bluuebunny/crossref_metadata_2025 huggingface dataset:
Amorphous SiN films grown by hot-filament chemical vapor deposition using monomethylamine
Authors: Yasui Kanji , Katoh Hirohisa , Komaki Kazuki , Kaneda Shigeo
Published: July 2002

Hot-filament chemical vapor deposition (hot-filament CVD) of silicon nitride films has been studied using silane and monomethylamine as source gases for the deposition temperature 600–800 °C. The deposition rate was about one order larger than that of thermochemical vapor deposition (thermo-CVD) using the same gases. The activation energy of the growth rate was 0.2 eV smaller than that of thermo-CVD. The hydrogen content was below the detection limit of infrared absorption measurements even in the film deposited at 600 °C. The film surface deposited at 700 °C had a smooth specular surface and the flatness of the hot-filament CVD films was the same as that of thermo-CVD films deposited at 100–200 °C higher temperatures.
Observation of room-temperature blue shift and bistability in a strained InGaAs-GaAs 〈111〉 self-electro-optic effect device
Authors: Goossen K. W. , Caridi E. A. , Chang T. Y. , Stark J. B. , Miller D. A. B. , Morgan R. A.
Published: July 2002

We have observed room-temperature exciton blue shift with applied voltage in a 〈111〉 In0.1Ga0.9As-GaAs p-i-n multiple quantum well modulator. We have also observed optically induced bistability in a symmetric self-electro-optic effect device circuit composed of these modulators. Very large (2.5:1) ratios of photocurrent were obtained with only 0–3 V applied bias.
Quarter-wave Bragg reflector stack of InP-In0.53Ga0.47As for 1.65 μm wavelength
Authors: Deppe D. G. , Gerrard N. D. , Pinzone C. J. , Dupuis R. D. , Schubert E. F.
Published: July 2002

Quarter-wave semiconductor mirrors of InP-In0.53Ga0.47As for high reflectivity at 1.65 μm wavelength are epitaxially grown using metalorganic chemical vapor deposition. Doping of the In0.53Ga0.47As layers is found to be critical for high reflectivity at wavelengths corresponding to the In0.53Ga0.47As band gap. n-type doping reduces the band-to-band absorption resulting in high reflectivity while p-type doped mirrors show reduced reflectivity.
Current-controlled negative differential conductivity in semi-insulating GaAs
Authors: Li Z.-M. , McAlister S. P. , McMullan W. G. , Hurd C. M. , Day D. J.
Published: July 2002

The leakage current in the semi-insulating substrate of a GaAs device measured in a conventional voltage-controlled experiment shows hysteresis. Experiments in constant-current conditions show that this arises from an S-type negative differential conductivity. These features are incompatible with the conventional trap-fill-limited model, and we outline an alternative explanation based on the impact ionization of multiple deep level traps.
Nucleation of amorphous germanium from supercooled melts
Authors: Stiffler S. R. , Thompson Michael O. , Peercy P. S.
Published: July 2002

Thin germanium films on SiO2 completely melted by pulsed laser irradiation cool rapidly by thermal conduction to the substrate until they solidify. In situ measurements indicate that the liquid is supercooled by 420–530 K with respect to the crystalline phase prior to solidification. Cross-sectional transmission electron microscopy reveals nucleation events at the Ge/SiO2 interface. The microstructure of these events is comprised of a very fine grained (5–15 nm) polycrystalline core with much larger grains extending laterally and toward the free surface. It is believed that nucleation of the amorphous phase, which was subsequently converted to the fine-grained material, initiated solidification.
Solid phase reaction and electrical properties in Zr/Si system
Authors: Yamauchi T. , Zaima S. , Mizuno K. , Kitamura H. , Koide Y. , Yasuda Y.
Published: July 2002

The specific contact resistivity and the Schottky barrier height in the Zr/Si system have been measured as a function of annealing temperature. The specific contact resistivity decreases with increasing annealing temperature and a minimum value of 4×10−8 Ω cm2 is obtained after annealing at 420 °C in a vacuum, which is about two orders of magnitude lower than that of the Al (1.5% Si)/n+-Si system. The formation of ZrSi2 is observed at annealing temperatures above 350 °C, which can be considered to be related to the lowering of contact resistance. The Schottky barrier heights of as-grown Zr films are 0.61 eV for p-type Si and 0.52 eV for n-type Si.
Intense photoluminescence between 1.3 and 1.8 μm from strained Si1−xGex alloys
Authors: Noël J.-P. , Rowell N. L. , Houghton D. C. , Perovic D. D.
Published: July 2002

Intense photoluminescence (PL) from strained, epitaxial Si1−xGex alloys grown by molecular beam epitaxy is reported with measured internal quantum efficiencies up to 31% from random alloy layers, single buried strained layers, and multiple quantum wells. Samples deposited at ∼400 °C exhibited low PL intensity, whereas annealing at ∼600 °C enhanced the intensity by as much as two orders of magnitude. This anneal treatment was found to be optimal for removal of grown-in defect complexes without creating a significant density of misfit dislocations. PL peak energies at 4.2 K varied from 620 to 990 meV for Ge fractions from 0.53 to 0.06, respectively. Efficient PL was due to exciton accumulation in the strained Si1−xGex layers of single and multiple quantum wells, where the band gap was locally reduced. Optical transitions associated with the PL occurred without phonon assistance.
Graphitic clusters in hydrogenated amorphous carbon induced by keV-ion irradiation
Authors: Compagnini G. , Foti G. , Reitano R. , Mondio G.
Published: July 2002

