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11 Apr 1988

Volume 52, Issue 15, pp. 1201-1278

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Measurements of room‐temperature band‐gap‐resonant optical nonlinearities of GaAs/AlGaAs multiple quantum wells and bulk GaAs

S. H. Park, J. F. Morhange, A. D. Jeffery, R. A. Morgan, A. Chavez‐Pirson, H. M. Gibbs, S. W. Koch, N. Peyghambarian, M. Derstine, A. C. Gossard, J. H. English, and W. Weigmann

Appl. Phys. Lett. 52, 1201 (1988); http://dx.doi.org/10.1063/1.99157 (3 pages) | Cited 63 times

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We present a systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs multiple quantum wells (MQW’s) at room temperature and compare them with bulk GaAs. The maximum change in the refractive index is greatest for the MQW’s with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 Å MQW.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.30.Fs III-V and II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Laser desorption of polymer in a plasma reactor

W. Holber, D. Gaines, C. F. Yu, and R. M. Osgood

Appl. Phys. Lett. 52, 1204 (1988); http://dx.doi.org/10.1063/1.99158 (3 pages)

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Low‐power ultraviolet (350 nm) laser light has been used to inhibit polymer formation on silicon in a plasma reactor containing CF4 /H2 reactants. The resultant increase in etch rate has been studied as a function of hydrogen partial pressure. Auger electron spectroscopy reveals a reduction in polymer formation in the area illuminated by the laser.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
79.20.Ds Laser-beam impact phenomena
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
52.40.Hf Plasma-material interactions; boundary layer effects

Brittle‐to‐ductile transition in laser‐induced spall at ultrahigh strain rate in 6061‐T6 aluminum alloy

I. Gilath, S. Eliezer, M. P. Dariel, and L. Kornblit

Appl. Phys. Lett. 52, 1207 (1988); http://dx.doi.org/10.1063/1.99159 (3 pages) | Cited 16 times

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Experimental confirmation is provided for a brittle‐to‐ductile transition of the spall failure mode in a 6061‐T6 aluminum alloy, at a strain rate of 107 s−1 , caused by laser‐induced shock waves. This result is consistent with the prediction of a theory that has been put forward recently by Grady. The experimental approach that was used allowed determination of the maximum elongation associated with the spall failure in the alloy and pure aluminum.
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62.50.-p High-pressure effects in solids and liquids
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Elimination of secondary defects in As‐implanted Si by high concentration oxygen atoms

M. Tamura, M. Horiuchi, T. Ito, and T. Abe

Appl. Phys. Lett. 52, 1210 (1988); http://dx.doi.org/10.1063/1.99160 (3 pages) | Cited 4 times

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Arsenic precipitate‐induced dislocation loops generated at the projected range Rp of As in high‐dose As‐implanted, annealed (100) Si are eliminated, if oxygen‐atom concentrations at the Rp region are high, i.e., above about 1×1020 atoms/cm3 . This is confirmed by the following two experiments: 80 keV, 2×1016 As+/cm2, 18‐nm‐thick through‐oxide implantation together with subsequent annealing and a double implantation of 80 keV, 2×1016 As+ /cm2 and 22 keV, 5×1015 O+ /cm2 , followed by an annealing sequence. Experimental results suggest that the bonding of several As atoms with one oxygen atom suppresses As clustering.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.72.uf Ge and Si
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Radiation‐enhanced diffusion of Au in amorphous Si

F. Priolo, J. M. Poate, D. C. Jacobson, J. Linnros, J. L. Batstone, and S. U. Campisano

Appl. Phys. Lett. 52, 1213 (1988); http://dx.doi.org/10.1063/1.99161 (3 pages) | Cited 23 times

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The radiation‐enhanced diffusion of implanted Au markers in amorphous Si has been measured in the temperature range 77–693 K. Samples were irradiated with 2.5 MeV Ar ions. The diffusion coefficients show three well‐defined regions. For temperatures <400 K, diffusion is athermal and due to ballistic mixing. For temperatures in the range 400–700 K diffusion is Arrhenius‐type with an activation energy of 0.37 eV and is considerably enhanced over the normal thermal diffusion. The defects that cause the enhanced diffusion come from nuclear energy loss processes. Thermal diffusion, with an activation energy of 1.42 eV, dominates at temperatures greater than 750 K.
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66.30.J- Diffusion of impurities
61.80.Jh Ion radiation effects
61.72.uf Ge and Si

