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16 Dec 1991

Volume 59, Issue 25, pp. 3207-3335

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Optically detected Auger recombinations in erbium‐ and ytterbium‐ doped InP

B. J. Heijmink Liesert, M. Godlewski, T. Gregorkiewicz, and C. A. J. Ammerlaan

Appl. Phys. Lett. 59, 3279 (1991); http://dx.doi.org/10.1063/1.105705 (3 pages) | Cited 7 times

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Microwave‐induced impact ionization of excitons and shallow donors is studied in Er‐ and Yb‐doped InP. The experimental results indicate a high efficiency of free‐electron‐related Auger recombination. Yb and Er intrashell emissions are deactivated due to an energy transfer to either free or bound carriers. A new Auger‐type nonradiative process is suggested in which the rare‐earth‐related photoluminescence decays via an energy transfer to a free carrier which has become localized via a short‐range potential.
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78.55.Cr III-V semiconductors
76.70.Hb Optically detected magnetic resonance (ODMR)
71.35.-y Excitons and related phenomena

Surface topography changes during the growth of GaAs by molecular beam epitaxy

G. W. Smith, A. J. Pidduck, C. R. Whitehouse, J. L. Glasper, A. M. Keir, and C. Pickering

Appl. Phys. Lett. 59, 3282 (1991); http://dx.doi.org/10.1063/1.105706 (3 pages) | Cited 41 times

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Changes in surface roughness taking place during (001) GaAs molecular beam epitaxy growth have been studied in situ using laser light scattering and ex situ using atomic force microscopy (AFM). Substantial increases in light scattering are found to occur firstly during oxide thermal desorption, associated with surface pit formation, and secondly during continued layer growth, due to the buildup of atomic step arrays. Monolayer height GaAs steps are readily resolved using AFM in air.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Conduction band structure of GexSi1−x using spatially resolved electron energy‐loss scattering

P. E. Batson and J. F. Morar

Appl. Phys. Lett. 59, 3285 (1991); http://dx.doi.org/10.1063/1.105707 (3 pages) | Cited 19 times

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Transmission electron energy‐loss spectroscopy has been used to follow the positions of the Δ1 and L1 conduction‐band minima, and the L3 saddle point, as a function of Ge content in GexSi1−x (x=0–0.95) alloys. By analyzing the shape of the Si 2p→conduction‐band (CB) spectra we find that L3 and Δ1 shift largely together, as the band‐structure compatibility relations predict. L1 shifts rapidly downwards with respect to Δ1 as the Ge content increases. Measurements were carried out in a scanning transmission electron microscope at a spatial resolution of better than 2 nm. Based on these results, this technique can be used to identify the composition of thin GexSi1−x alloys with a precision of better than 5%.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.66.-w Optical properties of specific thin films
68.55.-a Thin film structure and morphology

P2S5 passivation of GaAs surfaces for scanning tunneling microscopy in air

J. A. Dagata, W. Tseng, J. Bennett, J. Schneir, and H. H. Harary

Appl. Phys. Lett. 59, 3288 (1991); http://dx.doi.org/10.1063/1.105708 (3 pages) | Cited 32 times

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We report a novel method of GaAs substrate preparation which imparts significantly improved topographical and chemical uniformity to the surface. The procedure, employing an aqueous P2S5/(NH4)2S solution, leaves the surface in a highly ordered state and resistant to air oxidation for periods of a day or more without the presence of foreign chemical layer such as sulfur. Surface quality was determined by scanning tunneling microscopy (STM), time‐of‐flight secondary ion mass spectrometry, reflection high‐energy electron diffraction, and x‐ray photoelectron spectroscopy. The remarkable stability and smoothness of treated III‐V surfaces is illustrated by STM imaging of an Al0.51Ga0.49As/GaAs superlattice in air. The superlattice consisted of periodic alternating AlGaAs/GaAs layers of various thicknesses from 10 to 1000 nm.
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68.55.-a Thin film structure and morphology
81.65.-b Surface treatments
68.35.Fx Diffusion; interface formation

Selective WSi2 Schottky diodes made by rapid thermal chemical vapor deposition of WCl6

F. Trincat, J. L. Regolini, J. Mercier, and D. Bensahel

Appl. Phys. Lett. 59, 3291 (1991); http://dx.doi.org/10.1063/1.105709 (3 pages)

