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23 Jul 1990

Volume 57, Issue 4, pp. 321-413

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Thermal stability of coevaporated Al‐Pt thin films on GaAs substrates

B. Blanpain, G. D. Wilk, J. O. Olowolafe, J. W. Mayer, and L. R. Zheng

Appl. Phys. Lett. 57, 392 (1990); http://dx.doi.org/10.1063/1.103671 (3 pages) | Cited 7 times

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We report on the stability of Al‐Pt coevaporated thin films on GaAs substrates for aluminum concentrations ranging from 45 to 70 at. %. We show that for the region with compositions between AlPt and Al2Pt these alloy thin films fulfill the thermal stability requirements imposed by GaAs self‐aligned gate technology.
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68.60.Dv Thermal stability; thermal effects
68.35.Md Surface thermodynamics, surface energies
68.55.Nq Composition and phase identification
73.40.Ns Metal-nonmetal contacts

Determination of the density of states effective mass and the energy minimum of the X7 satellite conduction band in GaAs from the X6→X7 absorption spectrum

W. B. Wang, N. Ockman, M. A. Cavicchia, and R. R. Alfano

Appl. Phys. Lett. 57, 395 (1990); http://dx.doi.org/10.1063/1.103673 (3 pages) | Cited 8 times

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A time‐resolved picosecond pump‐infrared‐probe technique was used to measure the X6→X7 absorption spectrum in an intrinsic GaAs crystal. From the long‐wavelength onset of the induced X6→X7 absorption spectrum, the energy gap between the minima of the X6 and X7 bands was directly determined to be 0.345±0.017 eV. By fitting the experimental data, the density of states effective mass for the X7 band was found to be 0.48±0.06m0.
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78.30.Fs III-V and II-VI semiconductors
71.20.-b Electron density of states and band structure of crystalline solids
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Carbon concentration dependence of charged point‐defect density in semi‐insulating GaAs as observed by nuclear magnetic resonance

Maki Suemitsu, Masaaki Nishijima, and Nobuo Miyamoto

Appl. Phys. Lett. 57, 398 (1990); http://dx.doi.org/10.1063/1.103674 (2 pages) | Cited 2 times

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A newly developed method [J. Appl. Phys. 66, 3178 (1989)] in nuclear magnetic resonance (NMR) spin‐echo measurements, which allows us a precise determination of the quadrupolar interaction magnitude in crystals, has been applied to a series of undoped, liquid‐encapsulated Czochralski GaAs crystals. By varying the carbon concentration from 6×1014 to 1.4×1016 cm−3, it was verified that the quadrupolar interaction magnitude is proportional to the density of charged point defects in the crystal. The NMR method provides a feasible tool to detect ionized point defects of the order of as low as 1014 cm−3.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
71.55.Eq III-V semiconductors
76.60.Lz Spin echoes

Atomic layer epitaxy of AlGaAs

J. R. Gong, D. Jung, N. A. El‐Masry, and S. M. Bedair

Appl. Phys. Lett. 57, 400 (1990); http://dx.doi.org/10.1063/1.103675 (3 pages) | Cited 8 times

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Atomic layer epitaxy (ALE) has been employed to grow AlGaAs in the temperature range 550–700 °C. Monolayer growth was achieved independent of the column III flux. Al incorporates during ALE more efficiently than in metalorganic chemical vapor deposition (MOCVD). The ALE films grown at low temperature have superior photoluminescence properties when compared with the MOCVD‐grown films. The as‐grown ALE films are p type with carrier concentrations in the 1017–1019/cm3 range, depending on the growth conditions.
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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.)
78.55.Cr III-V semiconductors

Extremely high‐selective electron cyclotron resonance plasma etching for phosphorus‐doped polycrystalline silicon

Seiji Samukawa, Yasuhiro Suzuki, and Masami Sasaki

Appl. Phys. Lett. 57, 403 (1990); http://dx.doi.org/10.1063/1.103649 (3 pages) | Cited 10 times

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Extremely high‐selective etching for phosphorus‐doped polycrystalline silicon is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. The selectivity ratio (phosphorus‐doped polycrystalline silicon etching rate/SiO2 etching rate) is around 100 at 5×10−4 Torr and 260 at 3×10−3 Torr. Furthermore, the polycrystalline silicon etching rate is more than 3000 Å/min in pure Cl2 etching gas with no rf bias under the above selectivity ratio conditions. The high etching selectivity ratio is generated by low ion energy due to no rf bias power and small magnetic field divergence. The high etching rate is achieved by high ion current density at the ECR position in the plasma chamber.
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81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer
52.40.Hf Plasma-material interactions; boundary layer effects

Low‐noise high‐speed dc superconducting quantum interference device magnetometer with simplified feedback electronics

D. Drung, R. Cantor, M. Peters, H. J. Scheer, and H. Koch

Appl. Phys. Lett. 57, 406 (1990); http://dx.doi.org/10.1063/1.103650 (3 pages) | Cited 82 times

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A dc superconducting quantum interference device (SQUID) magnetometer has been integrated on a 9×9 mm2 chip with eight pick‐up loops in parallel to directly form a SQUID inductance of about 0.5 nH. Very simple feedback electronics have been developed which do not require liquid‐helium temperature impedance matching circuits or flux modulation techniques. The magnetometer has a typical white noise of 8 fT/(Hz)1/2 and a 1/f  corner frequency below 3.5 Hz. With an additional positive feedback circuit at 4.2 K the white noise level has been further reduced to 4.5 fT/(Hz)1/2. Using a two‐pole integrator, a 3 dB bandwidth around 0.5 MHz and a maximum slew rate of 3 mT/s at 1.3 kHz have been attained with a ±0.4 μT feedback range.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
07.55.-w Magnetic instruments and components

Microwave surface resistance of epitaxial YBa2Cu3O7 thin films on sapphire

K. Char, N. Newman, S. M. Garrison, R. W. Barton, R. C. Taber, S. S. Laderman, and R. D. Jacowitz

Appl. Phys. Lett. 57, 409 (1990); http://dx.doi.org/10.1063/1.103651 (3 pages) | Cited 65 times

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Microwave surface resistance data were measured on pairs of YBa2Cu3O7 thin films on Al2O3 {1102} substrates by a parallel plate resonator technique. The surface resistance Rs at 10 GHz was 65 μΩ at 10 K and 850 μΩ at 77 K. These epitaxial YBa2Cu3O7 films were grown on 500‐Å‐thick buffer layers of SrTiO3. X‐ray diffraction data showed that the YBCO thin films with the SrTiO3 buffer layers have better in‐plane epitaxy than those without such buffer layers. Critical current density of 2×106 A/cm2 at 74 K was measured by the ac mutual inductance response of the films. The improved microwave surface resistance and the higher critical current density are believed to be the results of better in‐plane epitaxy.
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74.78.-w Superconducting films and low-dimensional structures
74.25.N- Response to electromagnetic fields

Fe/Fe‐N multilayer films with low coercivity zero magnetostriction and high saturation magnetization

K. K. Shih, M. E. Re, and D. B. Dove

Appl. Phys. Lett. 57, 412 (1990); http://dx.doi.org/10.1063/1.103652 (2 pages) | Cited 12 times

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A method of fabricating of Fe/Fe‐N multilayer films in the form of alternating thin films of Fe separated by very thin interlayers of Fe‐N sputtered in the presence of nitrogen is described. It was found that the properties of these films depended on the thickness of Fe and Fe‐N layers and the bias voltage. There is a region where the composite films have coercivity less than 1 Oe, with zero or near‐zero magnetostriction. The normally high saturation magnetization of Fe with value of 20 kG was preserved.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
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