Energy gap and hydrogen concentration have been measured in hydrogenated amorphous carbon (a-C:H) after bombardment with 100 keV He+ and 300 keV Ar+ ion beams, up to ion fluences 3×1016 ions/cm2. a-C:H films have been obtained by ion irradiation at low ion fluences of polystyrene layers and with a subsequent low-temperature annealing (400 °C, 10 min). Experimental values for the energy gap (2.5–0.5 eV) and hydrogen concentration (7.4×1022–1.8×1022 H atoms/cm3) have been interpreted in terms of a graphitic cluster structure with a different size (3–20 Å). We were able to determine experimentally the value of the bond integral ‖β‖ and we found it in good agreement with the calculated one for graphite.
Boron delta doping in Si and Si0.8Ge0.2 layers
Authors: Jorke H. , Kibbel H.
Published: July 2002

By using an elemental boron effusion cell, B delta doping structures (5×1013 B atoms/cm2) were grown on Si (100) by molecular beam epitaxy at different substrate temperatures and cap layer compositions (Si and Si0.8Ge0.2). Close to the delta interface the B profiles are characterized by an exponential decay in growth direction. For the Si cap the results suggest the existence of a transition from equilibrium segregation (exponential decay length ≂20 nm) to kinetically limited segregation (transition temperature ≂600 °C at 0.1 nm/s). The doping profiles also give evidence of a temporal change of the segregation coefficient which is probably caused by clustering of segregating B atoms.
Influence of carbon on the enhanced oxygen loss in copper oxide films
Authors: Li Jian , Vizkelethy G. , Revesz P. , Mayer J. W. , Matienzo L. J. , Emmi F. , Ortega C. , Siejka J.
Published: July 2002

12C(α,α)12C, 16O(α,α)16O resonances and the 16O(3He,α)15O nuclear reaction in situ analysis have been employed to study the influence of carbon on the reduction of CuO to Cu2O. Significant oxygen loss from CuO starts in the presence of carbon at 250 °C. During in situ annealing of a CuO film, CO2 was detected by mass spectrometry. The combination of carbon and oxygen atoms to form CO2 at the carbon/copper oxide interface is the limiting step to the enhanced oxygen loss rate from CuO thin films.
Influence of trench depth on the misfit dislocation density at strained epitaxial layer interfaces grown on patterned GaAs substrates
Authors: Watson G. Patrick , Ast Dieter G. , Anderson Timothy J. , Hayakawa Yasuhiro
Published: July 2002

The number of misfit dislocations in strained, epitaxial InGaAs layers can be significantly reduced by growing on patterned substrates. Etched trenches on these substrates block misfit dislocation propagation from mesa to mesa. To determine the minimum trench depth needed to block misfit dislocations, 200 μm×200 μm mesas separated by 10-μm-wide trenches of varying depths were etched into a GaAs substrate before organometallic chemical vapor deposition of 300 or 600 nm In0.04Ga0.96As strained layers (several times the critical thickness). Three isolation regimes are seen in the 300-nm-thick InGaAs samples. The shallowest trenches, regime I, below 300 nm, do not completely block all dislocations. Misfit dislocations are blocked by trenches 300–500 nm deep, regime II, after they glide down the mesa walls and stop at the far side of the trenches. Trenches greater than 500 nm, regime III, stop dislocations at the mesa edges. The 600-nm-thick InGaAs layers with trench depths greater than 450 nm completely stopped all misfit dislocations. The third regime did not occur for trenches as deep as 650 nm. These results show that the epitaxial layer does not have to be discontinuous to prevent misfit dislocations from gliding across patterned substrates.
High electron mobility in modulation-doped Si/SiGe
Authors: Ismail K. , Meyerson B. S. , Wang P. J.
Published: July 2002

Ultrahigh-vacuum chemical vapor deposition has been exploited to grow single-heterojunction n-type modulation-doped Si/SiGe structures. Phosphorus dopant is imbedded in the SiGe layer at two distinct positions: one at the surface to prevent depletion by surface states, and the other separated from the Si heterointerface by an intrinsic SiGe spacer, to supply electrons to the two-dimensional electron gas. With a 4-nm-thick spacer layer, peak mobilities of 1800 cm2/V s, 9000 cm2/V s, and 19 000 cm2/V s were measured at room temperature, 77 and 1.4 K, respectively. These are the highest values reported for this material system.
Oxidation property of silicon small particles
Authors: Okada R. , Iijima S.
Published: July 2002

The oxidation rate of silicon small particles prepared by a gas-evaporation method and with diameters ranging from about 20 to 500 nm is investigated by high-resolution transmission electron microscopy. It is found that the oxidation rate of silicon small particles is less than the rate for wafers, and decreases with decreasing particle size. This phenomenon cannot be explained by the Deal–Grove model.
High-differential mobility of hot electrons in delta-doped quantum wells
Authors: Masselink W. Ted
Published: July 2002

Although electrons in center delta-doped AlGaAs/GaAs quantum wells have lower low-field mobilities than do electrons in uniformly doped quantum wells, experimental results presented here show that at electric fields between 2 and 4 kV/cm the differential mobility in delta-doped quantum wells rises dramatically. This large increase in differential mobility may be a result of the heating of the electrons out of the symmetric ground state into the antisymmetric first excited state. Because the excited state has a node at the delta doping, these hot electrons have a much smaller overlap with the ionized impurities of the doping spike in the well centers and therefore higher mobility.
A metal grating coupled bound-to-miniband transition GaAs multiquantum well/superlattice infrared detector
Authors: Yu Larry S. , Li Sheng S.
Published: July 2002