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Selective WSi2/Si Schottky diodes, with an ideality factor of 1.02, are obtained by limited reaction processing chemical vapor deposition at 800 °C, using WCl6 vapor diluted in H2. The deposition temperature is shown to be the most important parameter for defect formation. The diodes were fabricated on patterned and blanket wafers, and no additional thermal treatment is needed to obtain the final diode characteristics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.30.+y Surface double layers, Schottky barriers, and work functions

Light‐induced changes in hydrogenated and deuterated amorphous silicon films and solar cells

W. A. Nevin, H. Yamagishi, K. Asaoka, H. Nishio, and Y. Tawada

Appl. Phys. Lett. 59, 3294 (1991); http://dx.doi.org/10.1063/1.105710 (3 pages) | Cited 10 times

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Optical, electronic, and structural properties of high‐quality a‐Si:H and a‐Si:D films are compared. While having essentially similar electrical properties, a‐Si:D shows higher stability of the photoconductivity (σph) under illumination, and faster thermal recovery of the degraded σph. These differences may originate from differences in the Si—Si and Si—H/D bonding structures, indicated by Raman scattering and infrared measurements. In agreement, single‐junction solar cells with an intrinsic a‐Si:D layer show smaller light‐induced changes than a‐Si:H cells.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Ng Disordered solids
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.30.Hv Other nonmetallic inorganics

Sharp phosphorus spikes in silicon grown by fast gas‐switching chemical vapor deposition at reduced and atmospheric pressure

P. J. Roksnoer, J. W. F. M. Maes, A. T. Vink, C. J. Vriezema, and P. C. Zalm

Appl. Phys. Lett. 59, 3297 (1991); http://dx.doi.org/10.1063/1.105711 (3 pages) | Cited 2 times

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Sharp phosphorus doping spikes in silicon were grown by fast‐gas‐switching chemical vapor deposition at temperatures between 800 and 850 °C using disilane and phosphine in 0.03, 0.1, and 1 atm hydrogen carrier gas. The phosphine doping gas was added while growing silicon at a rate of 0.15–0.5 nm/s. High depth resolution secondary ion mass spectrometry measurements have revealed sharp and high concentration dopant profiles. Peak phosphorus concentrations up to 7×1019 cm−3 and a full width at half maximum of 7 nm were obtained. Electrical measurements show that at these concentrations about 40% of the dopant atoms is electrically active in structures grown at 1 atm. Formation of doping tails is shown to be suppressed at atmospheric hydrogen pressure.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.uf Ge and Si
72.80.Cw Elemental semiconductors

Fermi level pinning at epitaxial Si on GaAs(100) interfaces

J. A. Silberman, T. J. de Lyon, and J. M. Woodall

Appl. Phys. Lett. 59, 3300 (1991); http://dx.doi.org/10.1063/1.105712 (3 pages) | Cited 7 times

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GaAs Schottky barrier contacts and metal‐insulator‐semiconductor structures that include thin epitaxial Si interfacial layers operate in a manner consistent with an unpinned Fermi level at the GaAs interface. These findings raise the question of whether this effect is an intrinsic property of the epitaxial GaAs(100)‐Si interface. We have used x‐ray photoemission spectroscopy to monitor the Fermi level position during in situ growth of thin epitaxial Si layers. In particular, films formed on heavily doped n‐ and p‐type substrates were compared so as to use the large depletion layer fields available with high impurity concentration as a field‐effect probe of the interface state density. The results demonstrate that epitaxial bonding at the interface alone is insufficient to eliminate Fermi level pinning, indicating that other mechanisms affect the interfacial charge balance in the devices that utilize Si interlayers.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

High detectivity InGaAs base infrared hot‐electron transistor

K. K. Choi, L. Fotiadis, M. Taysing‐Lara, W. Chang, and G. J. Iafrate

Appl. Phys. Lett. 59, 3303 (1991); http://dx.doi.org/10.1063/1.105713 (3 pages) | Cited 19 times

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An infrared hot‐electron transistor with a thin (300 Å)InGaAs base layer is constructed. By adopting a thin base material with a large Γ‐L valley separation, the photocurrent transfer ratio is improved by a factor of four in comparison with the GaAs base transistor. As a result, the detectivity of the transistor is increased to 1.4×1010 cm√Hz/W at 77 K with a cutoff wavelength of 9.5 μm, two times as large as the companion state‐of‐the‐art GaAs quantum well photoconductor. Combined with the lower dark current, the voltage responsivity and the noise equivalent temperature difference of a detector array can be improved by more than an order of magnitude.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Photoluminescence characterization of pseudomorphic modulation‐doped quantum wells at high carrier sheet densities

