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1 Dec 1997

Volume 71, Issue 22, pp. 3191-3307

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Is the c(4×4) reconstruction of Si(001) associated with the presence of carbon?

Kazushi Miki, Kunihiro Sakamoto, and Tsunenori Sakamoto

Appl. Phys. Lett. 71, 3266 (1997); http://dx.doi.org/10.1063/1.120308 (3 pages) | Cited 33 times

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With the increasing annealing temperature in ultrahigh vacuum, hydrogen-terminated Si(001) surface exhibit a (1×2) reconstruction around 500 °C, c(4×4) in the narrow range of 580–750 °C, and a weak SiC transmission pattern above 750 °C. The simultaneous disappearance of c(4×4) and the appearance of the SiC pattern suggest that the c(4×4) reconstruction is associated with carbon contamination. The carbon concentration of 2.5×1018 atoms/cm3 is insufficient for carbon atoms to be a component of the c(4×4) structure, and therefore the carbon must be having another effect. A consequence of this conclusion is that carbon is not responsible for C-type defects. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena
61.72.Cc Kinetics of defect formation and annealing

Auger recombination in 4H-SiC: Unusual temperature behavior

A. Galeckas, J. Linnros, V. Grivickas, U. Lindefelt, and C. Hallin

Appl. Phys. Lett. 71, 3269 (1997); http://dx.doi.org/10.1063/1.120309 (3 pages) | Cited 27 times

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The band-to-band Auger recombination in 4H-SiC material is studied using a time-resolved photoinduced absorption technique. The Auger recombination coefficient is derived from the kinetics of electron-hole plasma in heavily doped n-type 4H-SiC and in low-doped 4H-SiC epitaxial layers in the temperature interval 300–565 K. Within this range, its value decreases from γ3 = (7±1)×10−31 cm6 s−1 to γ3 = (4±1)×10−32 cm6 s−1. The observed pronounced reduction of Auger recombination rate with temperature is correlated to temperature dependent threshold energy of Auger process. © 1997 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Mx High-frequency effects; plasma effects
78.66.Li Other semiconductors
79.20.Fv Electron impact: Auger emission
78.47.-p Spectroscopy of solid state dynamics

Comparison of trimethylgallium and triethylgallium for the growth of GaN

A. Saxler, D. Walker, P. Kung, X. Zhang, M. Razeghi, J. Solomon, W. C. Mitchel, and H. R. Vydyanath

Appl. Phys. Lett. 71, 3272 (1997); http://dx.doi.org/10.1063/1.120310 (3 pages) | Cited 9 times

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GaN films grown by low-pressure metalorganic chemical vapor deposition using trimethylgallium and triethylgallium as gallium precursors are compared. The films were characterized by x-ray diffraction, Hall effect, photoluminescence, secondary ion mass spectroscopy, and etch pit density measurements. GaN layers grown using triethylgallium exhibited superior electrical and optical properties and a lower carbon impurity concentration. © 1997 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Simultaneous mapping of bulk and surface recombination in silicon

Hans-Christoph Ostendorf and Arthur L. Endrös

Appl. Phys. Lett. 71, 3275 (1997); http://dx.doi.org/10.1063/1.120311 (3 pages) | Cited 7 times

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A method is presented which allows a fast, nondestructive, and laterally resolved separation of bulk and surface recombination of silicon samples. The method works without any assumptions on the values of diffusion length and surface recombination velocity. No special sample processing is necessary prior to the measurement. An extended Monte Carlo based sensitivity analysis shows that diffusion lengths below the sample thickness can be determined with an accuracy better than ±20%. The detection range for the surface recombination velocity is 102–105 cm/s with a maximum uncertainty of a factor of 2. Experimental data are presented that prove the applicability of the new scheme. © 1997 American Institute of Physics.  
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors

Is the arsenic incorporation kinetics important when growing GaAs(001), (110), and (111)A films?

E. S. Tok, T. S. Jones, J. H. Neave, J. Zhang, and B. A. Joyce

Appl. Phys. Lett. 71, 3278 (1997); http://dx.doi.org/10.1063/1.120312 (3 pages) | Cited 18 times

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The incorporation coefficients of As2 and As4, obtained from reflection high-energy electron diffraction intensity oscillations in the As-limited growth regime, are compared for the growth of GaAs on (001), (110), and (111)A surfaces by molecular beam epitaxy. The kinetic results are remarkably similar for (110) and (111)A, but very different from those obtained on (001). The incorporation coefficients decrease with increasing temperature for all three surfaces, with the effect being much more dramatic on (110) and (111) A. The low- and temperature-dependent incorporation coefficients on (110) and (111)A explain the need for high As:Ga flux ratios and low substrate temperatures in the preparation of high-quality GaAs epitaxial layers. © 1997 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Low-threshold quasi-cw type-II quantum well lasers at wavelengths beyond 4 μm