Epitaxial growth of GaAs/NiAl/GaAs heterostructures

T. Sands, J. P. Harbison, W. K. Chan, S. A. Schwarz, C. C. Chang, C. J. Palmstrøm, and V. G. Keramidas

Appl. Phys. Lett. 52, 1216 (1988); http://dx.doi.org/10.1063/1.99162 (3 pages) | Cited 38 times

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Epitaxial GaAs/NiAl/GaAs heterostructures consisting of buried NiAl layers and GaAs overlayers that are monocrystalline and well aligned have been fabricated by a combination of solid‐phase reactions and molecular beam epitaxy. The structures have been characterized by reflection high‐energy electron diffraction, electron microscopy, and ion channeling. The achievement of these stable and epitaxial buried‐metal heterostructures makes possible the fabrication of metal‐base and permeable‐base transistors, buried interconnects, and buried ground planes.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Np Solid phase epitaxy; growth from solid phases
68.35.B- Structure of clean surfaces (and surface reconstruction)

Zinc‐enhanced beryllium redistribution in GaAs/GaAlAs grown by molecular beam epitaxy

P. A. Houston, F. R. Shepherd, A. J. SpringThorpe, P. Mandeville, and A. Margittai

Appl. Phys. Lett. 52, 1219 (1988); http://dx.doi.org/10.1063/1.99163 (3 pages) | Cited 17 times

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A study of the effect of zinc diffusion into beryllium‐ and silicon‐doped GaAs/Ga0.7Al0.3As structures has been carried out. The beryllium dopant was found to diffuse very rapidly as a result of the presence of diffusing zinc, while the silicon remained unaffected. A mechanism is proposed whereby competition for the gallium sites causes the beryllium to move interstitially wherever zinc is present.
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66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Resistivity of boron‐doped polycrystalline silicon

M. Y. Ghannam and R. W. Dutton

Appl. Phys. Lett. 52, 1222 (1988); http://dx.doi.org/10.1063/1.99164 (3 pages) | Cited 5 times

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The doping dependence of the resistivity of polycrystalline silicon deposited by low‐pressure chemical vapor deposition and implanted with boron is investigated. At doping concentrations <1018 cm−3, the resistivity is almost two orders of magnitude larger than that of crystalline silicon. At very large doping levels (=1020 cm−3), the resistivity is comparable to that of crystalline silicon though slightly higher. Boron segregation at grain boundaries is not observed for doping levels <1019 cm−3. At 1020 cm−3, boron segregation or additional clustering at grain boundaries causes a reversible change in the resistivity upon changing the annealing temperature.
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73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Multilayer metallization structures with titanium nitride and titanium silicide prepared by multipulse laser irradiation

V. Craciun, I. N. Mihailescu, I. Ursu, F. Craciunoiu, A. Corici, G. Leggieri, A. Luches, V. Nassisi, and M. Martino

Appl. Phys. Lett. 52, 1225 (1988); http://dx.doi.org/10.1063/1.99674 (3 pages) | Cited 10 times

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We synthesized titanium nitride and titanium silicide layers on silicon by only one‐step multipulse laser irradiation of titanium‐coated silicon wafers in a jet of nitrogen, with characteristics appropriate for utilization in metallization schemes with very large scale integration devices.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Ls Metallization, contacts, interconnects; device isolation

Space‐charge buildup and bistability in resonant‐tunneling double‐barrier structures

F. W. Sheard and G. A. Toombs

Appl. Phys. Lett. 52, 1228 (1988); http://dx.doi.org/10.1063/1.99165 (3 pages) | Cited 73 times

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Using the sequential theory of resonant tunneling, the dc current‐voltage characteristic of a double‐barrier structure is calculated, taking into account the effect of space charge in the quantum well. A region of current bistability is found over a voltage range which is determined by the maximum space charge and the capacitance of the structure. These parameters are directly related to the periodicity of magnetoquantum oscillations in the current.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Manipulation of nucleation sites and periods over amorphous substrates

T. Yonehara, Y. Nishigaki, H. Mizutani, S. Kondoh, K. Yamagata, T. Noma, and T. Ichikawa

Appl. Phys. Lett. 52, 1231 (1988); http://dx.doi.org/10.1063/1.99675 (3 pages) | Cited 18 times

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A selective nucleation based crystal growth technique over amorphous substrates is originated. The method manipulates nucleation sites and periods, and hence, controls the grain boundary location by modifying the substrate surface. In Si, Si3 N4 provides artificial nucleation sites, 1–2 μm in diameter, 100 μ m in period, which is surrounded by SiO2 . One Si nucleus is formed exclusively in a small portion of Si3 N4 . The highly faceted and periodically located nuclei grow over SiO2 up to 100 μm in diameter before impingement. A field‐effect transistor fabricated inside the island operates comparably to the bulk Si control.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
85.30.Tv Field effect devices
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Effect of copper related defects on the electron transport properties of semi‐insulating CdSe