We report here a new metal grating coupled top illumination, bound-to-miniband transition multiple quantum well/superlattice GaAs/AlGaAs long wavelength infrared detector. By using resonant tunneling and coherent transport along the superlattice miniband, at the same time increasing the effective barrier height of the quantum well and reducing the noise-like charge transport higher energy bandwidth, a peak detectivity D* of 1.6×1010 cm√Hz/W at 8.9 μm and T= 77 K was obtained for this detector.
Multilevel YBaCuO flux transformers with high T
c SQUIDs: A prototype high T
c SQUID magnetometer working at 77 K
Authors: Oh B. , Koch R. H. , Gallagher W. J. , Robertazzi R. P. , Eidelloth W.
Published: July 2002

We have constructed optimized high Tc YBa2Cu3O7 (YBCO) multiturn flux transformers using laser-deposited films patterned with ion milling and only photolithographic masking. A five-turn flux transformer with a 0.5×0.5 mm2 pickup loop was coupled to a YBCO superconducting quantum interference device (SQUID) made on a separate substrate to demonstrate a prototype high Tc SQUID magnetometer with all components working at 77 K. There was no additional noise associated with the input coil and transformer. The magnetic field sensitivity of the 0.5×0.5 mm2 magnetometer was 3.8 pT/√Hz at 77 K and 1 kHz.
Monolithic integration of an AlGaAs/GaAs surface emitting laser diode and a photodetector
Authors: Chen Ching-Hui , Lee Si-Chen
Published: July 2002

The monolithic integration of an AlGaAs/GaAs surface emitting laser diode and a photodiode has been achieved successfully by using one step liquid phase epitaxial growth. Only a single laser beam is emitted vertically from the substrate through the nearby 45° reflector. The highest output power achieved is 22 mW and the threshold current density is 1.92 kA/cm2. The ratio between photocurrent of the detector and the output power of laser diode is 0.32 μA/mW for the type I device and 1 μA/mW for the type II device.
Scaling the Si metal-oxide-semiconductor field-effect transistor into the 0.1-μm regime using vertical doping engineering
Authors: Yan R. H. , Ourmazd A. , Lee K. F. , Jeon D. Y. , Rafferty C. S. , Pinto M. R.
Published: July 2002

Conventional scaling of the Si MOSFET into the deep submicron regime requires high substrate doping levels. This extracts a severe speed penalty, if lower standby power consumption (i.e., good subthreshold behavior) is to be maintained. We explore the scaling of fully depleted silicon-on-insulator (SOI) structures, and show, both analytically and by numerical simulation, how the horizontal leakage is controlled by vertical doping engineering. Our analysis allows different structures to be evaluated in terms of a natural length scale indicating good subthreshold behavior. Finally, we describe how retrograde doping may be used to mimic the SOI concept in bulk Si. Our results show good subthreshold behavior in the deep submicron regime can be achieved without large junction capacitance, high threshold voltage, or heavy channel doping.
Time response of a tunable-electron-density quantum well and reservoir structure
Authors: Wang Jin , Leburton J. P.
Published: July 2002

We present a theoretical model for the electron escape time from the quantum well back to the reservoir of a novel InxGa1−xAs/In1−yAlyAs multiple quantum well optical modulator. Three different mechanisms are considered: direct tunneling, phonon assisted sequential tunneling, and thermionic emission. At high forward biases, phonon assisted sequential tunneling and thermionic emission dominate, while at high reverse biases, direct tunneling from the quantum well ground state to the reservoir determines the turn-off time constant. The calculated escape time is in good agreement with the experimental data.
Ellipsometric determination of the optical constants of C60 (Buckminsterfullerene) films
Authors: Ren S. L. , Wang Y. , Rao A. M. , McRae E. , Holden J. M. , Hager T. , Wang KaiAn , Lee Wen-Tse , Ni H. F. , Selegue J. , Eklund P. C.
Published: July 2002

We report the first ellipsometric measurement of the fundamental optical constants (n,k) of C60 films deposited on Si(100) and Au overcoated Si(100) substrates. We obtain a highest occupied molecular orbital-lowest unoccupied molecular orbit (HOMO-LUMO) gap value of 2.3 eV, slightly larger than the gap values obtained from the x-ray photoelectron spectroscopy and electron-energy-loss spectroscopy experiments. The structure observed in the UV is discussed in terms of single-electron excitations across the HOMO-LUMO gap.
Room-temperature annealing of Si implantation damage in InP
Authors: Akano U. G. , Mitchell I. V. , Shepherd F. R.
Published: July 2002

Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si+ ions to doses ranging from 3.6×1011 to 2×1014 cm−2. Room-temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses ≤4×1013 cm−2, up to 70% of the initial damage (displaced atoms) annealed out over a period of ≊85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants t1<5 days and a longer t2≊100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant-induced vacancies is associated with the reordering of the InP lattice.
Negative and positive ions from radio frequency plasmas in boron trichloride
Authors: Overzet L. J. , Luo L.
Published: July 2002

The negative and positive ion mass spectra from radio frequency glow discharges in boron trichloride and 90% argon-10% boron trichloride mixtures have been investigated by amplitude modulation of the discharge excitation. The negative ion spectrum from pure boron trichloride was found to extend beyond 200 amu under most conditions even though positive ions above 120 amu were not detected under any conditions. Surprisingly, only trace signals of BCl−3 were found from the discharges, while the signals from Cl−, BCl−4, B2Cl−4, and B2Cl−5 were much larger. We were unable to detect either positive or negative ions above 120 amu from 10% boron trichloride discharges.
Optical properties of strained asymmetric triangular InGaAs/GaAs multiple quantum wells
Authors: Droopad R. , Choi K. Y. , Puechner R. A. , Shiralagi K. T. , Gerber D. S. , Maracas G. N.
Published: July 2002

