Showing papers on "Epitaxy published in 1988"

Cooperative growth phenomena in silicon/germanium low-temperature epitaxy

Abstract: A series of Si:Ge alloys and structures has been prepared by ultrahigh‐vacuum chemical vapor deposition. Alloys of composition 0≤Ge/Si≤0.20 are readily deposited at T=550 °C. Commensurate, defect‐free strained layers are deposited up to a critical thickness, whereupon the accumulated stress in the films is accommodated by the formation of dislocation networks in the substrate wafers. A cooperative growth phenomenon is observed where the addition of 10% germane to the gaseous deposition source accelerates silane’s heterogeneous reaction rate by a factor of 25. A model is proposed where Ge acts as a desorption center for mobile hydrogen adatoms on the Si[100] surface, accelerating heterogeneous silane pyrolysis by the enhanced availability of chemisorption sites.

Single-Crystal YBa2Cu3O7-x Thin Films by Activated Reactive Evaporation

Abstract: By means of the activated reactive evaporation, YBa2Cu3O7-x single-crystal thin films with the c axis perpendicular to the substrate plane have been directly and epitaxially grown on the (100) surface of SrTiO3. The substrate temperature was kept below 600°C and the oxidation treatment was performed at below 500°C. The ac-resistive measurement for a film with 2000 A thickness gave a sharp superconducting transition, where the endpoint was 90.2 K and ΔTc(10–90%)=1.7 K. From the complex susceptibility measurement we confirmed the Meissner effect as well as the structural uniformity of the specimen.

Migration-Enhanced Epitaxy of GaAs and AlGaAs

Abstract: Surface migration is effectively enhanced by evaporating Ga or Al atoms onto a clean GaAs surface under an As-free or low As pressure atmosphere. This characteristic was utilized by alternately supplying Ga and/or Al and AS4 to the substrate surface for growing atomically-flat GaAs-AlGaAs heterointerfaces, and also for growing high-quality GaAs and AlGaAs layers at very low substrate temperatures. The migration characteristics of surface adatoms have been investigated through reflection high-energy electron diffraction measurements. It was found that different growth mechanisms are operative in this method at both high and low temperatures. Both these mechanisms are expected to yield flat heterojunction interfaces. By applying this method, GaAs layers and GaAs-AlGaAs single quantum-well structures with excellent photoluminescence were grown at substrate temperatures of 200 and 300degC, respectively.

Luminescence of heteroepitaxial zinc oxide

Abstract: Thin layers of ZnO were grown on (0001) oriented sapphire by organometallic chemical vapor deposition. Low‐temperature photoluminescence indicates that near‐band‐edge luminescence dominates the spectrum. In contrast to bulk grown material deep level luminescence for the layers is relatively weak.

Molecular‐beam epitaxy growth of tilted GaAs/AlAs superlattices by deposition of fractional monolayers on vicinal (001) substrates

Abstract: We report the successful growth of GaAs/AlAs superlattices having interface planes tilted with respect to the substrate surface plane. The amount of tilt and the superlattice period may be controlled by adjusting the growth parameters. The tilted superlattices (TSL’s) were produced by depositing fractional monolayer superlattices (GaAs)m(AlAs)n, with p=m+n≂1, on vicinal (001) substrates. We demonstrate the growth of quantum wirelike structures produced by placing short sections of TSL between horizontal layers of AlAs. Variations of the TSL period and tilt, both on uniform surfaces and on surfaces containing defects, yield insight to the growth kinetics and to the influence of variations in the growth parameters during molecular‐beam epitaxy growth.

Chemical vapor deposition and characterization of 6H‐SiC thin films on off‐axis 6H‐SiC substrates

Abstract: High‐quality, monocrystalline 6H‐SiC thin films have been epitaxially grown on 6H‐SiC {0001} substrates which were prepared 3° off‐axis from 〈0001〉 towards 〈1120〉 at 1773 K via chemical vapor deposition (CVD). Essentially, no defects were generated from the epilayer/substrate interface as determined by cross‐sectional transmission electron microscopy (XTEM). Double positioning boundaries which were observed in β‐SiC grown on 6H‐SiC substrates were eliminated as confirmed by plan‐view TEM. A strong dependence of the surface morphology of the as‐grown thin films on the tilting orientation of the substrates was observed and reasons for this phenomenon are discussed. The unintentionally doped 6H‐SiC thin films always exhibit n‐type conduction with a carrier concentration on the order of 1016 cm−3. Au‐6H‐SiC Schottky barrier diodes were fabricated on the CVD 6H‐SiC thin films and it was found that the leakage current at a reverse bias of 55 V was only 3.2×10−5 A/cm2. This is compared to SiC films grown on oth...

Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

Abstract: We demonstrate that lanthanum gallate (LaGaO3) has considerable potential as an electronic substrate material for high‐temperature superconducting films. It provides a good lattice and thermal expansion match to YBa2Cu3O7−x, can be grown in large crystal sizes, is compatible with high‐temperature film processing, and has a reasonably low dielectric constant (e≂25) and low dielectric losses. Epitaxial YBa2Cu3O7−x films grown on LaGaO3 single‐crystal substrates by three techniques have zero resistance between 87 and 91 K.

Metalorganic vapor phase epitaxy of low-resistivity p-type ZnSe

Abstract: Low‐resistivity p‐type ZnSe layers have been successfully grown on GaAs substrates by metalorganic vapor phase epitaxy with the use of dimethylzinc and diethylselenide as source materials and lithium nitride as the dopant. The lowest resistivity achieved is 0.2 Ω cm, and the highest carrier concentration is 9×1017 cm−3. ZnSe p‐n diodes fabricated by this technique have shown blue emission; the spectral peak is located at 467 nm.

Controlled carbon doping of GaAs by metalorganic vapor phase epitaxy

Abstract: The controlled incorporation of carbon has been demonstrated for the metalorganic vapor phase epitaxy of GaAs. Carbon levels between 1016 and 1019 cm−3 can be achieved under typical growth conditions by using Ga(CH3)3 and either As(CH3)3 or mixtures of As(CH3)3 and AsH3. The carbon incorporation into GaAs goes through a minimum with growth temperature at ∼650 °C when using Ga(CH3)3 and As(CH3)3. The controlled addition of AsH3 monotonically decreases the carbon incorporation. The high carbon levels (≳1–2×1019 cm−3), greater than the reported solid solubility, are thermally stable with a low diffusion coefficient. The GaAs:C layers exhibit a low deep level concentration, ∼1013 cm−3, with only a single midgap trap present.

Substrate-polarity dependence of metal-organic vapor-phase epitaxy-grown GaN on SiC

Abstract: Single‐crystal gallium nitride was grown on each of the two polar {0001} planes of 6H‐silicon carbide substrates utilizing metal‐organic vapor‐phase epitaxy. The substrate polarity is clearly shown to strongly influence the surface morphology and the photoluminescence property of the layer. The examination of the layer surfaces using x‐ray photoelectron spectroscopy revealed that {0001} GaN grown on the basal planes of SiC changes its polarity in accordance with the substrate polarity.

Coaxial impact-collision ion scattering spectroscopy (CAICISS): A novel method for surface structure analysis

Abstract: A novel low-energy ion scattering spectrometer, in which an ion source and an energy analyzer are arranged coaxially so that the experimental scattering angle is just 180°, has been constructed. This mode of low-energy ion scattering spectroscopy, which we call coaxial impact-collision ion scattering spectroscopy (CAICISS), has several advantages. For example, CAICISS is suitable for in situ observation of various surface processes (e.g., epitaxial film growth at semiconductor surfaces) because of its geometrical simplicity. Preliminary experiments using the CAICISS apparatus have been made for a Au/Si(111) surface.

Handbook of thin-film deposition processes and techniques : principles, methods, equipment, and applications

Abstract: Recent Changes in the Semiconductor Industry Deposition Technologies and Applications: Introduction and Overview Silicon Epitaxy by Chemical Vapor Deposition Chemical Vapor Deposition of Silicon Dioxide Films Metal Organic Chemical Vapor Deposition: Technology and Equipment Feature Scale Modeling The Role of Metrology and Inspection in Semiconductor Processing Contamination Control, Defect Detection, and Yield Enhancement in Gigabit Manufacturing Sputtering and Sputter Deposition Laser and Electron Beam Assisted Processing Molecular Beam Epitaxy: Equipment and Practice Ion Beam Deposition Chemical Mechanical Polishing Organic Dielectrics in Multilevel Metalization of Integrated Circuits Performance, Processing, and Lithography Trends Index

Band-Gap Energy Anomaly and Sublattice Ordering in GaInP and AlGaInP Grown by Metalorganic Vapor Phase Epitaxy

Abstract: The previously reported photoluminescence(PL)-peak-energy anomaly problem for Ga0.5In0.5P grown on GaAs by metalorganic vapor phase epitaxy (MOVPE) was studied in detail. X-ray microprobe analysis, and optical transmission spectra measurements were carried out to examine alloy compositions and band-gap energies (Egs), respectively. The MOVPE growth condition dependence of {1/2, 1/2, 1/2} superlattices (SLs) on the cation sublattice in Ga0.5In0.5P was studied in detail, using transmission electron microscopy. The correlation between the Eg anomaly and the SLs was examined in detail and established. Raman spectra seemed to show zone-folding effects due to the monolayer SL. A similar Eg anomaly was reported for AlGaInP. AlGaInP and AlInP were also found to show the same SLs.

