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7 Dec 1992

Volume 61, Issue 23, pp. 2741-2831

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Effect of In segregation on the structural and optical properties of ultrathin InAs films in GaAs

O. Brandt, L. Tapfer, K. Ploog, R. Bierwolf, and M. Hohenstein

Appl. Phys. Lett. 61, 2814 (1992); http://dx.doi.org/10.1063/1.108046 (3 pages) | Cited 21 times

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We study the segregation of In during the overgrowth of an InAs monolayer (ML) with GaAs by molecular beam epitaxy. The presence of segregating In adatoms (In floating layer) at the growth surface is observed in situ by reflection high‐energy electron diffraction. We demonstrate (i) that the segregation process causes a spatial spread‐out of 0.4 ML of In into the first 4–5 ML of the GaAs overlayer and (ii) that this spread‐out can be inhibited by the thermal desorption of the In floating layer in the initial stage of overgrowth (flash‐off). The flash‐off approach creates in fact a single InAs ML in the GaAs matrix.  
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Generation of carrier concentrations as high as 5×1019 cm−3 in GaAs by Si doping using a KrF excimer laser

K. Sugioka and K. Toyoda

Appl. Phys. Lett. 61, 2817 (1992); http://dx.doi.org/10.1063/1.108047 (3 pages) | Cited 7 times

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Extremely high carrier concentrations have been generated in GaAs by KrF excimer laser doping with Si using SiH4 gas. The carrier profile of the doped region shows a boxlike profile with a carrier concentration as high as 5×1019 cm−3 in a nonthermal equilibrium state and a depth of 170 nm. The formation of the nonthermal equilibrium state has a close connection with the transient melting and cooling process of the excimer laser doping. In addition, the thermal stability of the doped region by postannealing is investigated.
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61.72.U- Doping and impurity implantation
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
66.30.J- Diffusion of impurities
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Very low noise photodetector based on the single electron transistor

A. N. Cleland, D. Esteve, C. Urbina, and M. H. Devoret

Appl. Phys. Lett. 61, 2820 (1992); http://dx.doi.org/10.1063/1.108048 (3 pages) | Cited 24 times

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We demonstrate the use of the single electron transistor (SET) as an amplifier for a photodetector operated at 20 mK. The unparalleled low input noise of the SET permits the observation of very small numbers of charge carriers generated in a bulk p‐type Si substrate. We present data showing the response of the detector when it is illuminated by extremely low levels of red light (λ=650 nm). From the ‘‘dark current’’ noise of 0.06 e/s, we estimate a dc noise‐equivalent power NEP=2×10−21 W/√Hz for infrared light with λ=30 μm, and from this calculate a detectivity D∗=8×1017 cm⋅√Hz/W.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox

D. J. Miller, S. Sengupta, J. D. Hettinger, D. Shi, K. E. Gray, A. S. Nash, and K. C. Goretta

Appl. Phys. Lett. 61, 2823 (1992); http://dx.doi.org/10.1063/1.108049 (3 pages) | Cited 11 times

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Magnetic hysteresis data were taken from 4.2 to 35 K on Bi2Sr2CaCu2Ox samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 °C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.Nn Stacking faults and other planar or extended defects

In situ layer‐by‐layer growth of YBa2Cu3O7−x thin films by multitarget sputter deposition

K‐Y. Yang, M. S. Dilorio, S. Yoshizumi, M. A. Maung, J. Zhang, P. K. Tsai, and M. B. Maple

Appl. Phys. Lett. 61, 2826 (1992); http://dx.doi.org/10.1063/1.108050 (3 pages) | Cited 6 times

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We have fabricated YBa2Cu3O7−x thin films using in situ layer‐by‐layer sputter deposition from metal targets. Yttrium, barium, and copper metals were deposited in the atomic monolayer sequence to construct the perovskite structure in the [001] direction. X‐ray diffraction indicates that these films are c‐axis oriented with the [001] direction normal to the film surface. Smooth films with zero‐resistance transition temperature Tc0=80 K and critical current density Jc(4.2 K)∼2×107 A/cm2, measured in zero magnetic field, have been grown on LaAlO3(100) substrates. Under the conditions studied, all films have a suppressed Tc and an expanded c‐axis lattice constant, with the degree of Tc suppression inversely proportional to the lattice constant. Tc and surface morphology were shown to be sensitive to the fractional monolayer coverage ϕ during each layer’s deposition. The results suggest that films grow in the layer‐by‐layer mode as opposed to island growth.
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81.15.Cd Deposition by sputtering
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Picosecond electrical spectroscopy using monolithic GaAs circuits

Y. Konishi, M. Kamegawa, M. Case, R. Yu, M. J. W. Rodwell, R. A. York, and D. B. Rutledge

Appl. Phys. Lett. 61, 2829 (1992); http://dx.doi.org/10.1063/1.108051 (3 pages) | Cited 4 times

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This article describes an experimental apparatus for free‐space mm‐wave transmission measurements (spectroscopy). GaAs nonlinear transmission lines and sampling circuits are used as picosecond pulse generators and detectors, with planar monolithic bowtie antennas with associated substrate lenses used as the radiating and receiving elements. The received pulse is 270 mV amplitude and 2.4 ps rise time. Through Fourier transformation of the received pulse, 30–250 GHz measurements are demonstrated with ≤0.3 dB (rms) accuracy.  
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84.40.-x Radiowave and microwave (including millimeter wave) technology
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.Hi Surface barrier, boundary, and point contact devices
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