We present the first report of a strained-layer asymmetric triangular In0.15Ga0.85As/GaAs multiple quantum well structure realized by molecular beam epitaxy. Low-temperature photoluminescence experiments showed that the optical efficiency of such a structure is more than five times higher than an equivalent rectangular In0.15Ga0.85As/GaAs multiple quantum well structure grown under the same conditions. This is due to an increased collection of photoexcited carriers that are being swept by the well as a result of the field formed by compositional grading and a reduction of nonradiative recombination centers.
Phonon-defect scattering in high thermal conductivity diamond films
Authors: Morelli Donald T. , Hartnett Thomas M. , Robinson Clifford J.
Published: July 2002

We have investigated the thermal conductivity of large diamond samples grown by both hot filament and microwave plasma assisted chemical vapor deposition in order to study in detail the processes limiting heat conduction in this system. For samples containing nearly 100% diamond material and no apparent defects, the thermal conductivity is consistent with that expected for polycrystalline diamond with a given crystallite size. In films prepared by the hot filament technique, we observe an additional scattering of phonons near 60 K, which we attribute to either a resonant phonon-defect interaction, or a crossover from geometrical to Rayleigh phonon-defect scattering.
Evidence for current-density-induced heating of AlGaAs single-quantum-well laser facets
Authors: Tang W. C. , Rosen H. J. , Vettiger P. , Webb D. J.
Published: July 2002

The facet temperature of AlGaAs ridge waveguided single-quantum-well lasers with various ridge widths and cavity lengths were measured as a function of output power and injection current using Raman microprobe spectroscopy. The facet temperature was found to scale with the injection current density rather than the photon flux. In addition, no large discontinuities were found below and above the lasing threshold, suggesting that the absorption of the emitted photons plays only a minor role in the facet heating. These data imply that the facet heating during the initial slow degradation regime is due to the surface nonradiative recombination of carriers and is primarily determined by the injection current density. This could be contrasted to the catastrophic optical damage regime where the lasing photons play a key role in the heating process.
Monolithically integrated InGaAlAs dielectric reflectors for vertical cavity optoelectronic devices
Authors: Kowalsky W. , Mähnss J.
Published: July 2002

Monolithically integrated dielectric reflectors have opened up a new field of optoelectronic devices. Vertical cavity lasers in the AlGaAs system are grown by MBE almost as a matter of routine. In this contribution dielectric reflectors composed of InAlAs and InGaAlAs lattice matched to InP are investigated. We achieve reflectivities of 70%, 83%, and 96% using 5, 10, and 20 periods of quarter wavelength layers. Increasing the number to 30 periods results in a maximum reflectivity exceeding 99% at a center wavelength of 1.65 μm. These experimental results indicate that vertical cavity lasers for optical communication systems in the InGaAlAs system are feasible.
Formation of ‘‘super’’ As-rich GaAs(100) surfaces by high temperature exposure to arsine
Authors: Banse B. A. , Creighton J. R.
Published: July 2002

We report that arsine exposures between 100 and 350 °C will produce ‘‘super’’ As-rich surfaces [arsenic coverages of up to ∼1.7 monolayers (ML, where 1 ML=6.26×1014 atoms cm−2)] of GaAs(100) that exhibit a c(4×4) low energy electron diffraction pattern. Temperature programmed desorption studies show that after AsD3 exposures of up to 2.6×106 L (1 L=1×10−6 Torr s) to the Ga-stabilized surface, three excess As desorption speaks are observed with maxima at 440, 480, and 570 °C. As4 desorption is detected from the lowest temperature state, while the other states desorb primarily as As2. The significance of these results for the understanding of the atomic layer epitaxy process is addressed.
Hydrogen sulfide plasma passivation of gallium arsenide
Authors: Herman J. S. , Terry F. L.
Published: July 2002

Improvement in the electrical properties of the GaAs surface has been accomplished using a room-temperature hydrogen sulfide plasma. The surface has then been protected by a 300 °C plasma enhanced chemical vapor deposition (PECVD) SiO2 film. This treatment is highly reproducible due to computer control of process parameters and long-lasting due to the SiO2 cap. Improved C-V characteristics were observed, showing interface trap densities in the high 1011 cm−2 eV−1 range. Photoluminescence (PL) measurements on the sulfided samples showed increased intensity over the untreated samples.
Subband dispersion of holes in AlAs/In0.10Ga0.90As/AlAs strained-layer quantum wells measured by resonant magnetotunneling
Authors: Lin S. Y. , Zaslavsky A. , Hirakawa K. , Tsui D. C. , Klem J. F.
Published: July 2002

Magnetotunneling of holes through the double-barrier AlAs/In0.10Ga0.90As strained-layer structure is investigated with magnetic fields up to 23 T to determine the in-plane dispersion of the two-dimensional subbands in the In0.10Ga0.90As quantum well. Mass reversal, nonparabolicity, anticrossing, and anisotropy are observed. The lack of electronlike dispersion in the lowest-energy light-hole subband is attributed to the large biaxial compressional strain in the In0.10Ga0.90As, which suppresses the mixing of heavy and light-hole states even at finite in-plane wave vectors.
K
33/K11 determination in nematic liquid crystals: An optical birefringence technique
Authors: Crawford G. P. , Mitcheltree J. A. , Boyko E. P. , Fritz W. , Zumer S. , Doane J. W.
Published: July 2002