A model for the surface chemical kinetics of GaAs deposition by chemical‐beam epitaxy

Abstract: Recently we have reported the measurement of reflection high‐energy electron diffraction intensity oscillations during chemical‐beam epitaxy of GaAs using triethylgallium (TEG) and As2 derived from an arsine cracker [Appl. Phys. Lett. 50, 19 (1987)]. In this study we observed a significant variation of the GaAs growth rate with substrate temperature at constant TEG flux. In addition, the variation of growth rate with incident flux at constant temperature was found to be nonlinear below approximately 500 °C and linear above 500 °C for incident fluxes yielding maximum growth rates between 0.2 and 1.8 monolayers/s. We have developed a model of the surface pyrolysis of triethylgallium which explains the qualitative behavior of the above data. The model assumes the existence of adsorbed triethyl, diethyl, and monoethyl gallium species as well as adsorbed ethyl radicals. As a starting point, the rate limiting step to epitaxial incorporation of atomic gallium is assumed to be cleavage of the second ethyl–gallium...

Characterization of p‐type GaAs heavily doped with carbon grown by metalorganic molecular‐beam epitaxy

Abstract: p‐type GaAs with doping levels of up to 5.8×1020 cm−3 has been grown by metalorganic molecular‐beam epitaxy (MOMBE) using carbon (C) as a dopant. The mobility and minority‐carrier diffusion length of the C‐doped MOMBE layers were comparable to those of Be‐doped MBE layers. The diffusion coefficient of C at 900 °C was estimated to be 6×10−15 cm2 /s which is about two orders of magnitude less than that of Be (1×10−12 cm2 /s). In addition, the lattice constant of C‐doped GaAs was found to be 5.6533 A which completely matches that of the substrate, while the lattice constant of Be‐doped GaAs decreases to 5.6467 A at a doping level of 2×1020 cm−3 as reported by Lievin et al. [Inst. Phys. Conf. Ser. No. 79, 595 (1985)].

Defects in electronic materials

Abstract: This book collects papers on semiconductor materials. Topics include: oxygen precipitation formation, silicon, boron complexes in silicon, radiation-induced defects in indium antinomide, gallium arsenides, vapor phase epitaxy, gallium and indium phosphides, crystal doping, and deep level transient spectroscopies.

Si/Ge0.3Si0.7/Si heterojunction bipolar transistor made with Si molecular beam epitaxy

Abstract: GexSi1−x heterobase n‐p‐n heterojunction bipolar transistor structure has been grown completely by Si molecular beam epitaxy for the first time. A collector‐top type design was adopted. The 3000 A p‐type Ge0.3Si0.7 heterobase layer with 5×1019 cm−3 doping level was grown on an emitter layer which was an arsenic highly doped substrate (7×1019 cm−3), followed by a 5000 A n‐type Si collector layer with 7×1017 cm−3 doping level. Low‐temperature device processes under 650 °C were used to avoid thermal diffusion of impurities. Common‐emitter current gain hFE with a 100‐μm‐diam emitter was 15 at 2×104 A/cm2 collector current density. Compared with a usual Si‐base bipolar transistor of the same size and doping level, an improvement in current gain was observed. Furthermore, GexSi1−x/Si (x=0.1–0.4) p‐n junction interfaces were investigated by current‐voltage and capacitance‐voltage measurements and transmission electron microscopy observation.

Grazing incidence X-ray diffraction of lead monolayers at a silver (111) and gold (111) electrode/electrolyte interface

Abstract: : Using grazing incidence geometry and a thin layer cell, x-ray scattering has been used to study the structure of electrochemically deposited monolayers of lead on silver (111) and gold (111) electrodes in-situ. For the lead monolayer deposited on sliver, the lead was found to order in a hexagonoal closed packed (hcp) geometry with the lead lattice compresssed 1.2% relative to bulk lead. A rotational epitaxy angle of 4.4 deg was observed. From the width of the first order diffraction peak, the domain size of the lead was determined to be 300 A indicating that even when deposited from a solution, the lead forms a well ordered two-dimensional solid. On a gold (111) substrate, the lead monolayer was again found to order into a hcp layer, incommensurate with the gold. The lead was compressed 0.7% relative to bulk lead, with a domain size 200 A. Keywords: X-ray electrode; Lead(Metal); Gold electrode; Interface structure; Electrodeposition.