Chih-Hsiang Lin, S. S. Pei, H. Q. Le, J. R. Meyer, and C. L. Felix

Appl. Phys. Lett. 71, 3281 (1997); http://dx.doi.org/10.1063/1.120313 (3 pages) | Cited 8 times

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Optically pumped InAs/InGaSb/InAs/AlSb type-II quantum well lasers emitting from 4.1 to 4.36 μm were operated up to 226 K with a characteristic temperature T0 of 30 K. The absorbed threshold pump intensity at 0.98 μm was 0.12 kW/cm2 at 100 K, and 3.25 kW/cm2 at 200 K with a pulse length of 5 μs and a repetition rate of 2 kHz. At 73 K, the peak output power was 250 mW per facet with a pulse length of 10 μs and a repetition rate of 10 kHz. A cw output power of 14.7 mW was observed at 74 K. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Photoinduced hole-doping effect in (Y0.5Ca0.5)Ba2Cu3Oδ films

C. L. Lin, Y. K. Lin, C. C. Chi, W. Y. Guan, and M. K. Wu

Appl. Phys. Lett. 71, 3284 (1997); http://dx.doi.org/10.1063/1.120323 (3 pages) | Cited 1 time

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The persistent photoinduced changes in the critical temperature TC and the normal state conductivity of (Y0.5Ca0.5)Ba2Cu3Oδ thin films are studied. Previously such effects have been observed only in underdoped YBa2Cu3Oδ or YSrxBa2−xCu3Oδ, which always lead to the enhancement of both TC and conductivity. The current system can be doped from the underdoped regime to the overdoped regime by increasing its oxygen content. The photoinduced TC reduction in the overdoped films is observed. The simultaneous enhancement of conductivity is consistent with the interpretation that photoillumination always increases hole concentration in the “123” systems. © 1997 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.62.Dh Effects of crystal defects, doping and substitution
73.50.Pz Photoconduction and photovoltaic effects
74.10.+v Occurrence, potential candidates

Current carrying capability of multifilamentary (BiPb)2Sr2Ca2Cu3Ox tapes determined from transport and magnetization measurements

C. Reimann, O. Waldmann, P. Müller, M. Leghissa, and B. Roas

Appl. Phys. Lett. 71, 3287 (1997); http://dx.doi.org/10.1063/1.120314 (3 pages) | Cited 17 times

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The magnetic field dependence of the critical current IC(B) and the remanent magnetization of several multifilamentary (BiPb)2Sr2Ca2Cu3Ox tapes were measured. The low field behavior of IC(B) is interpreted by the self-field effect, whereas at higher fields, the field dependence for all tapes was found to be identical except for a constant factor. Although self-field transport critical current densities jC0 differed widely for the tapes, the intergranular critical current densities determined from remanent magnetization were found to be equal. The results indicate that the reduction of jC0 by macroscopic defects is an important factor, whereas locally the filaments are of high quality. © 1997 American Institute of Physics.
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74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents

Magnetic properties and magnetic domain structures of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx

Jinbo Yang, Weihua Mao, Benpei Cheng, Yingchang Yang, Hai Xu, Baoshan Han, Senlin Ge, and Wanjun Ku

Appl. Phys. Lett. 71, 3290 (1997); http://dx.doi.org/10.1063/1.120315 (3 pages) | Cited 13 times

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We succeed in preparing anisotropic magnetic powders with high performance based on the NdFe10.5Mo1.5Nx nitrides. The properties of these materials are favorable for permanent magnet application. The domain structures of the NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx were studied by using magnetic force microscopy. Upon nitrogenation, a domain structure transition from complex maze to simple stripe was found. This transition is due to the strongly uniaxial magnetocrystalline anisotropy induced by interstitial nitrogen atoms. Together with magnetic measurements, we have calculated the domain wall energy γ, exchange constant A, domain wall thickness δ, and critical single-domain particle size Dc of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx. © 1997 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys
75.50.Ww Permanent magnets

Improved spatial resolution in magnetic force microscopy

George D. Skidmore and E. Dan Dahlberg

Appl. Phys. Lett. 71, 3293 (1997); http://dx.doi.org/10.1063/1.120316 (3 pages) | Cited 38 times