Optical birefringence patterns of nematic liquid crystals constrained to supramicrometer capillary tubes with homeotropic anchoring are sensitive to the detailed bulk elastic properties of the nematic material. The bend-to-splay elastic constant ratio (K33/K11) is estimated by comparing the escaped-radial nematic director field observed via optical polarizing microscopy to simulated textures predicted by the Frank elastic theory.
Surface structure of hydrated amorphous silicon oxide at 3 Å resolution by scanning force microscopy
Authors: Tillmann Ralf W. , Radmacher Manfred , Gaub Hermann E.
Published: July 2002

The topology of a fully hydrated amorphous silicon oxide surface was studied with a scanning force microscope. The structure of the surface could be resolved down to 0.3 nm. The autocorrelation function of the surface relief exhibited no long range periodicity and had a glasslike character with a next neighboring repeat distance of 0.4–0.5 nm. The correlation between images obtained simultaneously from forward and backward scans was high and therefore showed that the measured surface reliefs are to a large extent independent from the local tip shape. The pair-correlation functions of subsequent images of the same surface area, however, revealed a decay over several minutes which indicates that a rearrangement of the surface may occur.
High resolution x-ray diffraction analysis of annealed low-temperature gallium arsenide
Authors: Matyi R. J. , Melloch M. R. , Woodall J. M.
Published: July 2002

High resolution x-ray diffraction methods have been used to characterize GaAs grown at low substrate temperatures by molecular beam epitaxy and to examine the effects of post-growth annealing on the structure of the layers. Double crystal rocking curves from the as-deposited epitaxial layer show well-defined interference fringes, indicating a high level of structural perfection despite the presence of excess arsenic. Annealing at temperatures from 700 to 900 °C resulted in a decrease in the perpendicular lattice mismatch between the GaAs grown at low temperature and the substrate from 0.133% to 0.016% and a decrease (but not total elimination) of the visibility of the interference fringes. Triple-crystal diffraction scans around the 004 point in reciprocal space exhibited an increase in the apparent mosaic spread of the epitaxial layer with increasing anneal temperature. The observations are explained in terms of the growth of arsenic precipitates in the epitaxial layer.
Edge effects in a gated submicron resonant tunneling diode
Authors: Beton P. H. , Dellow M. W. , Main P. C. , Foster T. J. , Eaves L. , Jezierski A. F. , Henini M. , Beaumont S. P. , Wilkinson C. D. W.
Published: July 2002

We have investigated the current-voltage [I(V)] characteristics of a gated GaAs/(AlGa)As resonant tunneling diode. As the negative gate voltage is progressively increased I(V) becomes asymmetric. In particular the peak-to-valley ratio in forward bias is decreased from ≂20 to ≂1, but in reverse bias remains constant ≂20. This arises from a lateral variation of the voltage drop across the emitter tunnel barrier, which in forward bias leads to a smearing of the resonance. We discuss the relationship between our experiment and the low peak-to-valley ratios of two-terminal submicron resonant tunneling diodes observed by other groups.
Carbon redistribution during molecular beam epitaxy of GaAs n-i-p+-i-n structures using trimethylgallium as the p-type dopant
Authors: Höfler G. E. , Baillargeon J. N. , Hsieh K. C. , Cheng K. Y.
Published: July 2002

The redistribution of carbon during molecular beam epitaxy (MBE) growth of GaAs n-i-p+-i-n structures using silicon and carbon as n-type and p-type dopants, respectively, is shown by secondary ion mass spectrometry (SIMS) analysis and electrochemical capacitance-voltage measurements. Diffusion of carbon into the surface layer is clearly observed when the carbon concentration in the p+ region exceeds ∼6×1019 cm−3. The data also shows that a significant fraction of the diffused carbon is electrically active.
Orientation relationships of epitaxial oxide buffer layers on silicon (100) for high-temperature superconducting YBa2Cu3O7−x films
Authors: Matthée Th. , Wecker J. , Behner H. , Friedl G. , Eibl O. , Samwer K.
Published: July 2002

The preparation parameters of epitaxially grown buffer layers on silicon (100) wafers were investigated. We found that an in situ removal of the native amorphous SiO2 layer from the Si surface is possible, avoiding the etching of the wafer prior to the deposition. YSZ and Y2O3 were chosen as buffer layers for subsequent YBa2Cu3O7−x thin-film deposition. The orientation of the thin films during the deposition process was analyzed by RHEED. Different orientations on the substrates are obtained depending on the evaporation parameters. TEM studies of the interfaces, x-ray diffraction analysis, and measurements of the superconducting properties were made after the deposition of the films.
Conformal deposition of WSix films on micron-sized trenches: The reactivity of film precursors
Authors: Saito T. , Shimogaki Y. , Egashira Y. , Komiyama H. , Yuyama Y. , Sugawara K.
Published: July 2002

Tungsten silicide films (WSix) were deposited from WF6 and SiH4 by low pressure chemical vapor deposition (LPCVD) using a tubular reactor system. At the deposition temperature of 150 °C, films having low concentrations of residual fluorine (∼1.5×1021 cm−3) deposited quite conformally on micron-sized trenches. The sticking probability of the film precursor was determined from the step coverage quality, as a function of deposition temperature ranging from 120 to 390 °C. While the sticking probability remained constant above 270 °C, it changed with an activation energy of 7±2 kcal/mol in the temperature range 120–240 °C. The decreased probability of sticking improved the step coverage quality at low temperatures.
In situ observation of growth rate enhancement during gas source molecular beam epitaxy of Si1−xGex alloys on Si(100) surfaces
Authors: Mokler S. M. , Ohtani N. , Xie M. H. , Zhang J. , Joyce B. A.
Published: July 2002

