gt}90%) silicon carbide-molybdenum silicide materials free of residual silicon and residual carbon can be obtained. A model for reactive infiltration based on time-dependent permeabilities is proposed. Processing variables important for control of the reaction rate relative to the infiltration rate, and associated processing flaws, are discussed.

Journal ArticleDOI
TL;DR: In this article, the growth mechanism of GaAs and AlGaAs in migration-enhanced epitaxy was investigated by RHEED observation and optical scattering measurements, and the observed step-flow growth was explained by considering the different chemical characteristics of the steps along the [110] and [ 1 10] directions.

Journal ArticleDOI
15 Mar 1990-Nature
TL;DR: In this paper, the authors reported STM imaging of smectic liquid crystals (4'-n-n-octyl-4-cyanobiphenyl (8CB)) condensed on a molybdenum disulphide single crystal.
Abstract: THE molecular alignment of liquid crystals on solid substrates is important both to fundamental issues in physics and biology and in practical applications such as optoelectronic devices. The structure of adsorbed phases is determined to a large extent by the balance of molecule–molecule and substrate–molecule forces at the solid-adsorbate interface. Scanning tunnelling microscopy (STM) now allows the possibility of direct observation of the interfacial structure with molecular resolution, and has been used to study positional and orientational order in monolayers of organic molecules on graphite1–4. Here we report STM imaging of smectic liquid crystals (4'-n-octyl-4-cyanobiphenyl (8CB)) condensed on a molybdenum disulphide single crystal. The anchoring structure is different from that on graphite4, and is unusual in that the molecules are aligned so that intermolecular interactions are energetically unfavourable. The influence of interactions with the substrate is clearly important in this case, and this is further supported by an apparent degree of epitaxy in the adsorbed layer.

Journal ArticleDOI
A. Sherman1
TL;DR: In this paper, chemical vapor deposition has been used to deposit titanium nitride (TiN) on silicon wafers at low pressures in a cold-wall single-wafer reactor.
Abstract: Chemical vapor deposition has been used to deposit titanium nitride (TiN) on silicon wafers at low pressures in a cold-wall single-wafer reactor. Experiments are reported for pressures in the range of 100-300 mtorr and temperatures between 450{degrees}-700{degrees}C, with titanium tetrachloride and ammonia as reactants. Both hydrogen and nitrogen are evaluated as diluents. Deposition rates as high as 1000 {angstrom}/min have been achieved. The chemical nature of the films are evaluated by Auger and RBS techniques, while the morphology is depicted by SEM. For the most part, the films are stoichiometric and contain small quantities of oxygen, chlorine, and hydrogen.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the equilibrium hydrogen surface coverage on Si(100) during silicon epitaxy using SiH4 in a rapid thermal chemical vapor deposition (CVD) reactor.
Abstract: The equilibrium hydrogen surface coverage on Si(100) during silicon epitaxy using SiH4 has been measured in a rapid thermal chemical vapor deposition reactor. The hydrogen coverage could be ‘‘frozen out’’ completely on the surface by a rapid cool‐down and pump‐down of the reactor up to temperatures of ≂575 °C; at temperatures above 575 °C only partial ‘‘freeze‐out’’ is achieved. Surface hydrogen was titrated in situ using the reactor as a thermal desorption spectrometer. Epitaxial silicon films were grown in the temperature range 450–700 °C and the film growth kinetics was correlated with the equilibrium hydrogen coverage. The growth mechanism changes from the low‐temperature regime, where the surface is hydrogen covered, to the high‐temperature regime, where the surface is essentially clean.

Journal ArticleDOI
TL;DR: In this article, a planar doping of InGaAs has been shown to achieve C diffusion coefficient of <10-16 cm2 s-1 at 950°C, in agreement with other reports.

Journal ArticleDOI
TL;DR: In this article, the first use of ellipsometry as a real-time monitor of III-V semiconductor crystal growth by molecular beam epitaxy was reported, specifically growth of GaAs and AlGaAs from arsine, triethylgallium, and triethylaluminum sources.
Abstract: We report the first use of ellipsometry as a real‐time monitor of III‐V semiconductor crystal growth by molecular beam epitaxy, specifically growth of GaAs and AlGaAs from arsine, triethylgallium, and triethylaluminum sources. Our results provide new insight into the oxide desorption process and show a sensitivity of ±0.03 in compositions x>0.2 for 10 A thickness increments of AlxGa1−xAs during initial deposition on GaAs.

Journal ArticleDOI
TL;DR: In this article, the epitaxial growth of silicon on Si(001)•(2×1) substrates at temperatures between 580 and 850 K was studied using scanning tunneling microscopy (STM).
Abstract: The epitaxial growth of silicon on Si(001)‐(2×1) substrates at temperatures between 580 and 850 K is studied using scanning tunneling microscopy (STM). The growth is strongly anisotropic, forming long narrow structures only a few dimers wide but more than 100 A long. Models are proposed for the two types of antiphase boundaries that are observed on the epitaxially grown surfaces.

Journal ArticleDOI
TL;DR: In this article, a thin film of ferroelectric bismuth titanate Bi4Ti3O12 has been grown by pulsed laser deposition on single-crystal substrates.
Abstract: Epitaxial thin films of ferroelectric bismuth titanate Bi4Ti3O12 have been grown by pulsed laser deposition on single‐crystal [100] SrTiO3 substrates. Bismuth titanate has a high Curie temperature (675 °C) and saturation polarization values of 4 and 50 μC/cm2 along the c and b axis, respectively. Its a,b lattice parameters allow thin‐film growth on substrates such as SrTiO3, LaAlO3, MgO, etc. These single crystalline films exhibit good quality as evidenced by x‐ray diffraction, Rutherford backscattering, and transmission electron microscopy. Applications for these films include memory devices and optical displays.

Journal ArticleDOI
TL;DR: In this paper, the dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x-ray diffraction, Hall effect, and secondary ion mass spectrometry measurements.
Abstract: Epitaxial layers of GaAs have been grown by metalorganic molecular beam epitaxy (MOMBE) with atomic carbon concentrations ranging from 4×1017 to 3.5×1020 cm−3. The dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x‐ray diffraction, Hall effect, and secondary‐ion mass spectrometry measurements. For atomic carbon concentrations in excess of 1×1019 cm−3, the hole concentrations are less than the corresponding atomic carbon concentrations. Lattice parameter shifts as large as 0.2% are observed for carbon concentrations in excess of 1×1020 cm−3, which results in misfit dislocation generation in some cases due to the lattice mismatch between the C‐doped epilayer and undoped substrate. Over the entire range of carbon concentrations investigated, Vegard’s law accurately predicts the observed lattice contraction.