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Electron beam deposited spikes for use in magnetic force microscopy have been grown onto atomic force microscope tips and coated with magnetic thin films using thermal evaporation. The resulting magnetically active regions are a close approximation to monopoles or dipoles located on the very end of the spikes. We show that these tips image with increased spatial resolution and less sample perturbation than the standard, commercially available tips. © 1997 American Institute of Physics.
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07.79.Pk Magnetic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Magnetic tunnel junctions with in situ naturally-oxidized tunnel barrier

H. Tsuge and T. Mitsuzuka

Appl. Phys. Lett. 71, 3296 (1997); http://dx.doi.org/10.1063/1.120317 (3 pages) | Cited 33 times

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Al/Fe/Al2O3/CoFe/Al junctions with dimensions of 2×2–40×40 μm2 were prepared on a 2 in. Si wafer using conventional photolithography and ion-beam etching. The junction trilayers were deposited sequentially without breaking vacuum and a tunnel barrier was in situ naturally oxidized. The resultant junction resistance scaled linearly with the junction area over all dimensions used. Normalized resistance of less than 1.5×10−5 Ω cm2 was obtained in maintaining a magnetoresistance (MR) ratio of about 5%. The resistance values are much smaller than ever reported and close to those required for an MR head device. The MR ratio exhibited no significant change up to at least 1×103 A/cm2 with increasing junction current density. © 1997 American Institute of Physics.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.At Metal and metallic alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.40.Rw Metal-insulator-metal structures
81.65.Cf Surface cleaning, etching, patterning

Contribution of current perpendicular to the plane to the giant magnetoresistance of laterally modulated spin values

A. Encinas, F. Nguyen Van Dau, M. Sussiau, A. Schuhl, and P. Galtier

Appl. Phys. Lett. 71, 3299 (1997); http://dx.doi.org/10.1063/1.120318 (3 pages) | Cited 7 times

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Giant magnetoresistance (GMR) effects up to 10% have been observed in Co/Cu/FeNi spin valve structures grown onto step bunched vicinal Si(111) substrates misoriented towards [11-2]. The step bunching is activated using a simple thermal treatment which leads to surfaces where terraces alternate with facets at the nanometer scale. GMR of the spin valve structures is investigated with the current applied parallel or perpendicular to the steps. An in-plane uniaxial magnetic anisotropy is induced in each magnetic layer with the easy axis parallel to the steps. This results in square GMR behavior when the field is applied along the easy axis. Specific features observed when the field is applied along the hard axis are also shown to be the consequence of this anisotropy. When the initial misorientation angle of the substrate becomes higher than 4°, we observe an enhancement of the room-temperature GMR when the current is applied perpendicular to the steps. The origin of this enhancement is discussed based on the temperature dependence of this effect. © 1997 American Institute of Physics.
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75.47.De Giant magnetoresistance
75.30.Gw Magnetic anisotropy
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.At Metal and metallic alloys

Charging of substrates irradiated by particle beams

P. N. Guzdar, A. S. Sharma, and S. K. Guharay

Appl. Phys. Lett. 71, 3302 (1997); http://dx.doi.org/10.1063/1.120319 (3 pages) | Cited 10 times

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A simple dynamical model for studying the charging of substrates irradiated by particle beams is developed. The charging potential for positive ion beams can be as large as the beam voltage. For negative ion beams, the charging potential is significantly lower and is governed by the secondary electrons. A closed form expression derived for the charging voltage in the case of negative ion beams agrees well with our numerical work. The results are consistent with observations on charging of isolated substrates during ion implantation with positive and negative ion beams. © 1997 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.80.Jh Ion radiation effects

Determination of the energy diagram of the dithioketopyrrolopyrrole/SnO2:F heterojunction by surface photovoltage spectroscopy

Ellen Moons, Martin Eschle, and Michael Grätzel

Appl. Phys. Lett. 71, 3305 (1997); http://dx.doi.org/10.1063/1.120322 (3 pages) | Cited 4 times

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The work functions of solid layers of various thicknesses of dithioketopyrrolopyrrole (DTPP), evaporated on SnO2:F, were measured by the Kelvin probe technique. Surface photovoltage (SPV) measurements confirm the p-conductivity type. By front and back side illumination of the thick DTPP layers, two space-charge layers are distinguished, allocated to the air/DTPP and DTPP/SnO2:F interface, respectively. The SPV of thinner layers is a superposition of the front side signal and back side signal, modulated by a filter effect through the organic layer. This permitted the construction of the energy diagram of the DTPP/SnO2:F junction. © 1997 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Pz Photoconduction and photovoltaic effects
72.80.Le Polymers; organic compounds (including organic semiconductors)
73.30.+y Surface double layers, Schottky barriers, and work functions
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