Using reflection-high-energy-electron-diffraction intensity oscillations the growth rate of Si1−xGex alloys at various compositions and different growth temperatures has been studied in situ. It was found that the growth rate shows a strong dependence on GeH4 flux at low temperatures (T<600 °C), while at high temperatures (T≳600 °C) the growth rate is nearly independent of the GeH4 flux but proportional to the incident Si2H6 beam flux. In addition to the enhanced growth rate, a lower activation energy is observed in the low temperature region when compared to Si homoepitaxy from Si2H6. This suggests that surface germanium atoms act as good sites for hydrogen removal which is known to inhibit Si growth from hydride sources at low temperatures. Above 600 °C, however, surface hydrogen is desorbed thermally and the addition of GeH4 has little effect on the growth rate.
Heavy carbon doping of GaAs grown by solid-source molecular-beam epitaxy
Authors: Giannini C. , Fischer A. , Lange C. , Ploog K. , Tapfer L.
Published: July 2002

We study the incorporation of carbon in GaAs at doping levels beyond 1019 cm−3 grown by conventional solid-source molecular-beam epitaxy. The correlation of Hall effect measurements at 77 and 300 K and of double crystal x-ray diffractometry allows us to determine the fraction of carbon incorporated on As sites acting as acceptors. These experiments reveal the onset of compensation at the highest doping levels of 5×1019 cm−3.
Interface roughness scattering in InAs/AlSb quantum wells
Authors: Bolognesi C. R. , Kroemer H. , English J. H.
Published: July 2002

We present a study of interface roughness scattering in not-intentionally-doped AlSb/InAs/AlSb quantum wells grown by molecular beam epitaxy on [001] GaAs semi-insulating substrates. The low-temperature mobility is found to be limited by interface roughness scattering for well widths below 100 Å. The measured mobilities are well accounted for by Gold’s theoretical treatment [A. Gold, Phys. Rev. B 35, 723 (1987)], once it is suitably modified to account for the band nonparabolicity of InAs. The experimental electron density dependence of the mobility indicates a lateral correlation length for the interface roughness Λ≊62 Å for interface fluctuations approximately 1 monolayer high. We believe this roughness scale is characteristic of the bottom (InAs-on-AlSb) interface.
Residual critical current in high T
c bicrystal grain boundary junctions
Authors: Sarnelli E. , Chaudhari P. , Lacey J.
Published: July 2002

We have recently reported on the persistence of a significant zero voltage current across bicrystal grain boundary junctions of YBa2Cu3O7−δ in an external magnetic field of several Tesla. In this note we present data on the dependence of this residual current on temperature and orientation of the grain boundary. A description of the grain boundary as being comprised of superconducting microbridges separated by normal regions is consistent with the experimental data.
Repetitive high current density pseudospark-produced ion beams
Authors: Jain K. K. , Sharma P. K.
Published: July 2002

A multigap pseudospark device filled with hydrogen or argon gas is operated up to 20 kV and ejected ion beam characteristics are experimentally investigated. The ion beam of peak current density in excess of ∼500 A/cm2 and pulse duration ∼50 ns is extracted at repetitive frequency of several tens of Hz. Results of the scaling study for the ion beam current with breakdown voltage, external capacitance, and number of insulator gaps are presented.
Structure of recrystallized silicon films prepared from amorphous silicon deposited using disilane
Authors: Hasegawa S. , Sakamoto S. , Inokuma T. , Kurata Y.
Published: July 2002

The structure of polycrystalline Si (poly-Si) films, prepared by annealing of amorphous Si films deposited using Si2H6 and SiH4, has been investigated as a function of deposition temperature Td (450–580 °C) and annealing temperature Ta (550–1000 °C). A dominant texture of the poly-Si films changed from 〈100〉 for Td below 500 °C to 〈111〉 texture for Td above 500 °C, independent of Ta. For Ta lower than 650 °C, a greater grain size was obtained by the use of Si2H6 rather than SiH4. It was suggested that the changes of these texture and grain size, respectively, are mainly controlled by Td and the deposition rate of the amorphous Si films.
Generation of dc substrate current in metal-oxide-semiconductor structures under an oscillating gate voltage
Authors: Mitra V. , Benfdila A. , Bouderbala R. , Bentarzi H.
Published: July 2002

The present letter reports the results of the experimental measurements of the dc substrate current in metal-oxide-semiconductor (MOS) structures operated under a gate-voltage signal oscillating under depletion limits. A new component has been detected in this current whose direction of flow is independent of the polarity of the applied gate voltage as well as the nature of the MOS structure. Its magnitude shows strong dependence on the frequency of the applied gate voltage, giving rise in general to three prominent peaks in the current-frequency curve. Arguments are given in support of the view that this current has its origin from the charging and discharging of the surface-states existing on the Si-SiO2 interface under non-steady-state emission.
Carrier profile evaluation for a Zn-doped InGaAsP/InGaAsP multiquantum well using a low-temperature capacitance-voltage method
Authors: Yamamoto Norio , Yokoyama Kiyoyuki , Yamamoto Mitsuo
Published: July 2002

We studied the carrier profile of a Zn-doped InGaAsP/InGaAsP multiquantum well (MQW) using capacitance-voltage (C-V) measurement. Lowering the temperature to 77 K suppresses the Debye length, allowing us to obtain a detailed carrier profile. Furthermore, we propose a method for analyzing the carrier profile, taking the exact depletion layer extension at pn junction into account. Applying the analysis, we obtained the actual carrier profile in the doped MQW with agreement between the peak position in the profile and the well position of MQW. This shows that the low-temperature C-V measurement is effective for investigating the carrier profile in MQW.
Two-color infrared photodetector using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells
Authors: Tsai K. L. , Chang K. H. , Lee C. P. , Huang K. F. , Tsang J. S. , Chen H. R.
Published: July 2002