Steven K. Brierley, William E. Hoke, Peter S. Lyman, and Henry T. Hendriks

Appl. Phys. Lett. 59, 3306 (1991); http://dx.doi.org/10.1063/1.105714 (3 pages) | Cited 14 times

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A systematic study has been made of the photoluminescence spectra of modulation‐doped strained‐layer quantum wells at high electron sheet densities. Peaks associated with both the n=1 and n=2 electron subbands are observed, and the relative intensities are shown to be a result of the symmetry properties of the quantum wells. It is demonstrated that only the full width half maximum of the n=2 subband peak is useful for characterizing high carrier densities.
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78.55.Cr III-V semiconductors
73.61.Ey III-V semiconductors

Highly conductive ultrathin crystalline Si layers by thermal crystallization of amorphous Si

R. Kakkad, S. J. Fonash, and S. Weideman

Appl. Phys. Lett. 59, 3309 (1991); http://dx.doi.org/10.1063/1.105715 (3 pages) | Cited 4 times

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Ultrathin, highly conductive polycrystalline Si films have been produced on glass by crystallization of 200 Å a‐Si films. The films, which result from our relatively low‐temperature process (e.g., 700 °C/4 min), are completely crystallized with grain sizes of the order of 1 μm for doped films. Both n‐ and p‐type Si films of high conductivity (∼102 S/cm) can be obtained by this process. These 200 Å crystallized films, produced from doped a‐Si:H precursors, are over 10 orders of magnitude more conductive than deposited microcrystalline Si films of the same thickness. The high conductivities in these ultrathin films on glass make them very attractive for applications in photodetector and solar cell structures.
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73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Dielectric properties of nonsquare AlGaAs/GaAs single quantum wells at photon energies below the band gap

E. Herbert Li and Bernard L. Weiss

Appl. Phys. Lett. 59, 3312 (1991); http://dx.doi.org/10.1063/1.105716 (3 pages) | Cited 3 times

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The complex dielectric function of square and hyperbolic AlGaAs/GaAs single quantum wells have been calculated to predict the refractive index differences at photon energies below the band gap. The results show that, at these photon energies, the refractive index of a single hyperbolic quantum well exceeds that of the as‐grown square quantum well during the initial stages of disordering, after which it decreases with increasing disorder. These results also predict the onset of antiguiding in multiple quantum well waveguides, which has been observed previously.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Scaling the Si metal‐oxide‐semiconductor field‐effect transistor into the 0.1‐μm regime using vertical doping engineering

R. H. Yan, A. Ourmazd, K. F. Lee, D. Y. Jeon, C. S. Rafferty, and M. R. Pinto

Appl. Phys. Lett. 59, 3315 (1991); http://dx.doi.org/10.1063/1.105717 (3 pages) | Cited 14 times

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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.  
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85.30.Tv Field effect devices
85.40.Bh Computer-aided design of microcircuits; layout and modeling
85.30.De Semiconductor-device characterization, design, and modeling
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

High electron mobility in modulation‐doped Si/SiGe quantum well structures

G. Schuberth, F. Schäffler, M. Besson, G. Abstreiter, and E. Gornik

Appl. Phys. Lett. 59, 3318 (1991); http://dx.doi.org/10.1063/1.105718 (3 pages) | Cited 23 times

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Modulation‐doped multiple quantum well structures based on Si/SiGe have been grown by molecular beam epitaxy. Low‐temperature electron mobilities up to 17 000 cm2/V s have been achieved in narrow Si quantum wells. The electronic properties of the strain symmetrized Si/SiGe multilayer structures were studied by magnetotransport and cyclotron resonance experiments. The results are consistent with subband calculations which take the strain‐induced splitting of the conduction band and the lowering of two valleys into account.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Surface reconstruction limited mechanism of molecular‐beam epitaxial growth of AlGaAs on (111)B face

Toshiro Hayakawa, Mitsukata Morishima, and Samuel Chen

Appl. Phys. Lett. 59, 3321 (1991); http://dx.doi.org/10.1063/1.105719 (3 pages) | Cited 19 times