M. Roth and A. Burger

Appl. Phys. Lett. 52, 1234 (1988); http://dx.doi.org/10.1063/1.99166 (3 pages) | Cited 2 times

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Semi‐insulating CdSe crystals with a reduced concentration of electron trapping centers have been grown and characterized. The existence of complex electron traps is attributed to the presence of trace copper impurity. The trap density, trap level depth, trapping time, cross section for trapping of electrons, and the electron mobility have been determined for the first time on one single CdSe crystal using the combination of space‐charge‐limited currents (SCLC’s) method, standard nuclear measurements, and the transient charge technique (TCT). The advantages for applications of semi‐insulating CdSe as a novel material for spectrometer grade nuclear radiation detectors are emphasized.
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71.55.Gs II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Reduction in the concentration of DX centers in Si‐doped GaAlAs using the planar doping technique

B. Etienne and V. Thierry‐Mieg

Appl. Phys. Lett. 52, 1237 (1988); http://dx.doi.org/10.1063/1.99167 (3 pages) | Cited 30 times

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Whereas the concentration of DX centers in Si‐doped GaAlAs is nearly independent of the molecular beam epitaxy growth conditions when conventional bulk doping is used, we have discovered that it can be strongly reduced in the case of planar doping. Most interesting is the fact that this reduction is more effective at a high doping level. At an electron density of 2×1013 cm−2 per doping plane [3% of the atomic density of a (100) oriented GaAlAs surface] we observe a nearly complete disappearance of these centers. A possible origin of this unexpected effect is proposed.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Mechanisms of doping‐enhanced superlattice disordering and of gallium self‐diffusion in GaAs

T. Y. Tan and U. Gösele

Appl. Phys. Lett. 52, 1240 (1988); http://dx.doi.org/10.1063/1.99168 (3 pages) | Cited 131 times

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Recently available Ga‐Al interdiffusion results in GaAs/AlAs superlattices allow us to conclude that Ga self‐diffusion in GaAs is carried by triply negatively charged Ga vacancies under intrinsic and n‐doping conditions. The mechanism of the Si‐enhanced superlattice disordering is the Fermi‐level effect which increases the concentrations of the charged point defect species. For the effect of the p dopants Be and Zn, the Fermi‐level effect has to be considered together with dopant diffusion induced Ga self‐interstitial supersaturation or undersaturation. Self‐diffusion of Ga in GaAs under heavy p‐doping conditions is governed by positively charged Ga self‐interstitials.
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68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.J- Diffusion of impurities
66.30.H- Self-diffusion and ionic conduction in nonmetals

Laser‐induced homoepitaxial growth of gallium arsenide films

Shirley S. Chu, T. L. Chu, C. L. Chang, and H. Firouzi

Appl. Phys. Lett. 52, 1243 (1988); http://dx.doi.org/10.1063/1.99169 (3 pages) | Cited 12 times

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Epitaxial gallium arsenide films have been deposited on single crystalline GaAs substrates of (100) orientation at 425–500 °C by ArF excimer laser‐induced metalorganic chemical vapor deposition. The important process parameters include the cleanliness of the substrate surface, substrate temperature, the composition, flow rate, pressure of the reaction mixture, and the pulse energy and pulse rate of the laser. Particular attention was directed to the in situ cleaning of the substrate surface prior to the deposition process. When the AsH3/(CH3)3Ga molar ratio in the reaction mixture exceeds 10, the deposited films have a specular mirror surface and show no structural features under a scanning electron microscope. Their single crystallinity has been confirmed by transmission electron microscopy. The carrier concentration decreases with increasing AsH3/(CH3)3Ga molar ratio and with decreasing substrate temperature, as expected. The carbon concentration in the deposited films, determined by secondary ion mass spectrometry, is in the range of 5×1017 to 2×1018 cm−3.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
73.61.Ey III-V semiconductors

Fabrication of gatable submicron channels in AlxGa1−xAs‐GaAs heterostructures

K. Owusu‐Sekyere, A. M. Chang, and T. Y. Chang

Appl. Phys. Lett. 52, 1246 (1988); http://dx.doi.org/10.1063/1.99170 (3 pages) | Cited 6 times