A two-color infrared detector using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells is demonstrated. The response peak of the GaAs/AlGaAs quantum well is at 8 μm, and that of the InGaAs/AlGaAs quantum well is at 5.3 μm. The responsivity of the detector is 1 A/W at 8 μm and 0.27 A/W at 5.3 μm; these are the best values reported for a two-color quantum well infrared detectors (QWIPs) with peak sensitivities in the spectral regions of 3–5.3 μm and 7.5–14 μm. Single-colored 5.3 and 8 μm QWIPs were also fabricated to study the bias dependent behavior. This behavior can be explained using the concept of current continuity. Because of a higher electrical resistance, a high electric field domain is always formed first in the shorter wavelength quantum well stack.
Long-wavelength PtSi infrared detectors fabricated by incorporating a p+ doping spike grown by molecular beam epitaxy
Authors: Lin T. L. , Park J. S. , George T. , Jones E. W. , Fathauer R. W. , Maserjian J.
Published: July 2002

By incorporating a 1-nm-thick p+ doping spike at the PtSi/Si interface, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p+ doping spike and the Schottky image force. The p+ doping spikes were grown by molecular beam epitaxy at 450 °C using elemental boron as the dopant source, with doping concentrations ranging from 5×1019 to 2×1020 cm−3. Transmission electron microscopy indicated good crystalline quality of the doping spikes. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p+ spikes. Thermionic emission dark current characteristics were observed and photoresponses in the LWIR regime were demonstrated.
Electron transport properties of a strained Si layer on a relaxed Si1−xGex substrate by Monte Carlo simulation
Authors: Miyata H. , Yamada Toshishige , Ferry D. K.
Published: July 2002

The in-plane transport properties of a strained (100) Si layer on a relaxed Si1−xGex substrate are studied with an ensemble Monte Carlo technique. Similar velocity (-field) characteristics are found for strained Si with any valley splitting energy ΔE≥0.1 eV. These phonon-limited electron mobilities reach 4000 cm2/V s at 300 K, and 23 000 cm2/V s at 77 K. There is only a slight increase in the saturation velocity at both temperatures. However, a significant overshoot peak transient velocity is found to depend upon ΔE, and for ΔE=0.4 eV, reaches 4.1×107 cm/s at 300 K, and 5.2×107 cm/s at 77 K.
Thermally stable oxygen implant isolation of p-type Al0.2Ga0.8As
Authors: Zolper John C. , Baca Albert G. , Chalmers Scott A.
Published: July 2002

High dose oxygen implantation was used to form high resistivity regions in p-type Al0.2Ga0.8As. By achieving oxygen concentrations 30 times the grown-in beryllium concentration we created Al0.2Ga0.8As layers with a sheet resistance of over 1010 Ω/⧠ that were stable to 900 °C. Samples implanted with a base dose of 2×1014 cm−2 showed an apparent activation energy for conduction of 0.67 eV after annealing at 800 °C.
Lumped circuit model of two-dimensional to two-dimensional tunneling transistors
Authors: Katayama Y. , Tsui D. C.
Published: July 2002

A lumped circuit model for the two-dimensional (2D) to 2D tunneling transistor is proposed. A new concept of virtual separation of nodes is introduced to distinguish the energy of the subband edges and the Fermi energy of the quantum wells in the circuit diagram. The two virtually separated nodes are connected by the quantum capacitance due to the quantum confinement of the electrons in each well. This concept provides a simple and accurate representation of the device operation by the geometrical capacitances, the quantum capacitances, and the voltage dependent tunneling resistance.
Independent determination of composition and relaxation of partly pseudomorphically grown Si-Ge layers on silicon by a combination of standard x-ray diffraction and transmission electron microscopy measurements
Authors: Bugiel E. , Zaumseil P.
Published: July 2002

The concentration of Ge and the relaxation of partly pseudomorphically grown thin SiGe layers on Si can be found independently by a combination of standard x-ray double-crystal diffractometry (DCD) and transmission electron microscopy (TEM). DCD and TEM determine the lattice constant variations of the netplanes parallel and perpendicular to the surface from the angular distance between substrate and layer peak and from the average distance of misfit dislocations or the distance of Moiré fringes, respectively. The method is demonstrated for three samples with low, medium, and high Ge content.
Reactive chemical beam etching of InP inside a chemical beam epitaxial growth chamber using phosphorus trichloride
Authors: Tsang W. T. , Kapre R. , Sciortino P. F.
Published: July 2002

We have extended the capability and versatility of a chemical beam epitaxial (CBE) system by demonstrating reactive chemical beam etching (RCBE) of InP using phosphorus trichloride (PCl3) as the gaseous etching beam injected directly into the growth chamber. This permits instant switching from etching to growth (and vice versa) in the same run for the first time in CBE. We investigate RCBE of InP at various substrate temperatures between ∼400 and 580 °C, under different PCl3 fluences, and etching conditions. Excellent surface morphology was obtained at high temperatures (≳530–570 °C) and under an etching rate of ≲6 Å/s. We also found that upon addition of trimethylindium flow equivalent to a growth rate of 1 Å/s during RCBE a dramatic improvement in surface morphology was obtained even at a high net etching rate of 10 Å/s. The surface morphology obtained under such conditions is indistinguishable from that of the original substrate surface.
Atomic-force-microscopic study of heteroepitaxial diamond nucleation on (100) silicon
Authors: Jiang X. , Schiffmann K. , Westphal A. , Klages C.-P.
Published: July 2002