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We propose a model which gives a fundamental limiting factor for the growth of epilayers on (111)B face. Our model is that the As‐trimer structure of As‐stabilized (111)B surface with the (2×2) reconstruction disturbs the incorporation of group III atoms into lattice sites. This model gives the explanation to most of the reported properties in the growth of GaAs and AlGaAs on (111)B substrates. This model has been verified by comparing the growth rate of GaAs layers grown by molecular‐beam epitaxy over mesa‐shaped substrates with (111)A and (111)B sidewalls using As4 and As2. Moreover, the cause of microtwins found in transmission electron microscopy images of AlGaAs grown on (111)B GaAs at a low Ts can be at least partly explained by this model.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.Ja Surface and interface dynamics and vibrations

Molecular beam epitaxial growth of InAsSb strained layer superlattices. Can nature do it better?

I. T. Ferguson, A. G. Norman, B. A. Joyce, T‐Y. Seong, G. R. Booker, R. H. Thomas, C. C. Phillips, and R. A. Stradling

Appl. Phys. Lett. 59, 3324 (1991); http://dx.doi.org/10.1063/1.105720 (3 pages) | Cited 32 times

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Molecular beam epitaxial growth of a normally homogeneous InAs0.5Sb0.5 alloy below 430 °C results in its coherent phase separation into platelets of two different alloy compositions with tetragonally distorted crystal lattices. This produces a ‘‘natural’’ strained layer superlattice (n‐SLS) with clearly defined interfaces modulated in the [001] growth direction. A description of the n‐SLS growth mode in InAsSb is outlined, and the optical response of a n‐SLS structure, which extends to 12.5 μm−considerably further than that of a homogeneous InAs0.5Sb0.5 layer (8.9 μm)−is reported.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
72.40.+w Photoconduction and photovoltaic effects

Study of the oxygen depletion in the film‐substrate interface of superconducting YBa2Cu3O7−x films

J. Colino, J. L. Sacedón, and J. L. Vicent

Appl. Phys. Lett. 59, 3327 (1991); http://dx.doi.org/10.1063/1.106397 (3 pages) | Cited 6 times

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Auger electron spectroscopy (AES) depth profiles were carried out on c‐axis oriented YBa2Cu3O7−x films grown in situ onto SrTiO3 (100) and polycrystalline yttria‐stabilized zirconia substrates. These films were grown by on‐axis single‐target dc planar magnetron sputtering, and they show zero resistance as high as 90.2 K and critical currents above 105 A/cm2 (77 K). The AES depth profiles reveal a clear oxygen loss at the interface. This oxygen deficiency corresponds to an atomic decrease from 7 to 6.6–6.3 per unit cell, in good agreement with the tetragonal structure oxygen composition. This confirms the oxygen‐deficient first stages of YBa2Cu3O7−x film growth on some usual cubic substrates, and that those first layers do not become fully oxidized after the oxygen intake on the cooling in O2 atmosphere.
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74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology

Enhanced quantum interference effects in parallel Josephson junction arrays

J. H. Miller, G. H. Gunaratne, J. Huang, and T. D. Golding

Appl. Phys. Lett. 59, 3330 (1991); http://dx.doi.org/10.1063/1.105721 (3 pages) | Cited 20 times

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We have calculated the total critical current as a function of applied magnetic flux for a superconducting interferometer consisting of many Josephson junctions in parallel. An enhancement and narrowing of the periodic principal maxima in the critical current versus flux characteristic is predicted as the number of junctions in parallel increases, even when the effects of finite self‐ and mutual inductances and nonuniformity of the junction critical currents are included in the calculations. The possible application of the superconducting quantum interference grating, or SQUIG, for the detection of magnetic flux is discussed.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
85.25.Cp Josephson devices

Transient electric field generated by nonequilibrium states in superconducting Pb films

Xin‐Hua Hu, T. Juhasz, and W. E. Bron

Appl. Phys. Lett. 59, 3333 (1991); http://dx.doi.org/10.1063/1.105722 (3 pages) | Cited 4 times

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Nonequilibrium states can be excited in superconducting Pb films with laser pulses of picosecond duration. We used the technique of electro‐optic sampling to observe the transient electric field generated by these states in the presence of a supercurrent. It follows from our experiment that the switching between the superconducting and normal states occurs within 1 ps after the laser excitation.
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74.25.N- Response to electromagnetic fields
74.40.-n Fluctuation phenomena
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
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