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A new, simplified process has been developed for fabricating submicron AlxGa1−xAs‐GaAs heterostructure devices for low‐temperature transport studies, with the advantage of gatability. This process utilizes electron beam lithography, photolithography, and wet etching techniques to laterally confine the two‐dimensional electron gas, and possesses the unique feature that the metal etch mask for the electron beam defined narrow section is deposited directly on top of the heterostructure surface, allowing for use as a gate. Devices of lithographic widths from 0.4 to 2.0 μm have been successfully fabricated, where the 0.4 μm devices of both enhancement and depletion modes have been demonstrated to function down to 0.35 K in temperature.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer

Pseudomorphic ZnSe/n‐GaAs doped‐channel field‐effect transistors by interrupted molecular beam epitaxy

G. D. Studtmann, R. L. Gunshor, L. A. Kolodziejski, M. R. Melloch, J. A. Cooper, R. F. Pierret, D. P. Munich, C. Choi, and N. Otsuka

Appl. Phys. Lett. 52, 1249 (1988); http://dx.doi.org/10.1063/1.99171 (3 pages) | Cited 32 times

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The fabrication and current‐voltage characteristics of the first depletion‐mode field‐effect transistors based on a pseudomorphic ZnSe/n‐GaAs heterointerface are described. The devices are doped‐channel field‐effect transistors produced by means of interrupted growth with the use of two separate molecular beam epitaxy systems. Very strong (visible to the naked eye) reflection high‐energy electron diffraction intensity oscillations persist for 120 periods when ZnSe is nucleated on the GaAs epilayer. The current‐voltage characteristics of the transistors are close to ideal; channel modulation indicates that the Fermi level is not pinned at the ZnSe/GaAs interface.
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85.30.Tv Field effect devices
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.De Semiconductor-device characterization, design, and modeling

Ballistic electron transport across collector barriers in AlGaAs/GaAs hot‐electron transistors

M. Kuzuhara, K. Kim, D. Arnold, and K. Hess

Appl. Phys. Lett. 52, 1252 (1988); http://dx.doi.org/10.1063/1.99172 (3 pages) | Cited 4 times

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A Monte Carlo calculation has been performed to simulate the experiment of Heiblum and co‐workers [Phys. Rev. Lett. 55, 2200 (1985)], regarding ballistic electron transport and the electron transit time across the AlGaAs collector barrier region in AlGaAs/GaAs tunneling hot‐electron transfer amplifier devices. Ballistic transport is proven to be highly probable across a 1000‐Å‐thick collector barrier under retarding field and hot‐electron injection conditions at 4.2 K. Applying accelerating fields in the barrier results in almost negligible ballistic fraction of the transmitted hot electrons because of electron scattering into the satellite valleys. This result seems paradoxical at first sight. However, it is typical for electronic transport in heterolayers and fully consistent with the interpretation of the experiments by Heiblum and co‐workers. There exists a negative collector‐base bias range which minimizes the collector barrier transit time, corresponding to the condition of large ballistic probability and simultaneously relatively little deceleration of the electrons by the applied retarding field.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Observation of charge‐separating defects in HgCdTe using remote contact electron beam induced current

L. O. Bubulac and W. E. Tennant

Appl. Phys. Lett. 52, 1255 (1988); http://dx.doi.org/10.1063/1.99173 (3 pages) | Cited 17 times

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A spatially resolved electron beam technique, remote contact electron beam induced current, has been developed to detect and map charge‐separating defects in HgCdTe with two remote sample contacts. This technique, characterized by a high spatial resolution, ∼1 μm, and a high sensitivity (signal/noise) to fields produced by inclusions, damage, dislocations, strain, p‐n junctions, and possibly compositional (band gap) and doping variations, shows promise for analyzing materials, passivation coatings, and diode arrays without making contacts to the individual devices.
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73.61.Ga II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Single‐crystal x‐ray diffraction study of the InGaAs‐GaAsP/GaAs superlattice system

B‐L. Jiang, F. Shimura, G. A. Rozgonyi, N. Hamaguchi, and S. M. Bedair

Appl. Phys. Lett. 52, 1258 (1988); http://dx.doi.org/10.1063/1.99174 (3 pages) | Cited 3 times

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See Also: Erratum

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Single‐crystal x‐ray rocking curve and transmission imaging topography techniques have been used for the characterization of InGaAs‐GaAsP strained‐layer superlattices (SLS’s), which are lattice matched to GaAs substrates. The thicknesses of the SLS’s and strains, 〈ϵ⊥〉 and 〈ϵ∥〉, were readily determined nondestructively by analyzing the rocking curves obtained with Cu Kβ1 radiation. These quantitative data were combined with the qualitative defect imaging results of x‐ray topography to determine the critical intrinsic SLS thickness tISc (=PSL〈ϵ∥〉c) that dominates the generation of misfit dislocations. It was estimated for the InGaAs‐GaAsP SLS on a GaAs substrate as 1.05×10−3 Å<tISc<1.56×10−3 Å.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