To understand the mechanism of heteroepitaxial diamond growth, the early stage of diamond nucleation, generated in a microwave plasma on negatively biased single crystalline (100) silicon substrates, was observed by atomic force microscopy. The results show that nonfacetted nuclei are initially formed whose size increases with deposition time. Reflection high energy electron diffraction reveals that the nuclei are of crystalline structure in spite of their very small height of about 5 nm. A critical radius of the nuclei rc seems to exist under conditions applied in this study. The initial nuclei have a preferential (100) orientation. By a proper control of the nucleation and growth process, however, one can allow the epitaxially generated nuclei to reach rc and to grow larger.
Fabrication of silicon nanostructures with a scanning tunneling microscope
Authors: Snow E. S. , Campbell P. M. , McMarr P. J.
Published: July 2002

A technique is presented for fabricating Si nanostructures with a scanning tunneling microscope operated in air. The process involves the direct chemical modification of a H-passivated Si(100) surface and a subsequent liquid etch. The chemically modified portions of the surface can withstand a deep (≳100 nm) liquid etch of the unmodified regions with no etch degradation of the modified surface. At a write speed of 1–10 μm/s, large-area (50 μm×50 μm) patterns with lateral feature sizes ∼25 nm are reliably fabricated.
Direct imaging of dopants in GaAs with cross-sectional scanning tunneling microscopy
Authors: Johnson M. B. , Albrektsen O. , Feenstra R. M. , Salemink H. W. M.
Published: July 2002

We report the direct imaging of individual electrically active dopants on cross-sectionally cleaved GaAs using scanning tunneling microscopy and compare these results to theory. The observation of these dopants is due to an enhancement in the tunneling current in the neighborhood of an ionized dopant atom in the top several surface layers. In highly p-doped GaAs, for tunneling out of the valence band, the dopants in the top several surface layers appear as individual circular hillocks about 2 nm in diameter, superimposed on the As sublattice, as expected. From the size of the hillock and the symmetry of the As sublattice enhanced by the hillock one can infer whether the dopant lies in the top, second or deeper layers.
New leakage mechanism in sub-5-nm oxynitride dielectrics
Authors: Nguyen Tue , Carl Daniel A. , Nguyen Son V. , Dobuzinsky David M. , Korejwa Josef W.
Published: July 2002

Conduction current in thin (3.5–6.5 nm) oxynitride dielectrics prepared by rapid thermal annealing of SiO2 films in NH3 ambient at high temperature (1100 °C) is studied. Significantly high leakage currents at low fields and independent of temperatures has been observed in films with thickness of 4.5 nm or less. The enhanced conduction is proposed to be direct tunneling current via electron traps located in the dielectric film. This new leakage mechanism in sub-5-nm oxynitride dielectric is different from the thicker (5.5 nm or higher) films where the conduction is only slightly enhanced and is temperature dependent. This leakage mechanism could open new applications where significant tunneling current are needed for thicker (<5 nm) films.
Interfacial alloy formation in ZnSe/CdSe quantum-well heterostructures characterized by photoluminescence spectroscopy
Authors: Zhu Ziqiang , Yoshihara Hiroteru , Takebayashi Kazuhisa , Yao Takafumi
Published: July 2002

The interface of a binary single quantum-well (SQW) structure of ZnSe/CdSe, where CdSe less than one monolayer is sandwiched by ZnSe layers (submonolayer SQW), is characterized by photoluminescence spectroscopy. The dependence of the energy, linewidth, and intensity of excitonic emission from submonolayer SQWs on the well thickness of CdSe is extensively investigated. The characteristics of the excitonic emission are interpreted in terms of alloy formation at the interface.
Erratum: ‘‘Epitaxial bcc FexCo1−x alloy films on ZnSe(001)’’ [Appl. Phys. Lett. 61, 2476 (1992)]
Authors: Gutierrez C. J. , Krebs J. J. , Prinz G. A.
Published: July 2002

In Fig. 2, the units given are incorrect. The proper units for K1 are ‘‘105 erg/cm3’’; not ‘‘erg/cm2’’ as given. The same error in units is found in the discussion of ‖Ku‖ at the end of the second paragraph before the summary. These errors do not affect the conclusions.
Use of high T
c superconducting electrodes for lead lanthanum zirconium titanate ceramics
Authors: Hsi Chi-Shiung , Haertling Gene H. , Furman Eugene
Published: July 2002

Lead lanthanum zirconium titanate (PLZT) 9.5/65/35 samples were electroded with BSCCO and YBCO superconductor materials. Extensive interaction was obtained between the PLZT and the YBCO, and very low interaction was observed between the BSCCO and the PLZT. The BSCCO superconductor on the PLZT substrate maintained its superconducting properties at liquid nitrogen temperature. The apparent dielectric constant of the PLZT was influenced by the electroding materials. Domain switching was found to be influenced by the electrode materials at low temperature. The BSCCO electroded samples showed the highest polarization switching rate among the samples electroded by different materials.
Polarization modulation of cruciform vertical-cavity laser diodes
Authors: Choquette Kent D. , Lear K. L. , Leibenguth R. E. , Asom M. T.
Published: July 2002

We demonstrate electrical switching and modulation between two orthogonal polarization modes of air-post vertical-cavity surface emitting lasers with cruciform transverse cavity geometry. The continuous-wave lasing emission is switched from one polarization mode to the orthogonal mode at frequencies up to 50 MHz by a small signal modulation of the injection current. Furthermore, a polarized output signal at twice the input frequency is generated at frequencies up to 10 MHz by a large signal modulation of the injection current from below threshold to above the polarization switching transition.