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

Abstract: Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

In situ epitaxial growth of Y1Ba2Cu3O7−x films by molecular beam epitaxy with an activated oxygen source

Abstract: Highly oriented, epitaxial Y1Ba2Cu3O7−x thin films were prepared on MgO(100) by molecular beam epitaxy at a substrate temperature of 550–600 °C. The in situ growth was achieved by incorporating reactive oxygen species produced by a remote microwave plasma in a flow‐tube reactor. The epitaxial (001) orientation is demonstrated by x‐ray diffraction and ion channeling. In situ reflection high‐energy electron diffraction showed that a layer‐by‐layer growth has produced a well‐ordered, atomically smooth surface in the as‐grown tetragonal phase of an oxygen stoichiometry of 6.2–6.3. A 500 °C anneal in 1 atm of O2 converted the oxygen content to 6.7 to 6.8. Typical superconducting transport properties of an Y1Ba2Cu3O7−x film 1000 A thick are ρ(300 K)=325 μΩ cm, ρ(300 K)/ρ(100 K)=2.4, Tc(onset)=92 K, and Tc(R=0)=82 K. The transport Jc at 75 K is 1×105 A/cm2, and increases to 1×106 A/cm2 at 70 K.

Epitaxial Al2O3 films on Si by low‐pressure chemical vapor deposition

Abstract: Heteroepitaxial Al2O3 films were grown successfully on (100)Si substrates at substrate temperatures above 1000 °C by low‐pressure chemical vapor deposition with the use of N2 bubbled Al(CH3)3 and N2O. From reflection high‐energy electron diffraction analysis, the epitaxial films were found to be γ‐Al2O3 with an orientation relation of (100)Al2O3//(100)Si. Capacitors with 700‐A‐thick Al2O3 films as gate insulators were fabricated and showed high‐frequency capacitance‐voltage characteristics without hysteresis. An interface state density of 1.7×1011 cm−2 eV−1 was observed by using quasistatic capacitance‐voltage measurements. The leakage current was 9.7×10−11 A/cm2 at a gate voltage of 3.0 V.

Heteroepitaxial Growth and the Effect of Strain on the Luminescent Properties of GaN Films on (11\bar{2}0) and (0001) Sapphire Substrates

Abstract: GaN films grown on (11 0) and (0001) sapphire substrates are characterized by X-ray Bond's method and the low temperature photoluminescence measurement. The GaN films are found to be strained by the biaxial compressive stress. From the measured strain and the shift of PL peak energy, the deformation potential of GaN (the relation between the strain parallel to the c-axis and the band gap energy) is found to be 12 eV. The origin of this compressive stress is discussed.

The nature of molecular beam epitaxial growth examined via computer simulations

Abstract: Man-made synthetic structures involving epitaxially grown thin films of one or more compound semiconductors have been finding an increasingly important role in semiconductor device technology.1 Remarkable advances have been made over the past decade in the realization of a variety of such structures involving III-V, II-VI. and IV-VI compound semiconductors, as well as combinations of semiconductors with dielectrics and metals.' The major part of this progress has come about primarily due to the advent of, and refinements in, two vapor phase growth techniques — molecular beam epitaxy (MBE)' and metal-organic chemical vapor deposition (MO-CVD).3 The underlying motivation has been the remarkably altered and potentially useful electronic and optical properties of electrons, holes, and light arising from their confinement in a quasi-two-dimensional environment in the ultrathin films (thickness less than the particle deBroglie wavelength).4 However, confinement of the par- ticles in such ultrathin laye...

New approach to the atomic layer epitaxy of GaAs using a fast gas stream

Abstract: A new growth method has been developed for the atomic layer epitaxy of GaAs. The gas system was based on a conventional metalorganic vapor phase epitaxial system but the decomposition of methylgallium was suppressed in the stagnant layer by using a fast pulsed gas stream from a jet nozzle. The method enabled us to grow high purity epitaxial layers with a clear self‐limiting mechanism even at 560 °C. The variations in the growth rate with respect to various growth parameters were explained by the rate equations based on the selective adsorption of methylgallium on surface As atoms. The decomposition rate of methylgallium on the surface had an activation energy of 42 kcal/mole from 440 to 560 °C.

Ion implantation and annealing of crystalline oxides and ceramic materials

Abstract: The response of several crystalline oxides or ceramic materials to ion implantation and subsequent thermal annealing is described. For both SrTiO 3 and CaTiO 3 single crystals, the near-surface region can be turned amorphous by relatively low doses of heavy ions (Pb, 10 15 /cm 2 , 540 keV). During annealing, the amorphous region recrystallizes epitaxially with the underlying substrate by simple solid-phase epitaxy, and the crystallization kinetics have been determined for both of these materials. In Al 2 O 3 , the amorphous phase of the pure material is produced by a stoichiometric implant at liquid nitrogen temperature. During annealing, the amorphous film crystallizes in the (crystalline) γ phase, followed by the transformation of the γ to the α phase at a well-defined interface. The kinetics characterizing the growth of α-Al 2 O 3 have been determined. Preliminary results are presented on the effect of impurities (Fe) on the nature and kinetics of the crystallization of amorphous Al 2 O 3 .