CdS/p‐Si solar cells made by serigraphy

F. J. García, A. Ortíz‐Conde, and A. Sa‐Neto

Appl. Phys. Lett. 52, 1261 (1988); http://dx.doi.org/10.1063/1.99175 (3 pages) | Cited 3 times

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CdS/p‐Si solar cells have been fabricated depositing the CdS layer by serigraphy. Open circuit voltages of 538 mV, short circuit current densities of 32 mA cm−2, fill factors of 0.52, and conversion efficiencies of 8.1% have been measured under 100 mW cm−2 (AM1) simulated solar illumination.
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling

Atomic oxygen and the thermal oxidation of silicon

Andrew M. Hoff and Jerzy Ruzyllo

Appl. Phys. Lett. 52, 1264 (1988); http://dx.doi.org/10.1063/1.99676 (2 pages) | Cited 20 times

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Both molecular and atomic oxygen have been postulated to react with silicon in the thermal oxidation process. At temperatures below 700 °C very little film growth is observed in molecular oxygen. When silicon is allowed to react thermally with a flowing afterglow containing atomic oxygen an enhancement in film growth is observed. Film growth in this mode exhibits little temperature activation and is speculated to be due to a constant concentration of atomic oxygen.
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81.65.-b Surface treatments
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Changes in fracture surface composition and morphology with time in vacuum in YBa2Cu3O7−x

D. M. Kroeger, J. Brynestad, and R. A. Padgett

Appl. Phys. Lett. 52, 1266 (1988); http://dx.doi.org/10.1063/1.99677 (2 pages) | Cited 7 times

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Changes in fracture surface composition and morphology with time after fracture in a high vacuum environment are observed in the high transition temperature oxide superconductor YBa2 Cu3 O7−x . Morphological changes involving several grains and extending over distances of tens of microns are seen. Changes in fracture surface morphology are, at least in some cases, preceded by changes in surface composition as determined from Auger electron spectroscopy, and can occur at room temperature in the absence of electron beam excitation.
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74.70.-b Superconducting materials other than cuprates
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

High‐mobility variable‐density two‐dimensional electron gas in inverted GaAs‐AlGaAs heterojunctions

U. Meirav, M. Heiblum, and Frank Stern

Appl. Phys. Lett. 52, 1268 (1988); http://dx.doi.org/10.1063/1.99176 (3 pages) | Cited 44 times

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Inverted heterointerfaces (GaAs on AlGaAs), which are basic constituents of all quantum wells and superlattices, have been significantly improved using electron diffraction and a refined molecular beam epitaxy growth procedure. Utilizing them in a novel structure allowed the variation of the electron density over a wide range, with peak mobilities of 4×105 cm2/V s. The continuously variable electron density allowed comparison to a theoretical analysis of the low‐temperature scattering mechanisms, and their relation to the growth process, establishing the importance of interface charges and roughness. High‐mobility samples were used to observe the quantum Hall effect with varying carrier concentrations in a single structure.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
68.35.Fx Diffusion; interface formation
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Micropatterning of high Tc films with an excimer laser

J. Mannhart, M. Scheuermann, C. C. Tsuei, M. M. Oprysko, C. C. Chi, C. P. Umbach, R. H. Koch, and C. Miller

Appl. Phys. Lett. 52, 1271 (1988); http://dx.doi.org/10.1063/1.99678 (3 pages) | Cited 32 times

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Micron‐wide lines of high Tc Y‐Ba‐Cu‐O have been successfully patterned by ablating the films with a pulsed excimer laser. The high Tc films are mounted onto a computer‐controlled stepping stage and irradiated with a demagnified image of a variable‐size rectangular aperture. This technique has been used for fabricating features ranging from several centimeters in length to submicron in width without any degradation in Tc. For example, a superconducting microstructure of Y‐Ba‐Cu‐O, nominally 1 μm wide and 2.5 μm long, with a Tc (R=0) of 88 K and a Jc of 5×104 A/cm2 at 4.2 K was fabricated.
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74.78.-w Superconducting films and low-dimensional structures
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
79.20.Ds Laser-beam impact phenomena
74.25.Sv Critical currents
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